JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36521 MGN-1 8/21/90 After traveling over 1.2 billion kilometers (780,000,000 miles), the Magellan spacecraft was inserted into orbit around Venus on August 10, 1990. This mosaic consists of adjacent pieces of two Magellan image strips obtained on August 16, 1990 in the first radar test. The radar test was part of a planned In-Orbit Checkout sequence designed to prepare the Magellan spacecraft and radar to begin mapping after August 31, 1990. The strip on the left was returned to the Goldstone Deep Space Station in California, the strip on the right was received at the Deep Space Station in Canberra, Australia. A third station that will be receiving Magellan data is located near Madrid, Spain. Each image strip is 20 km (12 miles) wide and 16,000 km (10,000 miles) long; this mosaic is a small portion 80 km (50 miles) long. This image is centered at 21 degrees North latitude and 286.8 degrees East longitude, southeast of a volcanic highland region called Beta Regio. The resolution of the image is about 120 meters (400 feet), 10 times better than previous images of the same area of Venus, revealing many new geologic features. The bright line trending NW-SE across the center of the image is a fracture or fault zone cutting the volcanic plains. In the upper left corner of the image, a multiple-ring circular feature of probable volcanic origin can be seen, approximately 4.27 km (2.65 miles) across. The bright and dark variations seen in the plains surrounding these features correspond to volcanic lava flows of varying ages. The volcanic lava flows in the southern half of the image have been cut by N-S trending faults. This area is similar geologically to volcanic deposits seen on the Earth at Hawaii and the Snake River Plains in Idaho, USA. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36522 MGN-2 8/21/90 This portion of a Magellan radar image strip shows a small region on Venus 20 km (12.4 miles) wide and 75 km (50 miles) high, on the east flank of a major volcanic upland called Beta Regio. The image is centered at 23 degrees North latitude and 286.7 degrees East longitude. The ridge and valley network in the middle part of the image is formed by intersecting faults which have broken the Venusian crust into a complex deformed type of surface called tessera, the Latin word for tile. The parallel mountains and valleys resemble the Basin and Range Province in the Western United States. The irregular dark patch near the top of the image is a smooth surface, probably formed by lava flows in a region about 10 kilometers (6 miles) across. Similar dark surfaces within the valleys indicate lava flows that are younger than the tessera giving an indication of the geologic time relationships of the events that formed the present surface. The image has a resolution of 120 meters (400 feet). JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36523 MGN-3 8/21/90 This image shows a comparison between a Magellan image (right) and the highest resolution Earth-based radar image of Venus, obtained by the U. S. National Astronomy and Ionosphere Center Arecibo Observatory in Puerto Rico. The small white box in the Arecibo image on the left corresponds to the Magellan image. This portion of a Magellan radar image strip shows a small region on the east flank of a major volcanic upland called Beta Regio. The image is centered at 23 degrees North latitude and 286.7 degrees East longitude. The ridge and valley network in the mid part of the image is formed by intersecting faults which have broken the Venusian crust into a complex deformed type of surface called tessera, the Latin word for tile. The parallel mountains and valleys resemble the Basin and Range Province in the western United States. The irregular dark patch near the top of the image is a smooth surface, probably formed by lava flows in a region about 10 kilometers (6 miles) across. Similar dark surfaces within the valleys indicate lava flows that are younger than the tessera. The Arecibo image contains probable impact craters, many faults, volcanic flows, and tessera regions that will be mapped in detail by Magellan. The Magellan image has a resolution of 120 meters (400 feet). The image segment is 20 km wide (12.4 miles) and 150 km (90 miles) long. The Arecibo image has a resolution of 1-3 km (0.6-1.8 miles) and is approximately 900 km (550 miles) across. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36529 8/21/90 Multiple fracture systems in Devana Chasma, Phoebe Regio area. These fractures are in the central rift trough of Devana. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36530 8/21/90 Tessera region east of Beta Regio. Tessera is formed here by two orthogonal fault systems. The flows of the wider graben are covered by more recent lava flows. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36531 8/21/90 Fracture system extending north from Devana Chasma. Same as #27. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36532 8/21/90 Devana Chasma at 6 degrees north latitude, 288 degrees east longitude. Steep walled fault troughs called graben indicate that this region is being pulled apart forming a complex rift valley extending south from Beta Regio. Volcanic flows appear to cover the flat floors of the graben in several places. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36533 8/21/90 Arecibo radar image (left) compared to Magellan. Theia Mons in Beta Regio is seen in the upper left corner of the Arecibo image. The white line shows the location of the Magellan image strip. Magellan reveals a network of intersecting fractures extending north from Devana Chasma. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36545 MGN-4 8/23/90 This Magellan image mosaic shows the impact crater Golubkina, first identified in Soviet Venera 15/16 data. The crater is named after Anna Golubkina (1864-1927), a Soviet sculptor. The crater is about 34 km (20.4 miles) across, similar to the size of the West Clearwater impact structure in Canada. The crater Golubkina is located at about 60.5 degrees north latitude, 287.2 degrees east longitude. Magellan data reveal that Golubkina has many characteristics typical of craters formed by a meteorite impact including terraced inner walls, a central peak, and radar-bright rough ejecta surrounding the crater. The extreme darkness of the crater floor indicates a smooth surface, perhaps formed by the ponding of lava flows in the crater floor as seen in many lunar impact craters. The radar- bright ejecta surrounding the crater indicates a relatively fresh or young crater. Craters with central peaks in the Soviet data range in size from about 10-60 km (6-36 miles) across. The largest impact crater identified in the Soviet Venera data is 140 km (84 miles) in diameter. This Magellan image strip is approximately 20 km (12 miles) wide and this piece of the image is approximately 100 km (62 miles) high. The image is a mosaic of two orbits obtained in the first Magellan radar test and played back to Earth to the Deep Space Stations near Goldstone, California and Canberra, Australia, respectively. The resolution of this image is approximately 120 meters (400 feet). The see-saw margins result from the offset of individual radar frames obtained along the orbit. The spacecraft moved from the north (top) to the south, looking to the left. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36546 MGN-5 8/23/90 Two mosaicked pieces of Magellan image strips display the area east of the Rhea Mons volcano on Venus. This image is centered at about 32.5 degrees north latitude and 286.6 degrees east longitude. The mosaic is 47 km (28 miles) wide and 135 km (81 miles) long. This region has been previously identified as "tessera" from Earth-based radar (Arecibo) images. The center of the image is dominated by a network of intersecting ridges and valleys. The radar-bright north-south trending features in this image range from 1 km (0.6 miles) to 3 km (1.8 miles) in length. The average spacing between these ridges is about 1.5 km (0.9 miles). The dark patches at the top of the image are smooth surfaces and may be lava flows located in lowlands between the higher ridge and valley terrain. This image is a mosaic of two orbits obtained in the first Magellan radar test and played back to Earth to the Deep Space Stations near Goldstone, California and Canberra, Australia, respectively. The resolution of this image is approximately 120 meters (400 feet). JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36547 MGN-6 8/23/90 This three-dimensional representation of brightness variations in a Magellan radar image of Golubkina crater enhances the structural features of the crater. Golubkina is 34 km (20.4 miles) in diameter, and is located at about 60.5 degrees north latitude, 287.2 degrees east longitude. Golubkina is characterized by terraced inner walls and a central peak, typical of large impact craters on the Earth, Moon and Mars. The terraced inner walls form at late stages in the formation of an impact crater, due to collapse of the initial cavity formed by the meteorite impact. The central peak forms due to rebound of the inner crater floor. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36548 MGN-7 8/23/90 This image of the Venusian crater, Golubkina, a 34 km (20.4 miles) diameter impact crater located at about 60.5 degrees north latitude, 287.2 degrees east longitude, contains Magellan data mosaicked with a Soviet Venera 15/16 radar image of the same feature. The Magellan part of the image (right) reveals details of the geology of the crater such as the central peak, the inner terraced walls, and the extremely smooth floor of the crater. The smoothness of the floor may be due to ponding of volcanic lava flows in the crater floor. The rough, blocky morphology of the crater ejecta and the sharp terraced crater wall suggest that this feature is relatively young. The Soviet data have a resolution of 1-2 km (0.6-1.2 miles); the Magellan data have a resolution of about 120 meters (400 feet). JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36611 MGN-8 9/12/90 Magellan radar image of part of the Phoebe region of Venus. Mosaic of part of revs 146 and 147 acquired in the first radar test on August 16, 1990. The image is located at 292 degrees E. longitude, 24 degrees south latitude. This image is 30 km (19.6 miles) wide and 70 km (43.5 miles) high. This Magellan radar image of Venus shows an area to the southeast of Phoebe Regio, an upland region characterized by major rift zones. The irregular- shaped depressions near the middle of the image are interpreted as volcanic calderas, the larger of which is 8 x 3.6 km (5 x 2.2 miles) across. Unlike impact craters, volcanic calderas are not usually circular in map view. Irregular calderas such as these occur on basaltic shield volcanoes on Earth, such as those in Hawaii. The radar illumination comes from the left causing the caldera walls that face the spacecraft to be brightly illuminated. Another factor that makes the walls bright is that the walls may be rough and blocky. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36612 MGN-9 9/12/90 Magellan radar image of part of the Phoebe region of Venus. Mosaic of part of revs 146 and 147 acquired in the first radar test on August 16, 1990. The image is located at 291 degrees E. longitude, 19 degrees south latitude. This image is 30 km (19.6 miles) wide and 76 km (47 miles) high. On the basis of Pioneer Venus and Arecibo data, it is known that two major rift zones occur in Southern Phoebe Regio and that they terminate at about 20-25S latitude about 2000 km apart. This image is just north of the southern end of the western rift zone. This region is characterized by a complex geologic history involving both volcanism and faulting. Several of the geologic units show distinctive overlapping or cross-cutting relationships that permit identification and separation of geologic events and construction of the geologic history of the region. The oldest rocks in this image form the complexly deformed and faulted, radar bright, hilly terrain in the northern half. Faults of a variety of orientations are observed. A narrow fault trough (about one- half to one km wide) is seen crossing the bright hills near the lower part in the middle of the image. This is one of the youngest faults in the faulted, hilly unit as it is seen to cut across many other structures. The fault trough in turn appears to be embayed and flooded by the darker plains that appear in the south half of the image. These plains are interpreted to be of volcanic origin. The dark plains may be formed of a complex of overlapping volcanic flows. For example, the somewhat darker region of plains in the lower left (SW) corner of the image may be a different age series of plains-forming volcanic lava flows. Finally, the narrow bright line crossing the image in its lower part is interpreted to be a fault which crosscuts both plains units and is thus the youngest event in the sequence. These relationships show the interplay of volcanic activity and faulting that have influenced this region and a number of other regions on Venus. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36613 MGN-10 9/12/90 Magellan radar image of part of the Phoebe region of Venus. Mosaic of part of revs 146 and 147 acquired in the first radar test on August 16, 1990. The image is located at 291 degrees E longitude, 20 degrees south latitude. This image is 30 km (19.6 miles) wide and 76 km (47 miles) high. This Magellan image shows a broad, up to 17 km (11 miles) wide, radar- bright, lobate lava flow that extends 25 km NW across the image strip. The volcanic flow appears bright in this image because it is rough on a scale of a few centimeters to a few meters (a few inches to a few yards), much like lava flows on Earth that are called by geologists, aa (ah-ah), a Hawaiian word that probably mimics the sound the ancients uttered while running barefoot over the rough, jagged surface. It is located near the SE flank of Phoebe Regio and has flowed into local topographic lows. This lava flow has flooded the darker plains and appears to have buried N-S trending lineaments that cut the darker material. No obvious volcanic sources are visible in this image. The flow has a markedly uniform surface texture in contrast to the more mottled texture of adjacent deposits; this suggests it may represent the most recent in a series of eruptions that subsequently have been obscured. To the north and south are NW trending graben that may belong to the system of fractures associated with Phoebe Regio. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36642 MGN-11 9/17/90 On September 15, 1990, the Magellan spacecraft started radar operations for its mapping mission at Venus. This image is taken from the first set of radar data collected in the normal operating mode. This Magellan radar image is of an impact crater in the Navka Region of Venus. The image is a mosaic of data taken from orbits 376 and 377 on September 15, 1990. The crater is located at 334.5 E. longitude, 21.4 S. latitude, and is about 9 x 12 kilometers (5 x 7 miles) in size. This crater is very unusual, and is in some ways different from anything seen elsewhere in the solar system. It is fresh, with a sharp rim, terraces on the walls, and a well-developed ejecta blanket. The rim, however, is distinctly kidney-shaped rather than circular, and the crater's fresh appearance suggests, that it formed with that shape at impact. The ejecta blanket is markedly non-symmetric, with lobes extending to the north (top) and south (bottom) of the image, and a major extension stretching to the east (right). On the crater floor are several smooth, flat, dark regions. The asymmetric shape of the ejecta blanket has been observed on other planets and in impact experiments, and probably indicates that the impactor struck the surface at a low, oblique angle. The impactor would have been moving from west to east, sending ejecta lobes off to either side and a long streamer in the forward direction. The truly unusual aspect of the crater is its shape. One possible explanation is that the impactor broke up as it passed through the dense Venusian atmosphere, causing several large chunks of material to strike the surface almost simultaneously in an irregular pattern. The dark patches on the crater floor may be solidified pools of molten rock generated by the impact, or could be volcanic material extruded some time after the crater's formation. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36643 MGN-13 9/17/90 On September 15, 1990, the Magellan spacecraft started radar operations for its mapping mission at Venus. This image is taken from the first set of radar data collected in the normal operating mode. This Magellan radar image is of part of the Danu Montes in the Lakshmi Region of Venus. The mosaic is part of orbits 376, 377, and 378 acquired on the first day of nominal mapping, September 15, 1990. The image is located at 329.6 degrees E longitude and 58.75 degrees N latitude. This image is 40 kilometers (19.6 miles) wide and 60 kilometers (39.2 miles) high. Danu Montes is a mountain belt located at the southern edge of the Ishtar Terra highland region. It rises one to three kilometers above a flat plain to the north known as Lakshmi Planum. Lakshmi Planum contains several large volcanoes and abundant plains of volcanic origin. To the south of Danu Montes is a scarp (Vesta Rupes) marking the southern edge of Western Ishtar Terra. At the scarp the topography descends about two kilometers to the surrounding lowlands. On the basis of Pioneer Venus, Arecibo, and Venera data, Danu Montes and the other mountain belts surrounding Lakshmi Planum have been interpreted to be orogenic belts marking the focus of compressional deformation, much like the Appalachians and Andes on Earth. In the upper right part of this image, relatively bright, smooth-textured plains of Lakshmi Planum are seen to embay the heavily deformed mountain region to the south. In the mountain range south of these plains the geology is dominated by abundant faults at multiple angles and showing various cross- cutting relationships. In the northern part of the mountain the surface is dominated by sinuous, west-northwest trending troughs less than a kilometer (0.6 miles) in width, separated by narrow, flat regions. Further south are flat-floored features similar to extensional graben on Earth. These graben are up to 2 kilometers (1.3 miles) in width. The prominent bright and dark feature trending across the bottom part of the image is a linear trough about 5 kilometers wide (3.1 miles) located near the crest of the mountain range. South of the mountain crest, additional deformation is seen trending both parallel and perpendicular to the structures in other parts of the mountain belt. These patterns represent the complex tectonic deformation involved in the formation of the mountain ranges, and the graben-like features may represent extension associated with the gravitational collapse of the mountains subsequent to their initial formation. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36644 MGN-12 9/17/90 On September 15, 1990, the Magellan spacecraft started radar operations for its mapping mission at Venus. This image is taken from the first set of radar data collected in the normal operating mode. These fault-bounded troughs were imaged by Magellan on orbit 147 on September 15, 1990. The image is of part of the Lavinia Region of Venus at 60 degrees south latitude, 347 degrees east longitude. The image is 28 kilometers (17 miles) wide and 75 kilometers (46 miles) long. This region is at the intersection of two tectonic trends. An extensive set of east-west trending fractures extends to the west (left) and a second set extends down to the south-southeast (lower right). The lines of pits suggest some igneous or volcanic activity accompanying the faulting. The prominent trough trending diagonally across the image is 5 kilometers (3.1 miles) wide and is 100 to 200 meters (300 to 600 feet) deep. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36655 9/19/90 This image is part of the Helen Region of Venus. The image was obtained by the Magellan radar on August 16, 1990 during a radar test. The location is at 26.1 degrees south latitude, 292 degrees east longitude. The image segment is 47 kilometers (29 miles) wide and 77 kilometers (48 miles) in length. This area illustrates the complex nature of some of the plains. At least two directions of faulting can be seen in the bright linear patterns. The cross fracture pattern is usually associated with high relief, rugged terrain of tessera regions. In this location, however, there appears to be little relief associated with the fracturing. A clue to the interpretation of this region lies in the numerous circular to irregular depressions ranging in size from 500 m (0.3 mile) to 1.5 kilometer (0.9 mile). These depressions appear to be volcanic calderas and are probably associated with extensive volcanic flows that have flooded the tessera. Another probable volcanic feature is the small mound approximately 1.9 kilometer (1.2 mile) in diameter on the right side of the picture in the lower half. The bright lines can be interpreted as fracture or fault traces. The fact that they tend to occur in pairs of lines spaced 500 m (0.3 miles) to 1.5 kilometer (0.9 miles) apart suggest that the lines delineate flooded graben, or fault valleys that have been filled with volcanic flows. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36656 9/19/90 This view of the surface of Venus acquired by the Magellan spacecraft shows a geologically young region of lowland plains. The location is near the equator between two highland areas known as Asteria Regio and Phoebe Regio. Illumination in the radar image is from the left (west); in this transformed version the viewer looks due north with a slant angle about 10 degrees. The region seen is about 40 kilometers (24 miles) wide and stretches 600 kilometers (360 miles) down range to the north. Complex canyon systems that trend northeast and northwest were produced as Venus' crust was pulled apart by extensional forces. Some were filled with younger lava flows. The canyons are typically 5 to 10 kilometers (3 to 6 miles) wide, 50 to 100 kilometers (30 to 60 miles) long and rimmed by fault scarps a hundred meters or so high. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36657 9/19/90 This mosaic is made up from Magellan orbits 146 and 147, obtained on August 16, 1990 in the Helen region of the southern hemisphere of Venus and centered at 36.5 degrees south latitude, 293.3 degrees longitude. Resolution of the Magellan data is about 120 meter (400 feet). The mosaic is about 40 kilometers (24 miles) wide and about 80 kilometers (50 miles) long, and shows a portion of a corona in a highland region called Themis Regio. Coronae are large [>250 kilometers (150 miles) across] circular structures surrounded by a ring of ridges. Coronae were first identified in Soviet radar images of Venus. Coronae usually average about 1 kilometer (0.6 mile) high, and are thought to form due to the rise of hot material from the interior of the planet, similar to Hawaii on the Earth. The mosaicked Magellan images show the interior of the corona and a portion of its rim. Ridges appear to radiate out from the center of the corona, perhaps produced due to extensional stresses caused by uplift of the surface. Geologists and geophysicists will be analyzing the morphology, spacing, and topography of this complex tectonic feature to understand more about the origin of coronae and how they relate to similar features on Earth. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36658 9/19/90 On September 15, 1990, the Magellan spacecraft started radar operations for its mapping mission at Venus. This image is taken from the first set of radar data collected in the normal operating mode. This Magellan radar image is part of the southern Lavinia Planitia region of Venus obtained during orbit 377. The center of the image is at 356 degrees east longitude, 68.7 degrees south latitude. The image is 30 kilometers (18 miles) wide and 70 kilometers (43 miles) long. On the basis of Arecibo data it is known that these features are located near the center of a large oval-shaped deformation structure, known as a corona, 775 kilometers (480 miles) in diameter adjacent to east-northeast trending linear features. The center of this corona is the focus of abundant lava flows extending hundreds of kilometers into the surrounding plains. The Magellan image reveals the details of this central volcanic source region. The Magellan image is characterized by an egg-shaped fault-bounded depression (center left of the image) interpreted to be a volcanic caldera, a radar-bright lobate deposit interpreted to be a volcanic flow, and multiple east-west trending bright linear structures interpreted to be fault scarps and troughs. Calderas form from the withdrawal of molten rock from a chamber below the surface and collapse of the overlying rocks. The egg-shaped caldera shows evidence of two stages of collapse. The outer boundary, which appears to have a slightly raised rim, is 8 x 10 kilometers (5 x 6 miles) in diameter; the inner boundary is 5 x 6 kilometers (3 x 4 miles) in diameter. The floor of the caldera is 4 x 6 kilometers (2.5 x 4 miles) in diameter and appears smooth. The part of the bright lava flow seen in this image (just south of the caldera) is 30 kilometers (18 miles) long and 2-12 kilometers (1.25-7.5 miles) wide. Various features often associated with lava flows are observed. Features resembling raised levees are observed along the edges of the flow in the western part of the image. Lobate extensions of the flow are observed in a direction towards the caldera. A variety of cross-cutting relationships of linear structures and the flow are observed. On Earth, such linear features are often the sources of flows. The linear feature north of the caldera extends across the width of the image, is approximately 2 kilometers (1.25 miles) wide, and appears to be a trough that tapers to the east. The linear features to the south of the caldera extend from 13 to at least 30 kilometers (8-18 miles) across the image and are 1-2 kilometers (.62-1.24 mile) wide. These features may represent fault scarps or troughs, and are likely associated with the movement of subsurface magma and the formation of the large corona in which these features occur. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36697 MGN-14 9/25/90 This is a Magellan image mosaic of an impact crater located in Guinevere Planitia with a rim diameter 12.5 kilometers (7.8 miles). The mosaic is located at 6 degrees north latitude , 335 degrees longitude, and is from orbits 376 and 377 obtained on September 15, 1990. The image is about 37 kilometers (23 miles) wide and 80 kilometers (48 miles) long. Material thrown out from the impact forms a bright ejecta blanket surrounding most of the crater. The object that formed this crater was probably moving toward the north (top of picture) at a shallow angle to the surface when it hit. The two lines of evidence that support this view are the "missing ejecta" on the south and the small secondary craters seen to the north. The secondary craters are formed by large blocks thrown out of the primary crater. Most of the larger blocks landed close to the crater rim, while finer material traveled farther, creating a radial pattern. The inside of the crater shows terracing caused by slumping of the inner wall. A complex central peak is also seen; it was formed by uplift of the ground when it rebounds following impact. Resolution of the Magellan data is about 120 meters (400 feet). PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CA 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION Magellan P-36698 MGN-15 9/24/90 This Magellan image shows an area 40 kilometers (25 miles) by 112 km (70 miles) to the northeast of Ushas Mons on Venus. It was obtained on September 16, 1990 when the spacecraft was on its 384th orbit of the planet. This image shows evidence of possible explosive volcanism and eolian or wind activity. The image shows two types of plains - fractured and smooth. The smooth plains in the center of the image appear to overlay the fractured plains. Extending from the one kilometer (0.6 mile) diameter crater in the middle of the image is a radar-bright fractured surface that broadens away from the crater. It is brighter near the crater and fades gradually into smooth plains at its distal end 10 kilometers (6 miles) from the crater. A similar but darker deposit extends away from the crater to the left. These streaks are interpreted to form due to the scouring away of the smooth plains deposit by the wind, revealing the fractured plains below. The smooth plains deposit and the craters may have formed by fallout from volcanic explosion plumes. Their characteristics are typical of terrestrial pyroclastic volcanic deposits. Resolution of the Magellan data is about 120 meters (400 feet). JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36699 MGN-16 9/25/90 This is a Magellan radar image mosaic of part of the Lakshmi region of Venus. The mosaic is part of revolutions 390 and 391 acquired on September 17, 1990. The image is located at 30 degrees north latitude, 333.3 degrees east longitude, and is about 37 kilometers (23 miles) wide and 80 kilometers (48 miles) long. On the basis of Pioneer Venus and Arecibo data, it is known that the region shown is located on the low rise separating Sedna Planitia and Guinevere Planitia, and just to the west of Eistla Regio. The image shows two sets of parallel lineations which intersect almost at right angles. The fainter lineations are spaced at a regular interval of about 1 kilometer and extend beyond the boundaries of the image. The width of these faint lineations is at the limit of resolution of the best Magellan images. The brighter, more dominant lineations are less regular and appear in places to begin and end where they intersect the fainter lineations. It is not yet clear whether the two sets of lineations represent faults or fractures, but in other areas outside the image, the bright lineations are associated with pit-craters and other volcanic features. This type of terrain has not been seen previously, either on Venus or the other planets. Resolution of the Magellan data is about 120 meters (400 feet). JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36700 9/25/90 This Magellan image from orbit 376 shows about two-thirds of the well- preserved impact crater Lyudmila (Russian first name). The crater is 13.7- kilometers (8.2 miles) in diameter and is located in a nearly featureless region of Lakshmi Planum in Ishtar Terra at latitude 62.2, longitude 329.8. Lyudmila, identified from Venera 15/16 images as being a possible impact crater by Soviet scientists, is shown on Magellan's high resolution images to have the rough inner and smooth outer ejecta deposits that are characteristic of impact craters observed throughout the Solar System. The outer ejecta, resembling the petals of a daisy, extends a maximum of 13.3 kilometers (8 miles), or about one crater diameter, from the crater rim. Lyudmila also has additional characteristics of impact craters, including terraced inner walls, and a central peak. The darkness of much of the crater floor indicates a smooth surface, perhaps formed by the ponding of lava flows in the crater floor. The radar-bright ejecta of the crater may indicate that the crater is relatively young or fresh. The resolution of this image is approximately 120 meters (400 feet). The spacecraft moved from the north (top) to the south, looking to the left. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36701 9/25/90 This image from Magellan's 383rd orbit of Venus shows about half of an unnamed 47 kilometers diameter (28 miles) impact crater; it is the second largest of three similar craters closely grouped in a region of radar-dark (smooth) plains between Lavinia Planitia and Guinevere Planitia. The crater, located at latitude 26.4 degrees S. and longitude 337.3 degrees, was previously seen in Earth-based radar images acquired at the Arecibo radar observatory in Puerto Rico. The crater has many characteristics typical of meteorite impact craters, including a central peak, deposits of hummocky or hilly material immediately surrounding the crater's rim, and smoother more patchy deposits that extend further from the crater rim. Some of the hummocky ejecta appears to extend for some distance along the major lobes formed by the outer ejecta. This radial distribution of the hummocky ejecta may be a consequence of the way the material was thrown from the crater and moved through the atmosphere and along the surface. The crater's central peak, and flat floor are also common to many other impact structures; the latter probably formed by the ponding of lava flows on the crater's floor. Secondary impact craters formed by far-flung ejecta, are also present near the most distal parts of the outer ejecta deposits. The radar-bright ejecta and inner wall of this crater indicate that it is fresh and not noticeably degraded. The resolution of this image is about 150 meters (450 feet); north is to the top. The Magellan radar was illuminating the surface from left to right in this image. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36702 9/25/90 This dark plains region is of a part of the Lavinia Region in the southern hemisphere at 29.1 degrees south latitude and 337 degrees east longitude. This image is of an area 45 kilometers (28 miles) wide and 77 kilometers (48 miles) long. It shows a variety of features, including volcanic domes and pits, linear fractures, and high-standing mesas bounded by steep cliffs. A bright streaky deposit at the base of the steep cliffs in the upper right indicates downslope movement of material, and possible erosion of accumulation of windblown debris. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36703 9/25/90 This Magellan image of the Lakshmi Region of Venus was taken on September 15, 1990. The image is a mosaic of orbits 376 and 377 and shows features on the surface of Venus at 36 north latitude, 330 east longitude. The image measures 41 x 77 kilometers (25 x 48 miles) and shows the dark randomly fractured plains of Sedna Planitia. The circular feature in the center of the image is a relatively flat-topped dome, 13 x 20 kilometers (8 x 12.5 miles) in diameter at the top and 28 by at least 35 kilometers (17 x 22 miles) in diameter at the base. The top of the dome is highly fractured in a radial pattern; wider troughs extend downslope on the north and southeast flanks. The fractures in the plains deflect in a circumferential pattern around the base of the dome. A similar pattern to the west of the dome indicates the presence of a second dome to the left, off the image. Since no lava flows are observed to emanate from the dome, this feature may be a failed volcano, known as a "cryptodome". Cryptodomes form on Earth when molten rock rises but is unable to break through to the surface as lava flows. The overlying rock is bowed up, possibly fracturing the surface and forming a flat-topped dome. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36704 9/25/90 This scene, which covers an area of 75 kilometers (46 miles) by 45 kilometers (28 miles), shows an area of dark volcanic lava flows overlying the brighter surrounding plains which are thought to have been formed from older flows. Some of the dark flows terminate on the narrow bright sinuous feature to the right of the image and it is assumed that they originate from eruptions at fissures located along this bright feature. The image is located at latitude 4.6 degrees North and longitude 331.8 East. The horizontal banding is a processing artifact in this photo made from the first orbit after the start of systematic mapping. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36705 9/25/90 At least a dozen volcanic domes can be seen in this 75 kilometer (46 miles) by 45 kilometer (28 miles) area on Venus located in a plains region at latitude 25.0 degrees north and longitude 330.6 degrees east. Several of them have small summit craters. Five of them also exhibit a slightly brighter area stretching south-west from the dome into the surrounding plains. It is thought that this is indicative of a local wind direction of north-east to south-west, although the mechanism responsible for the brightening is not understood. It may be due to pyroclastic material ejected from the volcano and carried downwind or to the bright area having a different surface texture due to it lying in the wind shadow of the mountain. If these bright areas are indicative of the local wind direction, then it may be possible to use them to map the global wind patterns. Steep slopes and small scale surface roughness associated with fractures are thought to be responsible for the bright lineament pattern in the plains surrounding the domes. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36706 9/25/90 This Magellan image shows a radar dark lava flow to the southeast of Navka Planitia. The image was obtained on spacecraft orbit 377 and lies on 3.5 degrees north latitude, 335 degrees longitude. Resolution of the Magellan data is about 120 meters (400 meet). This image is about 40 kilometers (24 miles) wide and about 80 kilometers (48 miles) long. The flow is over 30 kilometers (18 miles)long and 1-2 kilometers (0.6-1.2 miles) wide and appears to have been formed from relatively fluid lava. Magellan images show a wide variety of volcanic landforms indicating different styles of volcanism. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36707 9/25/90 This is a Magellan radar image of an area near the crest of the Danu Montes, a mountain range in the Lakshmi region of the planet. The area imaged is centered at latitude 58.3 degrees North, longitude 332.5 degrees. The data were taken on orbits 390 and 391 on September 17, 1990, and cover an area about 75 kilometers (45 miles) high by 30 kilometers (20 miles) wide. The dominant structures of the Danu Montes in this area are very complex ridges, troughs, and elongate blocks running from WNW to ESE. Found among these features in this image, however, are two types of collapse features, one simple and one rather complex. The simple one occurs near the top of the image, and consists of a chain of partially- coalesced pits, aligned along the dominant WNW-ESE structural trend of the region. The complex one, near the center, consists of a long, flat-floored depression that runs perpendicular to the regional trend, with two other elongate depressions that lie parallel to the trend and crosscut it. The nature of this crosscutting shows that the feature perpendicular to the regional trend formed before the ones crosscutting it. Collapse features of this sort can form as a result of withdrawal of magma from below the surface and may indicate that formation of the Danu Montes was accompanied by volcanic activity. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36708 9/25/90 This image was obtained on Sunday, September 16 by the Magellan spacecraft in orbits 383 and 384. The area is centered at 41.4 degrees south latitude, 340.4 degrees east longitude, in the Lavinia Region. The image is 40 kilometers (25 miles) wide, and 70 kilometers (43 miles) long. This region shows three NW trending, rough, bright bands spaced about 25 kilometers (15 miles) apart, each characterized by intense geologic deformation. The northernmost part of the image is the least bright of the three bright bands, with several slightly sinuous lineaments trending NW. The middle band has a much brighter concentration of straight lineaments, and some troughs ranging from 300 to 2000 meters (900-6000 feet) in width. The southern band has much more sinuous, anastomosing lineaments, which trend NW to NNW. The intervening areas are dark and smooth with only a few bright lineaments, which trend both NW and NE. This image shows two distinct scales of deformation: the bands themselves, which lie many kilometers apart, and the individual faults within the bands, which are much more closely spaced. The fine-scale deformation may indicate faulting that is concentrated very close to the surface, while the organization of the deformation into regular bands may suggest the presence of deeper layering in the crust. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36709 9/25/90 This image was obtained on Saturday, September 15 by the Magellan spacecraft in orbits 376 and 377. The area is centered at 36.4 degrees south latitude, 337.9 degrees east longitude, in the Lavinia Planitia region. The image is 37 kilometers (23 miles) wide, and 79 kilometers(48 miles) long. Narrow troughs, sinuous ridges and a broad arch are common in this area of otherwise smooth plains. The ridges and arches trend NNW and the arch is up to 5 kilometers (3 miles) wide. Most of the troughs trend WNW and are about 400-800 meters (1200-2500 feet) wide. The ridges and arch are similar to wrinkle ridges which are abundant in the lunar maria. Such wrinkle ridges consist of ridges and broad arches which formed in the smooth lava plains when the surface of the maria subsided and shortened. The similarity between wrinkle ridges and the ridges in this image suggests that this area has experienced a small amount of horizontal contraction. The small troughs may represent extension in the orthogonal direction. If the extension was contemporaneous with the compression, then a small amount of left-lateral shear oriented NW-SE is implied. 36710 JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36711 MGN-17 9/25/90 One of the most useful Magellan standard data products is the full resolution mosaic, the F-MIDR (Full-Resolution Mosaicked Image Data Record). These products are mosaics of about 500 km (300 mile) segments of 30 or more individual image strips. This is a partial F-MIDR made from orbits 376 to 399, obtained between September 15 and September 18, 1990, part of the first orbits in which the Magellan flight team operated the radar system in the mapping mode. The mosaic is centered at 27 degrees south latitude, 339 degrees longitude, in the Lavinia region of Venus. Three large impact craters with diameters ranging from 37 kilometers (23 miles) to 50 kilometers (30 miles) can be seen located in a region of fractured plains. The craters show many features typical of meteorite impact craters, including rough, radar-bright ejecta, terraced inner walls and central peaks. Numerous domes of probable volcanic origin can be seen in the southeastern corner of the mosaic. The domes range in diameter from 1-12 kilometers (0.6-7 miles), and some have central pits typical of volcanic shields or cones. Resolution of the Magellan data is about 120 meters (400 feet). 36735 JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36837 10/11/90 This Magellan image is a mosaic of data obtained during orbits 377-399. The image is 284 kilometers (176 miles) wide at the top and 250 kilometers (155 miles) wide at the bottom. It is approximately 575 kilometers (356 miles) long. The image is centered at 60 degrees south latitude and 349.6 degrees east longitude. The area shown is located within the Lavinia Region of Venus in northern Lada Terra. In the lower half of the image is an extensive system of fault scarps and graben trending NW-SE. These linear structures extend up to 300 kilometers (186 miles) in length and are 70 meters (0.04 miles) to 7 kilometers (4 miles) in width. The northern ends of the features often widen to become elongate collapse pits and calderas, 2-30 kilometers (1-18 miles) in diameter. A second set of linear features trending E-W is observed in the upper left portion of the image. The exact nature of these structures is unclear, although some appear to be graben. The formation of the linear features seen in this image may be linked to subsurface magma injection along dikes, subsequent drainage and collapse. At the intersection of these two sets of linear structures is a large quasicircular feature approximately 215-140 kilometers (135-87 miles) in diameter defined by partial arcs of semiconcentric curvilinear structures including fault scarps and graben. It is interpreted to be a corona, formed by large-scale magma upwelling from the interior of Venus. Within the corona are numerous volcanic domes and pits 2-5 kilometers (1-3 miles) in diameter, volcanic flows, and a sinuous depression approximately 47 kilometers (29 miles) long. A shield volcano 19 kilometers (12 miles) in diameter with a 1 kilometer (0.6 mile) diameter summit pit is observed near the SE boundary of the corona. The missing strip of this image is being reprocessed to remove artifacts. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36838 10/11/90 The first 3 days (24 orbits) of radar mapping from the Magellan spacecraft have revealed the presence of a wide diversity of geologic features on the surface of Venus. This full resolution mosaic centered at 20 south latitude, 337.4 east longitude is located between Navka and Lavinia Planitia and covers a region 475 kilometers (285 miles) wide and 545 kilometers (330 miles) long. Analysis of this area from lower resolution Arecibo data show that this area is part of an extensive region identified as bright plains. The Magellan data reveal the detailed geologic characteristics of different landforms in these plains. Located along the left central edge of the image is a cluster of volcanic domes which range from 1.5 kilometers to 7.5 kilometers in diameter and cover a region 150 kilometers by 100 kilometers (90 miles by 60 miles). The domes and their deposits are located at the convergence of radar-bright lineaments which are interpreted to be faults and troughs. In some places the domes overlie the faults. The faults and troughs extend into the lower part of the image where they terminate against dark plains deposits and are cross cut at right angles by additional faults. These relations indicate that multiple episodes of faulting and volcanism have occurred. An irregular shaped impact crater (11 kilometers by 8 kilometers) (7 miles by 5 miles) located in the lower left corner of the image is interpreted to have formed by multiple impacts resulting from the breakup in the atmosphere of a larger impactor. An extremely radar-dark circular region located along the right central edge of the image is interpreted as a possible region of sedimentary deposits. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36850 10/11/90 This image shows the southern extent of the elevated plateau Lakshmi Planum located in the northern high latitudes of Venus. The radar data was collected by the Magellan spacecraft between the dates September 15-18, 1990 and consists of 24 mosaicked orbit tracks. The area covered in this image is approximately 540 kilometers (335 miles) by 275 kilometers (171 miles). Lakshmi Planum proper is demarked by relatively homogeneous volcanic deposits which make up the northern two-thirds of this image. Notable features on Lakshmi include the impact crater Lyudmila (upper left portion of the image). To the east of Lyudmila are some relatively radar bright lava flows probably associated with the nearby Sacajawea caldera. Lakshmi Planum is rimmed to the south by the Danu Montes mountain belt which is seen as a radar-bright semi-circular band in the lower part of the image. Danu Montes rises approximately 450 meters (1476 feet) above Lakshmi Planum. Extension of the mountain range is expressed as northwest- southeast trending troughs or graben which appear as distinct radar-dark features in western Danu Montes. The topography drops very sharply (2.8 kilometers or 1.7 miles) south of Danu Montes. Southwest of Danu Montes is the highly fractured relatively radar-dark plains of Vesta Rupes. The southeasternmost corner of the image is another terrain known as Clotho Tessera. Tessera (from the Latin word meaning "tile") is a highly deformed type of terrain which is comprised of multiple intersecting structural trends. Interestingly, the boundary between Danu Montes, Vesta Rupes, and Clotho Tessera is marked by the presence a circular feature (located at approximately 57.9 degrees north / 333.0 degrees east) whose exact origin is unclear. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36908 MGN-24 10/25/90 This image is a mosaic of 24 Magellan orbits of Venus over the Ishtar Terra region. The image is centered at about 55 degrees north latitude and 335 degrees east longitude, and is about 300 kilometers (180 miles) across. The mosaic covers the western part of Clotho Tessera, first identified in Soviet Venera 15/16 radar images of Venus. The region is dominated by a network of intersection ridges and valleys indicating a complex history of intense deformation. Domes, pits, and smooth, dark plains regions within the tessera indicate that volcanism has also been an active process in this region. Researchers on the Magellan project are mapping this region in detail in order to unravel the styles and sequence of deformation in Clotho. Resolution of the Magellan data is approximately 120 meters (400 feet). JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-36909 10/25/90 This image is a mosaic of 24 orbits of the Navka region of Venus. The image is centered at about 10 degrees south latitude and 335 degrees east longitude. The image is about 400 km (240 miles) across. "Behepa 8" marks the approximate landing site of the Soviet Venera 8 lander, which took measurements at the surface of Venus in 1972. The Venera 8 lander measured granitic or continental-like materials at the landing site. Magellan data reveals the landing site to lie in a region of plains cut by tectonic ridges and troughs. Volcanic domes and flows are seen throughout the region. Studying the regional setting of the Venera landing sites is important in linking information about surface composition to surface morphology seen in radar images. Resolution of the Magellan data is about 120 meters (400 feet). JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37047 11/7/90 This composite image was created by inserting approximately 70 orbits of Magellan data into an image obtained at the Arecibo, Puerto Rico radiotelescope and shows a geologically complex region in the southern hemisphere of Venus. The region is centered on 65 degrees south, 359 degrees east and is about 1500 x 1500 km (900 x 900 miles) in extent. The large oval feature in the lower half of the image is Quetzalpetlatl Corona, approximately 700 km (420 miles) in diameter. Coronae are circular to oval regions defined by an annulus of ridges and are centers for tectonic and volcanic activity. Tectonic activity is largely observed in a relatively narrow rim region, which in this image is defined by a complex lineated terrain that surrounds much of the corona. Bright and dark volcanic flows are seen throughout the corona and surrounding terrain. Small shield volcanoes, 1-20 km (0.6-12 miles) in diameter, are seen near the southern limit of the Magellan data in the image. Narrow linear troughs (seen in the image as bright lines) trend to the north-northwest of Quetzalpetlatl. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37047, 1A 11/13/90 This image shows a flooded impact crater, several collapse features, and lava flows to the south of Lavinia Planitia in the southern hemisphere. Centered at 60 degrees S, 352 degrees E, the image covers an area of approximately 300 x 500 km (180 x 300 miles). The impact crater is 65 km (39 miles) in diameter and was originally about 500 meters (1300 ft) deep but has been almost completely buried by lava flows, leaving only the rim and the southeastern part of the bright, rough ejecta deposit. Recent lava flows appear as bright or dark regions with sinuous boundaries. Collapse features are linear or sinuous valleys which range from 200 meters (650 feet) to 5 km (3 miles) in width and are up to 100 km (60 miles) long. These valleys may form when subsurface magma drains along tectonic fractures, allowing the overlying surface to collapse. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37047, 2A 11/7/90 The northern rim of Quetzalpetlatl Corona is shown in this image. The region is approximately 450 km (270 miles) on a side and is centered on 64 degrees S, 359 degrees E. The rim has a hummocky, rough texture, ranges from 50 to 100 km (30 to 60 miles) in width, and rises up to 1 km (0.6 miles) above the bright lava flows to the north. In the eastern part of the image, the rim has been transected by numerous north-south trending extensional features, which are partially flooded by volcanic plains. Understanding the complex interrelationships between episodes of volcanism and tectonism will aid in unraveling the origin of coronae. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37047, 3A 11/7/90 This 60 x 100 km (36 x 60 miles) region is centered on 64 degrees S, 356 degrees E and shows lava flows that have ponded up against the rim of Quetzalpetlatl Corona. The smooth, radar bright flows partially fill a topographic trough that extends to the west and lies parallel to the rim of the corona. The flows are relatively young and appear to cover parts of both the rim of the corona and NW-SE trending fractures that lie to the north of the flow. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37047, 4A 11/7/90 The interior of Quetzalpetlatl Corona is a region of intense volcanic activity. This image is centered on 69.5 degrees S, 4 degrees E and shows a 100 x 150 km (60 x 90 mile) area containing numerous small shield volcanoes. The volcanoes range from 1-20 km (0.6-12 miles) in diameter and are strongly concentrated in an area that also contains some of the highest elevations in the corona. Bright and dark patches in the image represent flows of varying roughness, with bright regions being relatively rough and dark regions relatively smooth. Some of the volcanoes and part of the surrounding plains are dissected by valleys which appear to result from the withdrawal of subsurface magma and subsequent collapse of overlying rocks. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37125 MGN-18 11/16/90 This image of the eastern edge of Alpha Regio, 30 degrees south latitude, 11.8 east longitude, was acquired on November 7, 1990. It shows seven circular domical hills averaging 25 kilometers (15 miles) in diameter and maximum heights of 750 meters (2475 feet). These features can be interpreted as viscous or thick eruptions of lava coming from a vent on the relatively level ground allowing the lava to flow in an even lateral pattern. The concentric and radial fracture pattern on their surfaces suggests if they are extrusive that a chilled outer layer formed then further intrusion in the interior stretched the surface. The domes may be analogous to volcanic domes on Earth. An alternative interpretation is that the domes are the result of shallow intrusions up-doming the surface layers. If they are intrusive, then magma withdrawal near the end of the eruptions then produced the fractures. The bright margins possibly indicate the presence of rock debris or talus at the slopes of the domes. Fractures on the surrounding plains are both older and younger than the domical hills. Resolution of the Magellan data is about 120 meters (400 feet). JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37128 11/16/90 This Magellan image shows a complex crater, 31.9 km (20 miles) in diameter with a circular rim, terraced walls, and central peaks, located at 20.3 degrees north latitude and 331.8 degrees east longitude. Several unusual features are evidenced in this image: large dark surface up range from the crater; lobate flows emanating from crater ejecta, and very radar-bright ejecta and floor. Aurelia has been proposed to the International Astronomical Union, Subcommittee of Planetary Nomenclature as a candidate name. Aurelia is the mother of Julius Caesar. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37128 MGN-26 11/19/90 This Magellan image shows a complex crater, 31.9 kilometers (20 miles) in diameter with a circular rim, terraced walls, and central peaks, located at 20.3 degrees north latitude and 331.8 degrees east longitude. Several unusual features are evidenced in this image: large dark surface up range from the crater; lobate flows emanating from crater ejecta, and very radar- bright ejecta and floor. Aurelia has been proposed to the International Astronomical Union, Subcommittee of Planetary Nomenclature as a candidate name. Aurelia is the mother of Julius Caesar. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37129 11/20/90 This image is 50 kilometers (30 miles) across and 75 kilometers (45 miles) from top to bottom in the plains south of Clotho Tessera in the Ishtar Region. It is centered at approximately 53 degrees north, 332 degrees east. The bright and dark lineations seen throughout the image are fractures, escarpments, and graben that have resulted from the tectonic deformation that is pervasive throughout the region. These structures range in width from approximately 2 kilometers (1.2 miles) down to the limits of Magellan resolution (approximately 250 meters [825 feet]). Three large, shallow graben near the top of the image appear to have very smooth floors, and may be partially flooded by the same volcanic materials that are thought to have formed most of the plains. The dark region in the left central portion of the image is probably a region of very smooth plains, possibly a result of relatively recent volcanism. It is clearly postdated by tectonic deformation, particularly by the set of structures trending ENE and NW. The broader, diffusely bright regions adjacent to the graben may be due to mass-wasting and aeolian transport of materials from the steep scarps. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37130 11/20/90 This image is centered at approximately 29.6 degrees south latitude and 341 degrees east longitude in the Lavinia Region of Venus. Volcanic vent areas in this part of the plains west of Alpha Regio consist of domes and pits up to nearly 3 kilometers across. Extending eastward these features are sinuous channels, most of which are about 10 kilometers or more long. The channels narrow away from the pits and for most of their lengths are about 1 kilometer in diameter. The nearest planetary analogues for these features are sinuous rilles on the moon. These have been explained as lava channels and/or the result of lava erosion. On Earth lava channels form by downhill drainage of a lava flow leaving a channel behind. Lava may continue to flow in the channel once it has formed. However, lava channels on Earth are normally only a few meters or tens of meters wide. On the other hand, they may be the result of lava erosion. This is a process that only normally occurs to a limited extent on Earth because melting is inhibited by the cool upper layers of the planet. Also, lavas rarely flow turbulently enough to cause mechanical erosion. On Venus the surface materials are already at high temperatures, thus assisting thermal erosion and it is possible that lavas which may flow turbulently are more readily available than on earth. Resolution of the Magellan data is about 120 meters (400 feet). JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37131 11/20/90 This SAR image from the southern portion of Navka (24.4-25.3 degrees south latitude, 338.5-340.5 degrees east longitude) is a mosaic of twelve Magellan orbits that covers 180 kilometers (108 miles) in width and 78 kilometers (47 miles) in length. In the center of this image are two bright deposits running north to south. These deposits outline an outflow channel that flowed from a 60-km diameter crater that is to the south of the channel. Inside the outflow channel and outlined by "bathtub ring" deposits are small cones, most likely of volcanic origin. At the end of the outflow channel, where one would expect the smallest particles to be deposited, are specular features which may represent sand dunes. Seasat and space shuttle radar images of sand dunes on Earth also show specular reflections from smooth dune faces that are near-normal to the radar beam. Other evidence for aeolian activity are the dark and bright windstreaks running east to west that form behind cones. Notice how the wind changes direction from a southeast-northwest flow at the right of the image to an east-west flow at the eastern edge of the outflow channel. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37132 11/20/90 In addition to radar images of the surface, the Magellan spacecraft uses a variety of methods to study Venus and its geology. These four images of the same area show an unnamed impact crater 31 kilometers (19 miles) across in the fractured plains of Guinevere Planitia. The images are 540 by 640 kilometers (324 by 384 miles) across. These images were acquired on orbits 376 to 399 on September 15-18, 1990. They extend from 15 degrees to 25 degrees north latitude and from 315 degrees to 349 degrees east longitude. The Synthetic Aperture Radar image (upper left) shows that the crater, with its bright petal-like ejecta deposit is surrounded by a broad diffuse dark region several hundred kilometers across which is seen in other images to extend further west. This dark region is also prominent in the image at lower left which is a Reflectivity image (a measure of the strength of the radar return signal that is bounced off the surface) and shows up as a bright, highly reflective region. The radar system can also measure the RMS slope, or roughness of the surface as seen by the radar signal (image at lower right). This dark region in the radar image is also dark in the slope image, indicating it is relatively smooth. Scientists speculate that this dark region may be the result of a fine ash fallout caused by the impact explosion in the Venusian atmosphere. The volcanic fields visible at the right-hand side of the SAR image is also visible in the slope image as a rough area and is elevated (bright) in the Topography image at upper right, where brightness indicates elevation. The impact crater in the SAR image is also noticeable in the topo image as a shallow depression several hundred meters deep. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37135 11/20/90 This is a Magellan radar image mosaic of the Lavinia region of Venus. The mosaic consists of parts of orbits 376 through 416 acquired between September 15 and September 21, 1990. The center of the image is located at 40 degrees south latitude, 342.5 degrees east longitude and is about 615 kilometers (382 miles) wide and 538 kilometers (334 miles) long. The region shown includes a variety of different terrain types indicating a complex geological history. In the northern half of the image are dark mottled plains, interpreted as widespread lava flows subsequently modified by sub-parallel ridges. These are similar to the "wrinkle ridges" found on the lunar mare. To the north-west there is a cluster of volcanic edifices, the larger of which are approximately 3.5 kilometers (2.2 miles) in diameter. Some of these possess distinct summit pits and they are interpreted as lava shields. On the southern margin of the image are radar dark lava plains which also have small volcanic structures on them. Running across the southern half of the image is a large ridge belt which rises about 1 kilometer (0.6 mile) above the surrounding plains. This is interpreted to be a zone of compression and crustal thickening. In places it has been partially flooded by radar dark lavas. The relief of the individual ridges is estimated to be about 100 meters (330 ft). In places they are seen to be grouped into `bands' approximately 20 kilometers (12.4 miles) wide. The size of these bands gives a measure of the scale of deformation of the brittle upper part of the planet's crust which in turn indicates its thickness. This thickness has been calculated as approximately 4 kilometers (2.5 miles). Finally, half way down the image, towards the eastern edge, an impact crater can be seen. This crater has a diameter of about 7 kilometers (4.3 miles). Of particular note is the asymmetry of the bright ejecta material which surrounds the crater. This is one of the youngest features visible in the image. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37137 MGN-19 11/16/90 This Magellan image reveals Sacajawea Patera, a large, elongate caldera located in Western Ishtar Terra on the smooth plateau of Lakshmi Planum. The image is centered at 64.5 degrees North latitude and 337 degrees East longitude. It is approximately 420 kilometers (252 miles) wide at the base. Sacajawea is a depression approximately 1-2 kilometers (0.6-1.2 miles) deep and 120 x 215 kilometers (74 x 133 miles) in diameter; it is elongate in a southwest-northeast direction. The depression is bounded by a zone of circumferential curvilinear structures interpreted to be graben and fault scarps. These structures are spaced 0.5-4 kilometers (0.3-2.5 miles) apart, are 0.6-4.0 kilometers (0.4-2.5 miles) in width and up to 100 kilometers (62 miles) in length. Extending up to approximately 140 kilometers (87 miles) in length from the southeast of the patera is a system of linear structures thought to represent a flanking rift zone along which the lateral injection and eruption of magma may have occurred. A shield edifice 12 kilometers (7 miles) in diameter with a prominent central pit lies along the trend of one of these features. The impact crater Zlata , approximately 6 kilometers (4 miles) in diameter is located within the zone of graben to the northwest of the patera. Few flow features are observed in association with Sacajawea, possibly due to age and state of degradation of the flows. Mottled bright deposits 4-20 kilometers (2.5-12 miles) in width are located near the periphery and in the center of the patera floor within local topographic lows. Diffuse patches of dark material approximately 40 kilometers (25 miles) in width are observed southwest of the patera, superposed on portions of the surrounding graben. The formation of Sacajawea is thought to be related to the drainage and collapse of a large magma chamber. Gravitational relaxation may have caused the resultant caldera to sag, producing the numerous faults and graben that circumscribe the patera. Regions of complex, highly deformed tessera-like terrain are located north and east of the patera and are seen in the upper portion of the image. Color has been added to this image to simulate the appearance of the Venus surface. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37138 MGN-20 11/16/90 This image shows a 125 by 125 km region on the eastern flanks of Freyja Montes, in Ishtar Terra, centered on 72 degrees north, 342 degrees east. The image is dominated by a highly fractured dome, approximately 70 by 125 km (42 by 75 miles), that appears to delineate a local region of uplift and extension within the regionally compressional mountain belt. The "turtle- back" appearance of the dome is the result of two sets of intersecting fractures; one trending roughly north to north northeast and the other west to west northwest. Individual scarps appear to define graben, commonly 1 by 5 km (0.6 by 3.0 miles) wide. Age relationships between the two sets of graben are complex, but west northwest trending features most often appear to crosscut the north trending graben. In the eastern portion of the image, structures have been heavily embayed by volcanic plains deposits. The appearance of a purely extensional feature within the compressional zone of the Freyja Montes orogenic belt may have significant implications for the mechanisms by which mountains are built on Venus. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37139 MGN-21 11/16/90 This image is a full-resolution mosaic of several Magellan images and is centered at 61 degrees north latitude and 341 degrees east longitude. The image is 250 kilometers wide (150 miles). The radar smooth region in the northern part of the image is Lakshmi Planum, a high plateau region roughly 3.5 kilometers (2.2 miles) above the mean planetary radius. Lakshmi Planum is ringed by intensely deformed terrain, some of which is shown in the southern portion of the image and is called Clotho Tessera. The 64- kilometer (40 mile) diameter circular feature in the image is a depression called Siddons and may be a volcanic caldera. This view is supported by the collapsed lava tubes surrounding the feature. By carefully studying this and other surrounding images scientists hope to discover what tectonic and volcanic processes formed this complex region. The solid black parts of the image represent data gaps that may be filled in by the Magellan extended mission. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37140 MGN-22 11/16/90 This image is a mosaic of Magellan data over the Lakshmi region of Venus. The image is centered at about 66 degrees north latitude and 10 degrees east longitude. The prominent circular feature in the image is the crater Cleopatra located on the eastern slopes of Maxwell Montes, the highest mountain range on Venus. Cleopatra is about 100 km (60 miles) across and 2.5 km (1.5 miles) deep. In previous data sets, scientists were unable to determine whether Cleopatra was an impact crater or a volcanic caldera. High-resolution Magellan data indicates that Cleopatra is a double-ring impact basin, similar to double-ring impact basins identified on the Moon, Mars and Mercury. The inner and outer rings have a hummocky appearance typical of very large impact craters. On the eastern edge of Cleopatra, a flow can be seen that has breached the wall of the crater and flowed downhill to surround the ridges to the east. This flow may have been produced by melting of rocks due to the impact or by volcanism triggered by the impact. Resolution of the Magellan data is about 120 meters (400 feet). JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37141 MGN-23 11/16/90 This Magellan full resolution radar image is centered at 65 degrees north latitude, zero degrees east longitude, along the eastern edge of Lakshmi Planum and the western edge of Maxwell Montes. The plains of Lakshmi are made up of radar-dark, homogeneous, smooth lava flows. Located near the center of the image is a feature previously mapped as tessera made up of intersecting 1 to 2 km (0.6 to 1.2 miles) wide graben. The abrupt termination of dark plains against this feature indicates that it has been partially covered by lava. Additional blocks of tessera are located along the left hand edge of the image. A series of linear parallel troughs are located along the southern edge of the image. These features, 60 to 120 km (36 to 72 miles) long and 10 to 40 km (6 to 24 miles) wide are interpreted as graben. Located along the right hand part of the image is Maxwell Montes, the highest mountain on the planet, rising to an elevation of 11.5 km (7 miles) and is part of a series of mountain belts surrounding Lakshmi Planum. The western edge of Maxwell shown in this image rises sharply, 5.0 km (3.0 miles), above the adjacent plains in Lakshmi Planum. Maxwell is made up of parallel ridges 2 to 7 km (1.2 to 4.2 miles) apart and is interpreted to have formed by compressional tectonics. The image is 300 kilometers (180 miles) wide. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37236 MGN-25 12/03/90 This image shows a flooded impact crater, several collapse features, and lava flows to the south of Lavinia Planitia in the southern hemisphere. Centered at 60 degrees south latitude, 352 degrees east longitude, the image covers an area of approximately 300 x 500 kilometers (180 x 300 miles). The impact crater is 65 kilometers (39 miles) in diameter and was originally about 500 meters (1300 feet) deep but has been almost completely buried by lava flows, leaving only the rim and the southeastern part of the bright, rough ejecta deposit. Recent lava flows appear as bright or dark regions with sinuous boundaries. Collapse features are linear or sinuous valleys which range from 200 meters (650 feet) to 5 kilometers (3 miles) in width and are up to 100 kilometers (60 miles) long. These valleys may form when subsurface magma drains along tectonic fractures, allowing the overlying surface to collapse. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37264 12/5/90 This Magellan image covers a region 77 kilometers (46 miles) wide and 85 kilometers (51 miles) high. This image shows part of a long, open channel at 76.5 degrees north latitude, 335 degrees longitude in the Vires-akka Chasma, about 100 kilometers (60 miles) north of Freyja Montes, in the Denitsa Region of Venus. The channel ranges in width from less than 1 kilometer (3300 feet) to 4 kilometers (2.4 miles). The portion of the channel visible in this scene is over 120 kilometers (72 miles) long. Longitudinal scour features are visible within the channel, particularly where it makes abrupt turns. The channel may have been carved by very low viscosity lavas that were able to remain fluid over great distances and thermally erode pre-existing terrain due to the extreme temperatures at Venus' surface. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37265 12/5/90 This Magellan image is centered at 25 degrees south latitude, 345 degrees longitude, in northern Lavinia Region of Venus. The image, which is 500 kilometers (300 miles) in length and width, is a mosaic of orbits 401-437. A large impact crater with a diameter of about 40 kilometers (24 miles) has two associated lava flows at the crater's southern rim. The lava flows may have formed right after the impact. The bright radar return indicates that the flows are very rough on the scale of the radar wavelength (12 centimeters). Surrounding the crater is a dark parabolic feature that may be debris associated with the impact. The abundance of windstreaks in the image indicates that there is sediment in this area transportable by the surface winds. The windstreaks on the dark parabolic feature indicate that the wind is blowing from the southwest to the northeast at the bottom of the image and is deflected to a southeast-northwest flow around the crater. The majority of the windstreaks in this flow regime are radar bright streaks overlying radar dark streaks. To the southwest of the crater, some thin dark windstreaks flow through a ridge belt (bright linear features), apparently following the topography. At the upper left of the image is a long sinuous channel. The channel may have formed by drainage of lava to the south or it may be the result of lava erosion. Resolution of the Magellan data is about 120 meters (400 feet). JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37265 MGN-27 1/25/91 This Magellan image is centered at 25 degrees south latitude, 345 degrees longitude, in northern Lavinia Region of Venus. The image, which is 500 kilometers (300 miles) in length and width, is a mosaic of orbits 401-437. A large impact crater with a diameter of about 40 kilometers (24 miles) has two associated lava flows at the crater's southern rim. The lava flows may have formed right after the impact. The bright radar return indicates that the flows are very rough on the scale of the radar wavelength (12 centimeters). Surrounding the crater is a dark parabolic feature that may be debris associated with the impact. The abundance of windstreaks in the image indicates that there is sediment in this area transportable by the surface winds. The windstreaks on the dark parabolic feature indicate that the wind is blowing from the southwest to the northeast at the bottom of the image and is deflected to a southeast-northwest flow around the crater. The majority of the windstreaks in this flow regime are radar bright streaks overlying radar dark streaks. To the southwest of the crater, some thin dark windstreaks flow through a ridge belt (bright linear features), apparently following the topography. At the upper left of the image is a long sinuous channel. The channel may have formed by drainage of lava to the south or it may be the result of lava erosion. Resolution of the Magellan data is about 120 meters (400 feet). JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37266 12/5/90 This image is a mosaic of Magellan orbits 385-399. It covers a region 370 kilometers (220 miles) wide and 455 kilometers (270 miles) high, centered at about 30 degrees north latitude, 335 south longitude, in southeast Guinevere Planitia in the Navka Region of Venus. Trending from lower right toward upper left of the image is a long, sinuous, radar-dark rille-like feature. This rille is about 500 kilometers (300 miles) long in this image, and it has been traced for approximately an additional 500 kilometers to the east where its source may lie buried beneath younger plains volcanics. The rille maintains a nearly constant width of between 750 meters (230 feet) and 2 kilometers (1.2 miles) throughout its length. It appears to terminate in the broad, radar-dark V-shaped plains unit at the upper left. The margins of the rille are bright in the radar, suggesting levees similar to terrestrial lava channel levees. In addition, a number of faint, apparently abandoned rilles branch off the main rille, suggesting that flow was maintained for a relatively long time. Its great dimensions and implied longevity are likely due to the ability of lava in Venus' high temperature environment to remain fluid and thermally erode terrain over great distances when compared to terrestrial lava flows. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37296 12/14/90 Dark Halos Revealed Around Impact Craters: New Geologic Clocks for Venus? This Magellan image mosaic located in the Lavinia region shows the crater Carson, a 38 km (23 mile) diameter crater. The image is centered at about 24 degrees south latitude, 344 degrees longitude. Impact craters in the Magellan data are frequently surrounded by radar-dark halos. Several of these halos were noted to have a hyperbolic shape, extending hundreds of kilometers to the west of the craters. Five of these dark halos were also seen extending out from craters in Magellan emissivity data. Magellan emissivity data, derived from the altimeter data, provides information about the porosity (soil versus solid rock) and the composition of the surface. The darkness in the emissivity data indicates a very smooth surface, leading to the interpretation that these halos may be thick, smooth sediment deposits formed by the 'crushing' blow of the atmosphere associated with the incoming projectile that formed the impact crater. But why are only about 5% of the craters surrounded by these halos? On the surface of most planets, the population of impact craters can be used to obtain both relative and absolute surface ages. On Venus, as on Earth, there are relatively few craters, making relative age dating (comparing one region of the planet to another) statistically difficult. The number of craters on Venus indicates that the surface may be only about 400 million years old. The dark halos may indicate the very youngest craters on the planet - where the harsh conditions on Venus have not yet caused these dark halos to 'roughen up' and disappear. The halos could possibly be used as 'geologic clocks.' Volcanic flows or tectonic structures cutting one of these halos are interpreted to have occurred even more recently than the craters. This image shows such a situation, where flows associated with the crater cut across the halo, indicating a very young age. Scientists are continuing to identify these halos in the Magellan data, and use them to understand the geologic evolution of the surface. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37322 1/11/91 This mosaic of a portion of Alpha Regio in the Lavinia region of Venus is centered around 24.2 degrees south latitude and 1.7 degrees east longitude and covers an area about 170 kilometers (106.3 miles) by 210 kilometers (131.3 miles). The terrain shows intense folding, faulting, shearing, compression and extension. The complex pattern of intersecting ridges and valleys is called "tessera." Here, the terrain shows relatively long (50- kilometer or 30-mile) zones that intersect shorter ridges and valleys at approximately right angles. It appears that the region has undergone many episodes of horizontal motion. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37342 12/21/90 This false-color view of the volcano Sif Mons was made by superposing Magellan radar image data on altimetry data. The volcano is 2.0 kilometers (1.2 mile) high and 300 kilometers (180 miles) in diameter. Sif Mons is located on the broad 2300 kilometers x 2000 kilometers (1380 x 1200 miles) rise of Western Eistla Regio, a region that may have formed from the upwelling of hot material from the interior of the planet. The view of the mountain is from the northeast to the southwest and shows an area just below the summit of the peak. A series of bright and dark lava flows are present in the central part of the image. The brightest flows, which are relatively rough or blocky, are associated with the most recent volcanism on this part of the volcano and are superposed on darker, smoother, and older flows. The bright flows extend for a distance of 120 kilometers (72 miles) down the flank of the mountain. The long length of the flows indicates that the lavas were extremely fluid at the time that they were erupted onto the surface. The superposition of the image and topography data facilitates in identifying regions where lava flows are controlled by local changes in topography, and thus allows scientists to understand better the volcanic processes that formed the volcano and make detailed comparisons to volcanoes on Earth. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37342 MGN-28 1/25/91 This false-color view of the volcano Sif Mons was made by superposing Magellan radar image data on altimetry data. The volcano is 2.0 kilometers (1.2 mile) high and 300 kilometers (180 miles) in diameter. Sif Mons is located on the broad 2300 kilometers x 2000 kilometers (1380 x 1200 miles) rise of Western Eistla Regio, a region that may have formed from the upwelling of hot material from the interior of the planet. The view of the mountain is from the northeast to the southwest and shows an area just below the summit of the peak. A series of bright and dark lava flows are present in the central part of the image. The brightest flows, which are relatively rough or blocky, are associated with the most recent volcanism on this part of the volcano and are superposed on darker, smoother, and older flows. The bright flows extend for a distance of 120 kilometers (72 miles) down the flank of the mountain. The long length of the flows indicates that the lavas were extremely fluid at the time that they were erupted onto the surface. The superposition of the image and topography data facilitates in identifying regions where lava flows are controlled by local changes in topography, and thus allows scientists to understand better the volcanic processes that formed the volcano and make detailed comparisons to volcanoes on Earth. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37375 1/4/91 One of the most useful Magellan standard data products is the full resolution mosaic, the F-MIDR (Full-Resolution Mosaicked Image Data Record). These products are mosaics of about 500 kilometer (300 mile) segments of 30 or more individual image strips. This image is an F-MIDR made from orbits 376 to 407, obtained between September 15 and September 19, 1990, part of the first orbits in which the Magellan flight team operated the radar system in the mapping mode. The mosaic is centered at 27 degrees south latitude, 339 degrees longitude, in the Lavinia region of Venus. Three large impact craters with diameters ranging from 37 kilometers (23 miles) to 50 kilometers (30 miles) can be seen located in a region of fractured plains. The craters show many features typical of meteorite impact craters, including rough, radar-bright ejecta, terraced inner walls and central peaks. Numerous domes of probable volcanic origin can be seen in the southeastern corner of the mosaic. The domes range in diameter from 1-12 kilometers (0.6-7 miles), and some have central pits typical of volcanic shields or cones. Resolution of the Magellan data is about 120 meters (400 feet). JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37431 1/3/91 Perspective view of the southern boundary of Lakshmi Planum, Ishtar Terra, Venus. The southern scarp and basin province of western Ishtar Terra in the northern hemisphere of Venus is portrayed in this three-dimensional perspective view of Magellan radar image data. Western Ishtar Terra is an Australia-sized highland terrain that is a major focus of Magellan investigations. The highland is centered on a 2.5 to 4 kilometer-high (1.5 to 2.5 miles-high) plateau, Lakshmi Planum, which can be seen in the distance and to the right. Along this part of the Planum, the surface of the high plateau drops precipitously into the bounding lowlands, with slopes that exceed 5 percent over 50 kilometers (30 miles). The numerous fractures and valleys located on and adjacent to the steep outer slope of the plateau are clues to the formation of this unusually abrupt topographic drop. Along other parts of the boundary of Lakshmi are mountain ranges that rise as much as 6 kilometers (3.5 miles) above the plateau surface to over 11,000 meters (35,000 feet) above the mean elevation of the surface of Venus. One of these mountain ranges, Danu Montes, rises over 1.5 kilometers (1.0 mile) above the plateau and can be seen in the upper center of the image. Images such as this one show the relationship of geological features to topography and yield a valuable new perception of the radar data. For example, the small dome-shaped high (center left) is a volcano that is not apparent in the normal map-view display of Magellan images. Only when combined with topography in this fashion is the nature of the feature clearly evident. These perspective views also display fractures of the surface in their actual topographic setting. Understanding the relationship of topography to these fractures, which express the stresses and motions in the outer layers of the planet, helps geologists and geophysicists to formulate and test models for the formation of western Ishtar. The results of these studies will add to our understanding of the interior forces that shape the surface of Venus. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37431 MGN-29 1/25/91 Perspective view of the southern boundary of Lakshmi Planum, Ishtar Terra, Venus. The southern scarp and basin province of western Ishtar Terra in the northern hemisphere of Venus is portrayed in this three-dimensional perspective view of Magellan radar image data. Western Ishtar Terra is an Australia-sized highland terrain that is a major focus of Magellan investigations. The highland is centered on a 2.5 to 4 kilometer-high (1.5 to 2.5 miles-high) plateau, Lakshmi Planum, which can be seen in the distance and to the right. Along this part of the Planum, the surface of the high plateau drops precipitously into the bounding lowlands, with slopes that exceed 5 percent over 50 kilometers (30 miles). The numerous fractures and valleys located on and adjacent to the steep outer slope of the plateau are clues to the formation of this unusually abrupt topographic drop. Along other parts of the boundary of Lakshmi are mountain ranges that rise as much as 6 kilometers (3.5 miles) above the plateau surface to over 11,000 meters (35,000 feet) above the mean elevation of the surface of Venus. One of these mountain ranges, Danu Montes, rises over 1.5 kilometers (1.0 mile) above the plateau and can be seen in the upper center of the image. Images such as this one show the relationship of geological features to topography and yield a valuable new perception of the radar data. For example, the small dome-shaped high (center left) is a volcano that is not apparent in the normal map-view display of Magellan images. Only when combined with topography in this fashion is the nature of the feature clearly evident. These perspective views also display fractures of the surface in their actual topographic setting. Understanding the relationship of topography to these fractures, which express the stresses and motions in the outer layers of the planet, helps geologists and geophysicists to formulate and test models for the formation of western Ishtar. The results of these studies will add to our understanding of the interior forces that shape the surface of Venus. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37484 1/11/91 This image is located west of Alpha Regio at 26.5 south latitude, 340 east longitude. The image was processed using split-spectrum color processing to enhance details. The image shows an impact crater in the lower right with a channel feature extending from its ejecta in the north. The east- west trending streaks across the top of the image are believed to be formed by wind redistribution of fine dust and sand particles. The sharper details in the image are shown by varying the intensity of the color and the broad slowly varying radar reflectivity is depicted by varying the hue. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37492 1/14/91 Chaotic Tessera Terrain at Alpha Regio This chaotic terrain is located within central Alpha Regio and is called "tessera." Tessera is the Greek word for "tile" and was first used by the Soviets as a morphometric term to describe complicated terrains in Venera 15/16 radar imagery. This area lies between 25.0 and 26.5 degrees south latitude and between 359.9 and 1.4 degrees east longitude. This complicated type of terrain is often found at relatively high elevations up to 3 kilometers (9900 feet) above the surrounding plains. The largest structures are arcuate ridges and troughs that are about 10 kilometers (6.3 miles) wide and less than 70 kilometers (43.8 miles) long. The presence of multiple linear and curvilinear structures at various scales probably indicates that this area has undergone many episodes of deformation. Narrow graben, trending NW-SE, are ubiquitous in this area and cross-cut virtually all the other structures. Thus, these graben appear to represent the latest phase of deformation in the area. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37493 1/14/91 West-central edge of tessera at Alpha Regio The western edge of tessera terrain located at central Alpha Regio is shown in this figure. This area lies between 23.8 and 25.0 degrees south latitude and between 356.7 and 357.9 degrees east longitude. The north- south trending radar-bright and dark lineaments correspond to structures within broad topographic ridges and troughs that are also oriented north- south. The spacing of the broad ridges and troughs is about 10-20 kilometers (6.3-12.5 miles). The ridges and troughs are located within a local topographic low and are clearly embayed by smooth volcanic plains to the west. In general, the elevation increases toward the east. The existence of relatively undeformed plains at various levels upslope clearly indicates that volcanism postdates the latest structural deformation in this part of the tessera. East of this area, in central Alpha, the tessera terrain rises up to 3 kilometers (9900 feet) above the surrounding plains and is often intensely deformed. Tessera is the Greek word for "tile" and was first used by the Soviets as a morphometric term to describe complicated terrains in Venera 15/16 radar imagery. MAGELLAN PROJECT OFFICE P-37500 1/21/91 This is a Magellan radar image mosaic of Venus centered on 30 degrees south, 9 degrees east. This scene is approximately 600 kilometers (360 miles) across and includes data from orbits 522 through 561, acquired on October 5-10, 1990. The bright terrain unit is the southeastern portion of Alpha Regio, a mountainous, highly fractured region. The complex fracture and deformation history of Alpha Regio is responsible for the intricate pattern of ridges and valleys. To the south and east these highlands have been flooded and embayed by dark, smooth plains material which apparently formed by extensive eruptions of basalt-like lavas. Several lava flow channels are visible at bottom center. Volcanically embayed remnants of Alpha Regio can be seen as isolated patches. Within these dark plains occur eight rounded "pancake" domes up to 35 kilometers (20 miles) across and up to 1 kilometer (0.6 miles) high clustered at right center and at bottom right. Several of these domes have fractured and pitted summits. The shapes of these broad flat domes suggests they formed from the extrusion of lavas considerably more viscous (sticky) than those that formed the dark plains. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-37501 1/21/91 Arachnoids, one of the more remarkable features found on Venus, are seen on radar-dark plains in this Magellan image mosaic in the Fortuna region. The image is centered at about 40 degrees north latitude, 18 degrees longitude. As the name suggests, arachnoids are circular to ovoid features with concentric rings and a complex network of fractures extending outward. In this image, the arachnoids range in size from approximately 50 kilometers (29.9 miles) to 230 kilometers (137.7 miles) in diameter. Since arachnoids are similar in form but generally smaller than coronae (circular volcanic structures surrounded by a set of ridges and grooves as well as radial lines), one theory concerning their origin is that they are a precursor to coronae formation. The radar-bright lines extending for many kilometers may have been caused by an upwelling of magma from the interior of the planet which pushed up the surface to form "cracks." Radar-bright lava flows are present in the central part of this image, also indicative of volcanic activity in this area. Some of the fractures cut across these flows, indicating that the flows occurred before the fractures appeared; such relations between different structures provides good relative age dating of events. At present, arachnoids are found only on Venus and can now be more closely studied with the high resolution (120 meter/0.07 mile) radar imagery from Magellan. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37501 MGN-30 1/25/91 Arachnoids, one of the more remarkable features found on Venus, are seen on radar-dark plains in this Magellan image mosaic in the Fortuna region. The image is centered at about 40 degrees north latitude, 18 degrees longitude. As the name suggests, arachnoids are circular to ovoid features with concentric rings and a complex network of fractures extending outward. In this image, the arachnoids range in size from approximately 50 kilometers (29.9 miles) to 230 kilometers (137.7 miles) in diameter. Since arachnoids are similar in form but generally smaller than coronae (circular volcanic structures surrounded by a set of ridges and grooves as well as radial lines), one theory concerning their origin is that they are a precursor to coronae formation. The radar-bright lines extending for many kilometers may have been caused by an upwelling of magma from the interior of the planet which pushed up the surface to form "cracks." Radar-bright lava flows are present in the central part of this image, also indicative of volcanic activity in this area. Some of the fractures cut across these flows, indicating that the flows occurred before the fractures appeared; such relations between different structures provides good relative age dating of events. At present, arachnoids are found only on Venus and can now be more closely studied with the high resolution (120 meter/0.07 mile) radar imagery from Magellan. MAGELLAN PROJECT OFFICE P-37554 1/28/91 This full-resolution mosaicked image illustrates how the relative age of features can be determined from cross-cutting relationships. The image is part of the Fortuna region of Venus and is centered at 60 degrees north latitude and 16 degrees east longitude. The image includes an area 620 kilometers (382 miles) wide and 550 kilometers (339 miles) from north to south. This image of southwestern Fortuna tessera displays the complex deformation typical of tessera. The oldest structures are relatively short, broad ridges and valleys which generally trend north-northeast. These structures are cut by long north-south to northwest-trending dark and bright lines that appear throughout the image. These are interpreted to be extensional faults, and commonly are paired and form graben (down-dropped, flat-floored valleys) and horsts (upthrown ridges). In the western half of the image, younger lava flows fill valleys formed by both of the older sets of structures. These flows are dark in the image because they are smooth. The bright feature in the northwest corner of the image is the southeastern corner of Maxwell Montes. This area is unusually radar-bright due to composition of the surface materials. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-37598 2/5/91 This image is a mosaic of Magellan orbits 376-402. It is centered at 5 degrees south latitude, 335 degrees east longitude, in the Navka region of Venus. The image is dominated by a broad plains region with scattered small volcanic constructs and extensional graben or troughs. The radar-bright and dark patches are volcanic flows overlying, or in some cases partially buried by other plains materials. Many of these flow units contain small volcanic domes. The reason for such a wide range of radar brightness variations in these flow units is probably due to differences in surface roughness and/or compositional differences. The vertical striping in this mosaic (the so-called "venetian blind effect") was caused by a two-thirds of a second mismatch between where the radar data processing system assumed the radar antenna pattern was hitting the ground and where the radar was actually illuminating the surface. This small error was enough to cause the radar processing system to improperly process data for those orbits, resulting in the banding seen here. This timing error appears only in early orbits which were acquired before the radar instrument's behavior was fully understood. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37598 MGN-31 2/22/91 This image is a mosaic of Magellan orbits 376-402. It is centered at 5 degrees south latitude, 335 degrees east longitude, in the Navka region of Venus. The image is dominated by a broad plains region with scattered small volcanic constructs and extensional graben or troughs. The radar-bright and dark patches are volcanic flows overlying, or in some cases partially buried by other plains materials. Many of these flow units contain small volcanic domes. The reason for such a wide range of radar brightness variations in these flow units is probably due to differences in surface roughness and/or compositional differences. The vertical striping in this mosaic (the so-called "venetian blind effect") was caused by a two-thirds of a second mismatch between where the radar data processing system assumed the radar antenna pattern was hitting the ground and where the radar was actually illuminating the surface. This small error was enough to cause the radar processing system to improperly process data for those orbits, resulting in the banding seen here. This timing error appears only in early orbits which were acquired before the radar instrument's behavior was fully understood. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-37599 2/12/91 This full-resolution radar image mosaic of part of Venus is centered on 75 degrees north latitude, 332 degrees east longitude. Parts of orbits 376 through 444 are included in this area, which is 310 kilometers (190 miles) wide and 550 kilometers (339 miles)north to south. The radar-bright mountains, called Freyja Montes, are probably formed mostly as a result of compressional folding and faulting of rock units. The smooth, dark plains to the south are the northernmost extent of Lakshmi Planum, a region believed covered by extensive volcanism, although several compressional fault ridges can be seen extending southward from Freyja Montes. A sinuous lava channel is seen running along the floors of some of the valleys between the mountains belts at the top of the image, indicating that these valleys are partially flooded by lavas. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37599 MGN-32 2/22/91 This full-resolution radar image mosaic of part of Venus is centered on 75 degrees north latitude, 332 degrees east longitude. Parts of orbits 376 through 444 are included in this area, which is 310 kilometers (190 miles) wide and 550 kilometers (339 miles)north to south. The radar-bright mountains, called Freyja Montes, are probably formed mostly as a result of compressional folding and faulting of rock units. The smooth, dark plains to the south are the northernmost extent of Lakshmi Planum, a region believed covered by extensive volcanism, although several compressional fault ridges can be seen extending southward from Freyja Montes. A sinuous lava channel is seen running along the floors of some of the valleys between the mountains belts at the top of the image, indicating that these valleys are partially flooded by lavas. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 (ALSO P-37600) JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN (ALSO P-37600) P-37135 11/20/90 This is a Magellan radar image mosaic of the Lavinia region of Venus. The mosaic consists of parts of orbits 376 through 416 acquired between September 15 and September 21, 1990. The center of the image is located at 40 degrees south latitude, 342.5 degrees east longitude and is about 615 kilometers (382 miles) wide and 538 kilometers (334 miles) long. The region shown includes a variety of different terrain types indicating a complex geological history. In the northern half of the image are dark mottled plains, interpreted as widespread lava flows subsequently modified by sub-parallel ridges. These are similar to the "wrinkle ridges" found on the lunar mare. To the north-west there is a cluster of volcanic edifices, the larger of which are approximately 3.5 kilometers (2.2 miles) in diameter. Some of these possess distinct summit pits and they are interpreted as lava shields. On the southern margin of the image are radar dark lava plains which also have small volcanic structures on them. Running across the southern half of the image is a large ridge belt which rises about 1 kilometer (0.6 mile) above the surrounding plains. This is interpreted to be a zone of compression and crustal thickening. In places it has been partially flooded by radar dark lavas. The relief of the individual ridges is estimated to be about 100 meters (330 ft). In places they are seen to be grouped into `bands' approximately 20 kilometers (12.4 miles) wide. The size of these bands gives a measure of the scale of deformation of the brittle upper part of the planet's crust which in turn indicates its thickness. This thickness has been calculated as approximately 4 kilometers (2.5 miles). Finally, half way down the image, towards the eastern edge, an impact crater can be seen. This crater has a diameter of about 7 kilometers (4.3 miles). Of particular note is the asymmetry of the bright ejecta material which surrounds the crater. This is one of the youngest features visible in the image. MAGELLAN PROJECT OFFICE P-37601 2/19/91 This is a Magellan full-resolution radar mosaic of the Lavinia region of Venus. The mosaic is centered at 50 degrees south latitude, 345 degrees east longitude, and spans 540 kilometers (338 miles) north to south and 900 kilometers (563 miles) east to west. As with all Magellan images acquired thus far, the illumination of the radar is from the left-hand side of the image. This area shows a diverse set of geologic features. The bright area running from the upper right to the lower left is interpreted as part of a belt of ridges, formed by compression and thickening of the upper layers of the planet. The areas between ridges suggest flooding by radar dark (and thus presumably) smoother lavas. The varied textures of the lavas can be seen in the mottled appearance of the plains which are cut by the ridges; brighter, rougher flows are also quite common. The particularly bright flows in the lower right corner are the northern extension of Mylitta Fluctus. The bright ridges adjacent to Mylitta Fluctus at the bottom center of the image also appear to have been affected by the volcanic activity. Some of these bright features have been interpreted as down-dropped areas roughly 5 kilometers (3 miles) wide. This would imply a region of extension where the crust has been pulled apart and thus was more easily flooded by the later lava flows. The thinner fractures running from the upper left seem to end at the ridge belt in the center of this mosaic. These thinner fractures are a continuation of a pattern seen throughout much of Lavinia and suggest a pattern of compression over a very large region. At the bottom of the image, overlying the ridges, is an impact crater 10-15 kilometers (6-10 miles) in diameter. The double or overlapped crater structure and asymmetrical ejecta pattern suggests that the incoming body broke up shortly before it hit, leaving closely-spaced craters. The placement of the crater on top of the ridges implies it is younger than the ridges; in fact, the crater may be one of the youngest features in this image. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, CA 91109 JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37601 MGN-33 2/22/91 This is a Magellan full-resolution radar mosaic of the Lavinia region of Venus. The mosaic is centered at 50 degrees south latitude, 345 degrees east longitude, and spans 540 kilometers (338 miles) north to south and 900 kilometers (563 miles) east to west. As with all Magellan images acquired thus far, the illumination of the radar is from the left-hand side of the image. This area shows a diverse set of geologic features. The bright area running from the upper right to the lower left is interpreted as part of a belt of ridges, formed by compression and thickening of the upper layers of the planet. The areas between ridges suggest flooding by radar dark (and thus presumably) smoother lavas. The varied textures of the lavas can be seen in the mottled appearance of the plains which are cut by the ridges; brighter, rougher flows are also quite common. The particularly bright flows in the lower right corner are the northern extension of Mylitta Fluctus. The bright ridges adjacent to Mylitta Fluctus at the bottom center of the image also appear to have been affected by the volcanic activity. Some of these bright features have been interpreted as down-dropped areas roughly 5 kilometers (3 miles) wide. This would imply a region of extension where the crust has been pulled apart and thus was more easily flooded by the later lava flows. The thinner fractures running from the upper left seem to end at the ridge belt in the center of this mosaic. These thinner fractures are a continuation of a pattern seen throughout much of Lavinia and suggest a pattern of compression over a very large region. At the bottom of the image, overlying the ridges, is an impact crater 10-15 kilometers (6-10 miles) in diameter. The double or overlapped crater structure and asymmetrical ejecta pattern suggests that the incoming body broke up shortly before it hit, leaving closely-spaced craters. The placement of the crater on top of the ridges implies it is younger than the ridges; in fact, the crater may be one of the youngest features in this image. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-37651 2/25/91 This mosaic of Magellan data in the Fortuna region of Venus, centered at 49 degrees north latitude, 2 degrees longitude, shows two coronae. Coronae are large circular or oval structures first identified in Soviet radar images of Venus. The structure on the left, Bahet Corona, is about 230 kilometers (138 miles) long and 150 kilometers (90 miles) across. A portion of Onatah Corona, over 350 kilometers (210 miles) in diameter, can be seen on the right of the mosaic. Both features are surrounded by a ring of ridges and troughs, which in places cut more radially-oriented fractures. The centers of the features also contain radial fractures as well as volcanic domes and flows. Coronae are thought to form due to the upwelling of hot material from deep in the interior of Venus. The two coronae may have formed at the same time over a single upwelling, or may indicate movement of the upwelling or the upper layers of the planet to the west over time. A 'pancake' dome, similar to low-relief domes see in the southern hemisphere, is located just to the southwest of Bahet. Resolution of the Magellan data is about 120 meters (400 feet). Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-37706 2/19/91 The Magellan synthetic aperture radar (SAR) imaged this unique "triplet crater," or "crater field" during orbits 418-421 on 21 September 1990. These craters are 14 kilometers, 11 kilometers, and 9 kilometers in diameter, respectively, and are centered at latitude -30.1 degrees south and longitude 345.5 degrees east. The Magellan Science Team has proposed the name Stein for this crater field after the American author, Gertrude Stein. This name has not yet been approved by the International Astronomical Union. The crater field was formed on highly fractured plains. The impacts generated a considerable amount of low viscosity "flows" thought to consist largely of shock-melted target material along with fragmented debris from the crater. The three craters appear to have relatively steep walls based on the distortion in the image of the near and far walls of the craters in the Magellan radar look direction (from the left). The flow deposits from the three craters extend dominantly to the northeast (upper right). Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-37707 2/19/91 During orbits 423 through 424 on 22 September 1990, Magellan imaged this impact crater that is located at latitude 10.7 degrees north and longitude 340.7 degrees east. This crater is shown as a representative of Venusian craters that are of the proper diameter (about 15 kilometers) to be "transitional" in their morphology between "complex" and irregular" craters. Complex craters account for about 96 percent of all craters on Venus with diameters larger than about 15 kilometers; they are thought to have been formed by the impact of a large, more or less intact, mass of asteroidal material that has not been excessively effected during its passage through the dense Venusian atmosphere. Complex craters are characterized by circular rims, terraced inner wall slopes, well-developed ejecta deposits, and flat floors with a central peak or peak ring. Irregular craters make up about 60 percent of the craters with diameters less than about 15 kilometers. Irregular craters are thought to form as the result of the impact of asteroidal projectiles that have been aerodynamically crushed and fragmented during their passage through the atmosphere. Irregular craters are characterized by irregular and/or discontinuous rims and hummocky or multiple floors. The "transitional" crater shown here has a somewhat circular rim like larger complex craters, but has the hummocky floor and asymmetric ejecta characteristic of smaller irregular craters. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-37708 2/19/91 Magellan imaged this multiple-floored, irregular impact crater at latitude 16.4 degrees north, longitude 352.1 degrees east, during orbits 481 and 482 on 27 September 1990. This crater, about 9.2 kilometers in maximum diameter, was formed on what appears to be a slightly fractured, radar-dark (smooth) plains. The abundant, low viscosity flows associated with this cratering event have, however, filled local, fault-controlled troughs (called graben). These shallow graben are well portrayed on this Magellan image but would be unrecognizable but for their coincidental infilling by the radar-bright crater flows. This fortuitous enhancement by the crater flows of fault structures that are below the resolution of the Magellan synthetic aperture radar is providing the Magellan Science Team with valuable geologic information. The flow deposits from the craters are thought to consist primarily of shock melted rock and fragmented debris resulting from the nearly simultaneous impacts of two projectile fragments into the hot (800 degrees Fahrenheit) surface rocks of Venus. The presence of the various floors of this irregular crater is interpreted to be the result of crushing, fragmentation, and eventual aerodynamic dispersion of a single entry projectile during passage through the dense Venusian atmosphere. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37786 MGN-34 3/5/91 Thirty-six orbits of full-resolution data from the northern edge of central Alpha Regio are shown in this image. The image width is about 600 kilometers (375 miles). The bright lineated terrain is a series of troughs, ridges, and faults that are oriented in many directions. The lengths of these features generally range from 10 kilometers (6.3 miles) to 50 kilometers (31.3 miles). The topographic elevation within Alpha Regio varies over a range of 4 kilometers (2.5 miles). Local topographic lows, whose outlines are generally controlled by structures within the central region, are relatively radar-dark and filled with volcanic lavas. Source vents for this volcanism appear as bright spots within the smooth plains units. A distinct example of late-stage deformation of Alpha is the narrow band of southwest-northeast trending faults that disrupt older terrain between -20 degrees and -22 degrees latitude. Another interesting feature is the 35 kilometers (21.9 miles) diameter volcanic edifice located at the upper right of the image. The center of the volcano is a local topographic low and its western edge appears to be breached. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37787 MGN-35 3/5/91 This Magellan image shows part of the northern boundary of Ovda Regio, one of the large highlands ringing the equator of Venus. The scene consists largely of low-relief, rounded linear ridges. These ridges, 8-15 kilometers (5-9 miles) in width and 30-60 kilometers (20-40 miles) long, lie mostly along a 100-200 kilometer (60-120 mile) wide slope where the elevation drops 3 kilometers (2 miles) from Ovda Regio to the surrounding plains. Some of the ridges have been cut at right angles by extension fractures. Dark material, either lava or windblown dirt, fills the region between the ridges. The curvilinear, banded nature of these ridges suggests that crustal shortening, roughly oriented north-south, is largely responsible for their formation. Such crustal shortening was unexpected by Magellan scientists, who believed that Ovda Regio, a likely site of hot upwelling from the interior of Venus, should be dominated by volcanism and crustal extension. This image, centered approximately at 1 N 81 E, measures 300 kilometers (190 miles) by 225 kilometers (140 miles) and was acquired by Magellan in November 1990. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37788 MGN-36 3/5/91 This Magellan image shows part the interior of Ovda Regio, one of the large highlands ringing the equator of Venus. Several tectonic events formed this complex block-fractured terrain. An underlying fabric of ridges and valleys strikes NE-SW. These ridges are spaced 10-20 kilometers (6-12 miles) apart and may have been caused by shortening of the crust at right angles to this trend. These structures are cut by throughgoing extension fractures trending NW-SE, suggesting a later episode of NE-SW extension. Lastly, the largest valleys, particularly the 20 kilometer (12 mile)-wide one extending across the image, were filled with dark material, probably lava. The complex internal fabric of Ovda Regio attests to a long history of tectonic deformation. This image, centered approximately at 1 S 81 E, measures 225 kilometers (140 miles) by 150 kilometers (90 miles) and was acquired by Magellan in November 1990. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-37789 MGN-37 3/5/91 This Magellan image is located in the Eistla Region of Venus in the southern hemisphere and is centered at 5.5 degrees east longitude, 18 degrees south latitude. It is 122.8 kilometers (76.1 miles) across east- west and 107.5 kilometers (66.6 miles) across north-south. North is oriented towards the top of the image. Shown in the image is an unusual volcanic edifice unlike all others previously observed. It is approximately 65.6 kilometers (40.7 miles) across at the base and has a relatively flat, slightly concave summit 34.8 kilometers (21.6 miles) in diameter. The sides of the edifice are characterized by radiating ridges and valleys that impart a fluted appearance to the construct. To the west, the rim of the edifice appears to have been breached by dark lava flows that emanated from a shallow summit pit approximately 5.4 kilometers (3.3 miles) in diameter and traveled west along a channel approximately 5.4 kilometers (3.3 miles) wide and 26.8 kilometers (16.6 miles) long. A series of coalescing, collapsed pits 2-10 kilometers (1.2-6.2 miles) in diameter are located 10 kilometers (6.2 miles) west of the summit rim. The edifice and western pits are circumscribed by faint, concentric lineaments up to 70.3 kilometers (43.6 miles) in diameter. A series of north-northwest-trending graben are deflected eastwards around the edifice; the interplay of these graben and the fluted rim of the edifice produce a distinctive scalloped pattern in the image. Several north-northwest- trending lineaments cut directly across the summit region. This peculiar volcanic construct is located 25-30 kilometers (15.5-18.6 miles) north of Alpha Regio, a highly deformed region of tessera terrain. A collection of at least 6 similar volcanoes has been observed near Thetis Regio, a region of tessera within Aphrodite Terra. Thus, these unusual constructs tentatively appear to be spatially associated with regions of tessera. The implications of this spatial association on the unusual morphology of these constructs are being investigated. MAGELLAN PROJECT OFFICE P-37824 3/11/91 During orbits 404 through 414 on 19-20 September 1990, Magellan imaged a peak-ring crater that is 50 kilometers in diameter located at latitude 27.4 degrees north and longitude 337.5 degrees east the name Barton has been proposed by the Magellan Science Team for this crater, after Clara Barton, founder of the Red Cross; however, the name is tentative pending approval by the International Astronomical Union. Barton is just at the diameter size that Venus craters appear to begin to possess peak-rings instead of a single central peak or central peak complex like does 75 percent of the craters with diameters between 50 and about 15 kilometers. The floor of the crater is flat and radar-dark, indicating possible infilling by volcanic deposits sometime following the impact event. Barton's central peak ring is discontinuous and appears to have been disrupted or separated during or following the cratering process. The extremely blocky crater deposits (ejecta) surrounding Barton appears to be most extensive on the southwest to southeast (lower left to right) side of the crater. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-37831 3/11/91 These dark diffuse circular patterns imaged by the Magellan spacecraft are thought to be effects generated by the impact of asteroids or comets into Venus' dense atmosphere. The three patterns, located in Sedna Planitia (near 45N and 350E), may represent a sequence in which a) the impactor was large enough to penetrate the atmosphere largely intact and striking the surface producing a bright, rough impact crater and ejecta blanket (right); b) the impactor was slowed down and broken up with only scattered fragments striking and scarring the surface (middle); or c) the impacting body was so small that it was disrupted and slowed down by the atmosphere creating no surface impact or scar. The dark circular regions (30-60 km in diameter) surrounding these possible impact features are thought to result from enormous shock waves transmitted to the surface by the atmosphere which are strong enough to crush surface materials into fine debris which are dark (non-scattering) in the radar images. In some cases, notably the middle image, a brighter region also formed outside of the dark zone. This may be a case where the shock was only strong enough to produce coarse fractures in volcanic flows and in this case increasing the ability to scatter radar signals. These features may prove important evidence for mapping out the types of materials on the surface of the planet. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-37944 3/14/91 This mosaic of Magellan radar images covers 5 percent of the surface of Venus, approximately the size of the United States and Canada combined. It extends 5500 kilometers (3300 miles) across and 4900 kilometers (2900 miles) from top to bottom (north is towards the top), centered on 10 N latitude, 0 longitude. A total of 300 north-south image strips were used to make this mosaic which covers the equatorial regions of Venus known as Eistla Regio and Tinatin Planitia. The black stripes are missing data orbits which may be filled in the future. Scientists use large mosaics like these to study the wide variety of geologic features and understand the regional history of Venus. Numerous bright circular impact craters are scattered throughout, ranging in diameter from less than 5 kilometers (3 miles) to 80 kilometers (48 miles). Some of these are surrounded by dark halos and streaks which may be formed during the impact process. The state of California would just fit inside the large circular fault and fracture pattern at lower center, named Heng-O Corona. This feature probably formed as a result of complex motions in the interior of Venus. Sif Mons, Gula Mons, and Sappho Patera, located at upper and left center, are three large volcanoes. Numerous lava flows run down from the summits of these volcanoes. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-37945 3/14/91 This image covers much of Ovda Regio, which forms the western part of Aphrodite Terra. It covers an area about 2250 km (1386 miles) wide by 1300 km (800 miles) north to south, and ranges in latitude from 8 north to 12 south and in longitude from 62 to 90. Ovda Regio is a highland region that rises over 4 km (2.5 miles) above the surrounding plains. Magellan images show a complex surface, with several generations of structures. A pervasive fabric of irregular broad domes and ridges and associated curvilinear valleys was flooded by lava, then fractured. The circular feature surrounded by dark lava flows in the western part of the image is a caldera, or large volcanic collapse pit. Late-stage extension created long graben, or fault-bounded valleys, is best seen near the center of the image. The northern boundary of Ovda Regio is a steep, curvilinear mountain belt made up of long, narrow, rounded ridges. These ridges are similar in appearance to folded mountain belts on Earth. Several impact craters, such as the circular feature on the western margin of the image, are scattered across the area. The bright area in the southeast part of the image indicates the presence of a radar-reflective mineral such as pyrite. Most of the highland areas on Venus display a similar bright signal. Each pixel of this C2-MIDR-scale product covers an area on the surface 675 m (2215 feet) across, representing a 9x reduction in resolution compared to full-resolution data. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-37946 3/14/91 This Magellan image centered at 25 South, 82.5 longitude shows a corona located about a thousand kilometers south of Aphrodite Terra. This unnamed corona is 375 km in diameter; it flanks a north-south trending fracture zone which meets a smaller corona in the southeast corner of the image. Coronae are thought to form as a result of heat flow from the interior of the planet melting the crust. The molten material rises toward the surface, causing it to dome. As it subsequently cools off, the dome collapses. The annular ring of fractures and graben, visible in this image, along with the volcanic domes in the center are characteristic features of coronae. Other features associated with the large corona are also noteworthy. The bright rim along the northern edge of the corona may represent blocky debris which has fallen from its flank. The pancake dome on the western edge of the corona is a viscous extrusion; it is thought to be younger than the adjacent graben, since it is superposed on top of them. The coronae are found amidst lava plains. Individual flow complexes are distinguished from each other by variations in radar brightness. This suggests subsequent events which resulted in lavas of different textures (bright greys are blockier, while darker ones are smoother). The light grey blotch in the radar-dark circumferential valley on the northwestern edge of the large corona is a section of the plains, which, because of its relative height, did not get covered by the non-viscous flow. This flow was discharged from the corona through fissures. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-37947 3/14/91 This full-resolution mosaicked image is part of Ovda Regio, which forms the western part of Aphrodite Terra. The image is centered at 5 south latitude and 70 east longitude. The image includes an area 600 km (370 miles) wide and 545 km (335 miles) from north to south. Several events are recorded by the structures displayed in this image. The oldest events were the formation of irregular broad domes and ridges on the order of 20 km (12 miles) wide and of the small-scale structure on the domes and ridges. The valleys between these ridges then were flooded by dark lava flows. An extensive fracture system radial to the circular feature at the bottom of the image then cut across the older features. An impact crater 60 km (37 miles) across is also younger than the flood lava. Full-resolution images such as this are providing clues to the origin of Aphrodite Terra, and therefore important information about Venus tectonics. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-37948 3/14/91 This Magellan mosaic covers an area 1,843 kilometers wide (1145 miles) by 1,613 kilometers high (1002 miles) centered at 45 north latitude and 11 east longitude. The mosaic shows an area in Bereghinya Planitia. This area is dominated by volcanism and displays a remarkably diverse set of surface features. The most prominent geologic structures are arachnoids which range in size from 60 to 250 kilometers (37 to 155 miles). Arachnoids are believed to be of volcanic origin and are marked by concentric ridges and fractures, and frequently are found in groupings which form networks connected by fractures which are radial to the individual arachnoids. The arachnoids are concentrated in the south east corner of this mosaic. Volcanic lava flow fields can be seen associated with two of the arachnoids (39.5 N, 16 and 40 N, 8.5). A 300 kilometer (186 miles) diameter corona (large circular structure) is seen at latitude 48 North and longitude 9 East. One theory suggests that arachnoids are an early stage of corona formation. Other volcanic features are also visible within this region. Two types of domes can be found: small shields concentrated in two groups (43 N, 8.5o and 42o N, 6o); and several 'pancake' domes at 44o N latitude and 11o longitude, and latitude 44o North and longitude 7.5o East. A long sinuous channel is visible in the NE corner of the image. The channel comes out of a group of collapse features associated with a domal structure at 52o N latitude, 19o longitude and flows for 1100 kilometers (684 miles) to the south. Finally, six impact craters can be found in the mosaic, one of which has an anomalous bright interior floor (43.5o North, 19o East). This image is a once compressed mosaic which has been reduced in resolution by a factor of three (resolution: 225 meters/738 feet) from the resolution available from Magellan (resolution: 75 meters/245 feet). Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-38054 4/2/91 Centered at 22.5 degrees north, 358 degrees east, this Magellan image shows Sif and Gula Montes, two shield volcanoes thought to be analogous to volcanoes in the Hawaiian Islands. Surrounded by the relatively smooth plains of Eistla Regio, layer upon layer of flow complexes extend more than 500 kilometers (300 miles) from the shield summits into the plains. Gula Mons, the taller of the two, stands more than four kilometers above the surrounding plains. On Sif Mons flows and fractures radiate from a central peak dimpled with pit craters. A fracture zone trends NNW from Gula Mons to a low relief dome-skirted by lava flows hundreds of kilometers in length. A larger fracture zone extends past the lower right-hand corner of the image. The dark horseshoe-shaped halo around the crater in the right center and the streak in the upper center of the image are smooth surfaces thought to have formed from the interaction of the shock wave of the impacting object with the surface. Smooth areas appear dark on the image since they return fewer radio waves. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-38055 4/2/91 Multiple lava flows off the northern slope of Sif Mons, a shield volcano located approximately 22 degrees north latitude, 352 degrees east longitude, on the northwestern end of Eistla Regio are seen in this Magellan image mosaic. The image is about 600 kilometers (360 miles) across. Descending two to three kilometers (1.2-1.8 miles) into the finger-like plains, the flows form patterns which reveal the topography and some geologic features. The flows bend in the direction of the steepest slope, turning more than 90 degrees on the plains where they eventually pond. The long flow in the center flowed around small shield volcanoes but was thin enough not to cover their peaks. Radar-bright lineations associated with the long flow to the east show where lava has been diverted into troughs. The darkness around the impact crater on the lower left side of the image is characteristic of either pulverization during the initial interaction with the impacting body and the surface or the settling of particles thrown into the atmosphere after impact. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-38056 4/2/91 This is a full resolution mosaic of Magellan orbits 492-524 centered at 25 degrees north latitude, 357 east longitude in southern Sedna Planitia on Venus. The irregular circular feature or corona in the right center of the image is a low dome approximately 100 kilometers (60 miles) in diameter. The corona is flanked by two major lava flows that extend downslope to the north for several hundred kilometers. The entire region lies on the northern flank of a broad regional highland that contains the two volcanic centers of Sif Mons and Gula Mons. The dark streak in the upper left of the image is associated with a small impact crater. The object that formed the crater appears to have broken up in its passage through the dense Venusian atmosphere. The radar dark streaks associated with small impact craters may form from interaction of an intense shock wave with the surface. The radar dark surface is smoother than its surroundings. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-38088 4/5/91 This is a 225 meter per pixel Magellan radar image mosaic of Venus, centered at 47 degrees south latitude, 25 degrees east longitude in the Lada region. The scene is approximately 550 kilometers (341 miles) east- west by 630 kilometers (391 miles) north-south. The mosaic shows a system of east-trending radar-bright and dark lava flows encountering and breaching a north-trending ridge belt (left of center). Upon breaching the ridge belt, the lavas pool in a vast, radar-bright deposit (covering approximately 100,000 square kilometers [right side of image]). The source caldera for the lava flows, named Ammavaru, lies approximately 300 kilometers (186 miles) west of the scene. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38089 4/12/91 This is a 225 meter per pixel Magellan radar image mosaic of part of Venus, centered at 51 degrees south latitude, 21 degrees east longitude. The scene is approximately 200 kilometers (124 miles) east-west by 160 kilometers (99 miles) north-south. Running from west to east across the center of the image is part of a 1200 kilometer (744 miles) long by 20- kilometer (12-mile) wide lava channel in the Lada Terra region of Venus. Numerous streamlined structures within the channel attest to the very high temperature, very fluid lavas (resulting in both thermal and mechanical erosion) responsible for carving the channel. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38098 4/12/91 This Magellan radar image shows Alpha Regio, a topographic upland approximately 1300 kilometers across which is centered on 25 degrees south latitude, 4 degrees east longitude. In 1963, Alpha Regio was the first feature on Venus to be identified from earth-based radar. The radar-bright area of Alpha Regio is characterized by multiple sets of intersecting trends of structural features such as ridges, troughs and flat-floored fault valleys that together form a polygonal outline. Circular-to-oblong dark patches within the complex terrain are local topographic lows that are filled with smooth volcanic lava. Complex ridged terrains such as Alpha, formerly called "tessera" in Venera 15/16 and Arecibo radar data, appear to be a widespread and common surface expression of Venusian tectonic processes. Directly south of the complex ridged terrain is a large ovoid- shaped feature named Eve. The radar-bright spot located centrally within Eve marks the location of the prime meridian of Venus. Magellan radar data reveals that relatively young lava flows emanate from Eve and embay the southern margin of the ridged terrain at Alpha. The mosaic was produced by Eric De Jong and Myche McAuley in the JPL Multimission Image Processing Laboratory. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38101 4/5/91 This Magellan image mosaic shows the largest (275 kilometers in diameter [170 miles]) impact crater known to exist on Venus at this point in the Magellan mission. The crater is located north of Aphrodite Terra and east of Eistla Regio at latitude 12.5 degrees north and longitude 57.4 degrees east, and was imaged during Magellan orbit 804 on November 12, 1990. The Magellan science team has proposed to name this crater Mead, after Margaret Mead, the American Anthropologist (1901-1978). All Magellan-based names of features on Venus are, of course, only proposed until final approval is given by the International Astronomical Union-Commission on Planetary Nomenclature. Mead is classified as a multi-ring crater with its innermost, concentric scarp being interpreted as the rim of the original crater cavity. No inner peak-ring of mountain massifs is observed on Mead. The presence of hummocky, radar-bright crater ejecta crossing the radar-dark floor terrace and adjacent outer rim scarp suggests that the floor terrace is probably a giant rotated block that is concentric to, but lies outside of, the original crater cavity. The flat, somewhat brighter inner floor of Mead is interpreted to result from considerable infilling of the original crater cavity by impact melt and/or by volcanic lavas. To the southeast of the crater rim, emplacement of hummocky ejecta appears to have been impeded by the topography of preexisting ridges, thus suggesting a very low ground- hugging mode of deposition for this material. Radar illumination on this and all other Magellan image products is from the left to the right in the scene. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38102 4/5/91 Arachnoids, among the more remarkable features found on Venus, are seen on radar-dark plains in this Magellan image mosaic in the Fortuna region. The image is centered at about 40 degrees north latitude, 18 degrees longitude. Arachnoids are circular to ovoid features with concentric rings and a complex network of fractures extending outward. The top image is a mosaic of Magellan radar images with a resolution of 120 meters. The Magellan image is illuminated from the left at an angle of 35 degrees off vertical. The bottom image was obtained by the Soviet Venera 15/16 radar system. The Venera image has a resolution of about 1.5 kilometers (.9 mile). The bottom image is illuminated from the right side at an angle of 10 degrees off vertical. This image illustrates the importance of multiple mapping angles for some areas. Notice in the top image, the bright, irregular lava flows, just to the left of bottom center. The rough lava surface is bright at the Magellan incidence angle. The lava flows are not detected in the Venera image at the higher incidence angle which is less sensitive to roughness variations. However, the high angle Venera image reveals the topography which is not easily seen at the Magellan incidence angle. In the image, the arachnoids range in size from approximately 50 kilometers (29.9 miles) to 230 kilometers (137.7 miles) in diameter. Since arachnoids are similar in form but generally smaller than coronae (circular volcanic structures surrounded by a set of ridges and grooves as well as radial lines), one theory concerning their origin is that they are a precursor to coronae formation. The radar-bright lines extending for many kilometers may have been caused by an upwelling of magma from the interior of the planet which pushed up the surface to form "cracks." Radar-bright lava flows are present in the central part of this image, also indicative of volcanic activity in this area. Some of the fractures cut across these flows, indicating that the flows occurred before the fractures appeared; such relations between different structures provides good relative age dating of events. At present, arachnoids are found only on Venus. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38103 4/5/91 This Magellan image reveals Sacajawea Patera, a large, elongate caldera located in Western Ishtar Terra on the smooth plateau of Lakshmi Planum. The image is centered at 64.5 degrees North latitude and 337 degrees East longitude. It is approximately 420 kilometers (252 miles) wide at the base. Sacajawea is a depression approximately 1-2 kilometers (0.6-1.2 miles) deep and 120 x 215 kilometers (74 x 133 miles) in diameter; it is elongate in a southwest-northeast direction. The depression is bounded by a zone of circumferential curvilinear structures interpreted to be graben and fault scarps. These structures are spaced 0.5-4 kilometers (0.3-2.5 miles) apart, are 0.6-4.0 kilometers (0.4-2.5 miles) in width and up to 100 kilometers (62 miles) in length. Extending up to approximately 140 kilometers (87 miles) in length from the southeast of the patera is a system of linear structures thought to represent a flanking rift zone along which the lateral injection and eruption of magma may have occurred. A shield edifice 12 kilometers (7 miles) in diameter with a prominent central pit lies along the trend of one of these features. The impact crater Zlata, approximately 6 kilometers (4 miles) in diameter is located within the zone of graben to the northwest of the patera. Few flow features are observed in association with Sacajawea, possibly due to age and state of degradation of the flows. Mottled bright deposits 4-20 kilometers (2.5-12 miles) in width are located near the periphery and in the center of the patera floor within local topographic lows. Diffuse patches of dark material approximately 40 kilometers (25 miles) in width are observed southwest of the patera, superposed on portions of the surrounding graben. The formation of Sacajawea is thought to be related to the drainage and collapse of a large magma chamber. Gravitational relaxation may have caused the resultant caldera to sag, producing the numerous faults and graben that circumscribe the patera. Regions of complex, highly deformed tessera-like terrain are located north and east of the patera and are seen in the upper portion of the image. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38104 4/5/91 This is a Magellan radar image covering a 105-kilometer (63- mile) by 45- kilometer (27-mile) region near Hestia Rupes on the northwestern corner of Aphrodite Terra. The complex network of narrow (<1 kilometer) fractured in the center of the image extends for approximately 50 kilometers (31 miles). This network exhibits tributary-like branches similar to those observed in river systems on Earth. However, the angular intersections of tributaries suggest tectonic control. These features appear to be due to drainage of lava along preexisting fractures and subsequent collapse of the surface. The underlying tectonic fabric can be observed in the northeast trending ridges which predate the plains. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38139 4/19/91 This complex crater in the Navka region of Venus was mapped by Magellan on September 26-27, 1990 during orbits 459 and 460. The crater has a diameter of 22 kilometers (13.6 miles) and is located at latitude 5.75 degrees south, longitude 349.6 degrees east. It has the terraced walls, flat radar-dark floor, and central peak that are characteristic of craters classified as "complex." The central peak on its floor is unusually large. Flow-like deposits extend beyond the limits of the coarser rim deposits on its west and southwest. Like about half of the craters mapped by Magellan to date, it is surrounded by a local, radar-dark halo. Buck, the proposed name for this crater honors Pearl S. Buck, American author (1892-1973). Proposed names for all features on planetary bodies are provisional until formally adopted by the International Astronomical Union. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38140 4/19/91 This beautiful impact crater in the Lada region of Venus was mapped by Magellan on October 11, 1990 during orbits 585 through 595. It is located at latitude 30.75 degrees south, longitude 20.20 degrees east. The crater, 67 kilometers (41.5 miles) in diameter, is distinctive because unusual, feather-like flows extend from the west and northwest sides of its rim. It's radar-bright floor has unique physical and electrical properties that are presently being evaluated by members of the Magellan Science Team. The crater is classified as a "peak-ring" crater because its floor has a concentric ring of hills, or peak-ring. In this crater, the peak-ring has been somewhat disrupted and is not the nearly perfect ring seen in some other large craters mapped by Magellan. A large, radar-bright, parabola- shaped deposit (not shown here) extends west from the crater for many hundreds of kilometers. It is thought to result from the interaction of fine crater ejecta with the upper atmospheric winds that are dominant in the equatorial region. Similar west-facing deposits observed by Magellan are associated with a dozen or so other bright-floored craters in the equatorial region. Stuart, the proposed name of this crater honors Mary Stuart, Queen of Scots (1542-1587). Proposed names for all features on planetary bodies are provisional until formally adopted by the International Astronomical Union. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38141 4/19/91 This Magellan full-resolution mosaicked image shows the central and northern parts of Ovda Regio, one of the large highlands ringing the equator of Venus that make up Aphrodite Terra. The complex structures displayed in this image indicate a long history involving several tectonic events. The northern third of the image is dominated by low-relief, rounded linear ridges that trend roughly east-west. These ridges lie along a 100-200 kilometer (60-120 mile) wide slope where the elevation drops 3 kilometers (2 miles) from Ovda Regio to the surrounding plains. The ridges have been interpreted as resulting from crustal shortening (compression) oriented approximately north-south. The topographic expression of the ridges is reminiscent of that displayed by folded mountain belts on Earth. Shorter, broader ridges and valleys which form the underlying fabric in the central part of Ovda may be another manifestation of this crustal shortening. Both types of ridges are cut by through-going fractures and graben (fault-bounded valleys), indicating that an episode of northeast- southwest extension followed the compressional event. The youngest event was flooding of low-lying areas by smooth (radar-dark) lava flows. The importance of crustal shortening in the formation of the equatorial highlands was not recognized prior to production of Magellan images. Instead, scientists expected that Ovda Regio, a likely site for the upwelling of hot material from the interior of Venus, should be dominated by volcanism and crustal extension. This image, centered at 0 degrees north latitude, 82 degrees east longitude, measures approximately 535 kilometers (334 miles) by 600 kilometers (375 miles) wide and was acquired by Magellan in November 1990. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38142 4/19/91 This Magellan full-resolution mosaic shows an area in Ishtar Terra on Venus, centered at 65 degrees north latitude and 6 degrees east longitude. The prominent circular feature is Cleopatra, an impact crater, 100 kilometer (62 miles) in diameter. Cleopatra lies on the eastern slopes of Maxwell Montes, the tallest mountain range on Venus at almost 11 kilometers (6.8 miles) above the mean planetary radius. The western slopes of Maxwell Montes are very steep while the eastern slopes descend gradually. The radar-bright return throughout most of the image is present on Venus at high altitudes. This phenomenon is thought to indicate the presence of a radar reflective mineral such as pyrite which is stable at the pressure and temperature found at higher altitudes. The ridges and troughs throughout the image formed from compression of the surface. It was not determined whether Cleopatra was a volcanic or impact crater until high-resolution Magellan data were received. The rough, surrounding ejecta is visible in Magellan images, distinguishing it as a large double-ring impact basin similar to those found on other planetary bodies. Lava from impact melt or volcanism triggered by the impact breached the crater rim and filled the troughs in the upper right-hand corner of the image. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38143 4/19/91 This crater, partly flooded by volcanic lavas, was mapped by Magellan on September 20, 1990 during orbits 411 through 418. It is located in the Lavinia region of Venus at 59.5 degrees south latitude and 354.5 east longitude. It is one of the very few impact craters that has been documented by Magellan to be actually in the process of elimination by volcanic resurfacing, and with a diameter of 63 kilometers (39 miles), it is the largest of these craters. The large, trough-like depression on the southwest (lower left) side is a rille or channel through which lava once flowed. A remnant of rough radial ejecta is preserved outside the crater's southeast rim. The presence of partly lava-flooded craters, such as this, are important to our understanding of the rate of resurfacing on Venus by volcanism. Resolution of the Magellan data is about 120 meters (400 feet). Alcott, the name proposed for this crater, honors Louisa May Alcott, American author (1832-1888). Proposed names for all features on planetary bodies are provisional until formally adopted by the International Astronomical Union. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38156 5/10/91 This Magellan image, centered at 42.5 degrees south latitude, 6 degrees east longitude shows Pandora Corona. It is 350 kilometers (210 miles) in diameter and is located in Lada Terra. It lies beside a northwest- southwest trending fracture zone. Many of the radial fractures in Pandora's interior appear to connect with this fracture zone, suggesting that both features may have formed at the same time. Coronae are circular to elliptical features marked by a ring of concentric ridges, and are thought to result from heat flow from the planet's interior. As hot material rises, it weakens the upper layers of the planet and causes the surface to dome upwards. Then s the region cools, the dome begins to subside. As the upper layers rise and subside, they are subjected to stresses which crack the surface, creating both circular and radial fractures. The medium grey lobes on the southern side of Pandora's outer ring are lava flows which began in fissures, or cracks, along the outer ring. The irregularly shaped features, aligned in a radial direction, are thought to be lava collapse tubes. Molten lava can flow in long channels near the surface; when the flow stops, these structures may become unstable and collapse, creating depressions on the surface. The small crater in the northeast corner of the image is 12 kilometers (7.2 miles) in diameter. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38160 4/23/91 This Magellan image is centered at 17 degrees north latitude and 62.5 longitude in the northwestern Ovda Region of Venus. The image, which is 100 kilometers (62 miles) in width and 70 kilometers (43.4 miles) in length, is a mosaic of orbits 829-834. The image shows some spectacular wind streaks 500 kilometers (300 miles) northeast of the crater Mead. Mead is the largest impact crater known to exist on Venus with a diameter of 275 km (170 miles). The large explosion associated with the impact spread debris as much as 500 kilometers away from Mead on to the surrounding plains. The streaks in this image most likely represent debris from the impact that has been modified by surface winds. It is difficult to determine whether there are bright streaks on top of darker terrain or dark streaks on top of brighter terrain. If the streaks represent radar-bright debris then the wind is blowing from the northwest to the southeast. If the streaks are composed of radar-dark material, then the wind direction is reversed. During the second cycle, Magellan scientists will look at this area again to determine if there has been any movement of the streaks. Movement will indicate active aeolian modification on the surface of Venus. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-38169 4/19/91 This is a full resolution mosaic centered at 25 degrees north latitude, 351 east longitude. The region is approximately 160 kilometers (100 miles) across. It shows a series of complex lava flows which emerge from the northern flank of Sif Mons, a large volcano just to the south. Several of the flows occupy narrow troughs formed by long fractures. A sequence of events that can be inferred from this image is the formation of the dark background plains by eruptions of extremely fluid volcanic material, and the formation of the small shield volcanoes on the plains surface that can be seen in the upper left part of the image. Next, the region was domed upward probably by heat from the interior of Venus that ultimately caused magmas to break out from the surface near the summit regions forming the Sif volcanic structure and its associated flank eruptions which can be seen in this image. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-38170 5/10/91 This 48-kilometer-diameter "complex" crater with its radar-dark flat floor and its central peak of hills is one of the three similar craters mapped in the "crater farm area". The crater is located at latitude 26.35 degrees south, longitude 337.25 degrees east. The radar-bright ejecta deposits are nearly symmetric around the crater except for their absence in a small sector on the northwest rim (upper left side). A thin, radar-dark, flow- like deposit has emanated from the rim deposits on the south side and extends to the southwest. The narrow, radar-bright bands outlining the deposit are thought to result from the piling up and roughening of the material along its sides. Danilova, the name proposed for this crater, honors a Russian ballet dancer. Proposed names for all features on planetary bodies are provisional until formally adopted by the International Astronomical Union. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38171 4/19/91 This is a full-resolution mosaicked image centered at 24.5 degrees north, 350.5 degrees east. Located on the northern slope of Sif Mons, where elevated Eistla Regio meets Sedna Planitia (plains) this area displays a simple sequence of events. The circular features, no more than 5 kilometers (3.1 miles) in diameter are small shield volcanoes, features commonly found on the Earth. The dark background plains and the shield volcanoes both formed from the eruption of very fluid lava. Then, several layers of lava flows covered each other, each one successively brighter indicating that they become blockier in texture and more viscous (sticky) in consistency with time. The summits of the shield volcanoes protrude from the flow without being covered. After the flows were emplaced, fractures formed as the new surface expanded. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38172 5/01/91 This Magellan full-resolution image shows Maxwell Montes, and is centered at 65 degrees north latitude and 6 degrees east longitude. Maxwell is the highest mountain on Venus, rising almost 11 kilometers (6.8 miles) above mean planetary radius. The western slopes (on the left) are very steep, whereas the eastern slopes descend gradually into Fortuna Tessera. The broad ridges and valleys making up Maxwell and Fortuna suggest that the topography resulted from compression. Most of Maxwell Montes has a very bright radar return; such bright returns are common on Venus at high altitudes. This phenomenon is thought to result from the presence of a radar reflective mineral such as pyrite. Interestingly, the highest area on Maxwell is less bright than the surrounding slopes, suggesting that the phenomenon is limited to a particular elevation range. The pressure, temperature, and chemistry of the atmosphere vary with altitude; the material responsible for the bright return probably is only stable in a particular range of atmospheric conditions and therefore a particular elevation range. The prominent circular feature in eastern Maxwell is Cleopatra. Cleopatra is a double-ring impact basin about 100 kilometers (62 miles) in diameter and 2.5 kilometers (1.5 miles) deep. A steep- walled, winding channel a few kilometers wide breaks through the rough terrain surrounding the crater rim. A large amount of lava originating in Cleopatra flowed through this channel and filled valleys in Fortuna Tessera. Cleopatra is superimposed on the structures of Maxwell Montes and appears to be undeformed, indicating that Cleopatra is relatively young. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-38173 5/01/91 This image, centered at 21.5 degrees north, 359.5 degrees east is part of an F-MIDR (Full-resolution Mosaicked Image Data Record) covering Magellan orbits 492-523. This is a close look at Gula Mons, a shield volcano 4 kilometers (13100 feet) in height in northwestern Eistla Regio on Venus. This type of volcanism is similar to that of the Hawaiian islands in that it is thought have resulted from hot material rising from the interior and heating the crust. Both volcanoes formed from hot, fluid lava which erupted non-explosively. The radar-bright area consists of both the summit (circular southwestern part) and radial troughs and scarps trending to the northeast down the slope of Gula Mons. Evidence of regional expansion of the crust is expressed in this area by the radial troughs or graben and a larger scale fracture complex which trends southeast from the bottom right corner of the image. The very thin lineations which extend outward from the summit before bending southward are thought to be the surface expression of a dike system (planes of solidified molten rock within bedrock). The dikes formed between intermittent outflows of lava which descend from the summit of Gula Mons. This is apparent from the observation that some dikes cut the flows while others are covered by them. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38177 4/23/91 This Magellan image is centered at 55 degrees north latitude, 348.5 degrees longitude, in the eastern Lakshmi region of Venus. The image, which is 300 kilometers (180 miles) in width and 230 kilometers (138) miles in length, is a mosaic of orbits 458-484. The image shows a relatively flat plains region composed of many lava flows. The dark flows most likely represent smooth lava flows similar to pahoehoe flows on Earth while the brighter lava flows are rougher flows similar to aa flows on Earth. The rougher flows are brighter because the rough surface returns more energy to the radar than the smooth flows. Situated on top of the lava flows are three dark splotches. Because of the thick Venusian atmosphere, the small impactors break up before they reach the surface. Only the fragments from the broken up impactor are deposited on the surface and these fragments produce the dark splotches in this image. The splotch at the far right (east) has a crater centered in it, indicating that the impactor was not completely destroyed during its journey through the atmosphere. The dark splotches in the center and to the far left in this image each represent an impactor that was broken up into small fragments that did not penetrate the surface to produce a crater. The dark splotch at the left has been modified by the wind. A southwest-northwest wind flow has moved some of the debris making up the splotch to the northeast where it has piled up against some small ridges. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38197 5/01/91 This Magellan image is a mosaic of eight orbits. The image is centered at 17.4 degrees north latitude and 338.6 degrees longitude, in the northern Navka region of Venus. It is 125 kilometers (75 miles) in width and 100 kilometers (60 miles) in length. The image shows radar-dark linear wind streaks on top of radar-dark lava flows. The streaks indicate a southeast- northwest wind direction. The darkness of the streaks indicates that the streaks are made up of small, fine material that cannot return a strong radar signal to the Magellan spacecraft. The radar-dark lava flows that the streaks lie upon are radar-dark because they are smoother than the rougher, radar-bright lava flows to the left (west). Because the streaks are associated with lava flows, they may be composed of fine ash from the volcanic eruption that produced the lava flows. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38218 5/01/91 A portion of Western Eistla Regio is displayed in this three-dimensional perspective view of the surface of Venus. The viewpoint is located 700 kilometers (430 miles) southeast of Gula Mons at an elevation of 1.2 kilometers (0.74 miles). A rift valley, shown in the foreground, extends to the base of Gula Mons, a 3 kilometers (1.86 miles) high volcano. We are looking to the northwest with Gula Mons appearing at the right on the horizon. Gula Mons is located at approximately 22 degrees north 359 degrees east. Sif Mons, a volcano with a diameter of 300 kilometers (180 miles) and a height of 2 kilometers (1.2 miles), appears to the left of Gula Mons, in the background. Magellan Synthetic Aperture Radar data is combined with radar altimetry to develop a three-dimensional map of the surface. Ray tracing is used to generate a perspective view from this map. Simulated color and radar-clinometry are used to enhance small scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced at the JPL Multimission Image Processing Laboratory by Eric De Jong, Jeff Hall and Myche McAuley, and is a single frame from the movie released at the March 5, 1991 Press Conference. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38269 6/5/91 This Magellan image, centered at 10 degrees north latitude, 188 east longitude shows the volcano Sapas Mons located in the broad equatorial rise known as Atla Regio (8 degrees north latitude, 188 degrees east longitude). Sapas Mons is about 400 kilometers (250 miles) across and rises 1.5 kilometers (0.9 miles) above the local terrain. It is about 4.5 km above the mean planetary radius. The flanks of the volcano are composed of numerous overlapping lava flows. The dark flows on the lower right are thought to be smoother than the brighter flows near the central part of the volcano. Many of the flows appear to have erupted along the flanks of the volcano, rather than from the summit. This type of flank eruption is common on large volcanoes on the Earth, such as the Hawaiian volcanoes. The summit area consists of a pair of flat-topped mesas, whose smooth tops give a relatively dark appearance in the radar image. Also seen near the summit are groups of pits, some as large as 1 kilometer (0.6 miles) across. These are thought to have formed when underground chambers of magma were drained through other subsurface tubes, leading to a collapse at the surface. A 20-kilometer (12.5-mile) diameter impact crater northeast of the volcano is partially buried by the lava flows. Little was known about the Atla Regio rise prior to Magellan. The new data, taken in February 1991, show the region to be composed of at least five large volcanic edifices such as Sapas Mons, which are commonly linked by complex systems of fractures or rift zones. By analogy with similar features on the Earth, Atla Regio is thought to result from upwellings of large volumes of molten rock from the interior of Venus known as "hot spots." Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38281 6/19/91 This Magellan image from the Atla region of Venus shows several types of volcanic features and superimposed surface fractures. The image is approximately 350 kilometers (217 miles) across, centered at 9 degrees south latitude, 199 degrees east longitude. Lava flows emanating from circular pits or linear fissures form flower-shaped patterns in several areas. A collapse depression approximately 20 kilometer by 10 kilometer (12 by 4 mile) near the center of the image is drained by a lava channel approximately 40 kilometer (25 mile) long. Numerous surface fractures and graben (linear valleys) criss-cross the volcanic deposits in north to northeast trends. The fractures are not buried by the lavas, indicating that the tectonic activity post-dates most of the volcanic activity. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38283 6/14/91 This Magellan full-resolution image shows Jeanne crater, a 19.5 kilometer (12 mile) diameter impact crater. Jeanne crater is located at 40.0 degrees north latitude and 331.4 degrees longitude. The distinctive triangular shape of the ejecta indicates that the impacting body probably hit obliquely, traveling from southwest to northeast. The crater is surrounded by dark material of two types. The dark area on the southwest side of the crater is covered by smooth (radar-dark) lava flows which have a strongly digitate contact with surrounding brighter flows. The very dark area on the northeast side of the crater is probably covered by smooth material such as fine-grained sediment. This dark halo is asymmetric, mimicking the asymmetric shape of the ejecta blanket. The dark halo may have been caused by an atmospheric shock or pressure wave produced by the incoming body. Jeanne crater also displays several outflow lobes on the northwest side. These flow-like features may have formed by fine-grained ejecta transported by a hot, turbulent flow created by the arrival of the impacting object. Alternatively, they may have formed by flow of impact melt. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38284 6/14/91 This image of Sachs Patera on Venus is centered at 49 degrees north, 334 degrees east. Defined as a sag-caldera, Sachs is an elliptical depression 130 meters (81 feet) in depth, spanning 40 kilometers (25 miles) in width along its longest axis. The morphology implies that a chamber of molten material drained and collapsed, forming a depression surrounded by concentric scarps spaced 2-to-5 kilometers (1.2-to-3 miles) apart. The arc-shaped set of scarps, extending out to the north from the prominent ellipse, is evidence for a separate episode of withdrawal; the small lobe- shaped extension to the southwest may represent an additional event. Solidified lava flows 10-to-25 kilometers (6-to-16 miles) long, give the caldera its flower-like appearance. The flows are a lighter tone of gray in the radar data because the lava is blockier in texture and consequently returns more radar waves. Much of the lava, which was evacuated from the chamber, probably traveled to other locations underground, while some of it may have surfaced further south. This is unlike calderas on Earth, where a rim of lava builds up in the immediate vicinity of the caldera. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38285 6/14/91 This Magellan image, which is 50 kilometers (31 miles) in width and 80 kilometers (50 miles) in length, is centered at 11.9 degrees latitude, 352 degrees longitude in the eastern Navka Region of Venus. The crater, which is approximately 8 kilometers (5 miles) in diameter, displays a butterfly symmetry pattern. The ejecta pattern most likely results from an oblique impact, where the impactor came from the south and ejected material to the north. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38286 6/14/91 Crater Stephania is located at 51.3 degrees latitude, 333.3 degrees longitude in northern Sedna Planitia on Venus. With a diameter of 11 kilometers (6.8 miles) it is one of the smaller craters on Venus. Because many small meteoroids disintegrate during their passage through the dense atmosphere, there is an absence of craters smaller than 3 kilometers (1.9 miles) in diameter, and even craters smaller than 25 kilometers (15.5 miles) are relatively scarce. The apron of ejected material suggests that the impacting body made contact with the surface from an oblique angle. Upon closer observation it is possible to delineate secondary craters, impact scars from blocks ejected from the primary crater. A feature associated with this and many other Venusian craters is a radar-dark halo. Since dark radar return signifies a smooth surface, it has been hypothesized that an intense shock wave removed or pulverized previously rough surface material or that a blanket of fine material was deposited during or after the impact. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38287 6/14/91 This Magellan full-resolution mosaicked image shows an unnamed crater approximately 13 kilometer (8 mile) diameter impact crater. This crater is located at 6.0 degrees north latitude, 331.9 degrees longitude. The asymmetry of the ejecta blanket indicates that the impacting body probably hit obliquely, traveling from south to north. Debris kicked up by the impact created secondary craters to the north. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38288 6/14/91 This irregularly-shaped crater is located at 51.7 degrees south latitude, 348.3 degrees longitude, with an average diameter of about 11 kilometers (7 miles). While areas east and southwest of the crater appear to be blockier than the rest of the bright ejecta, this crater does not have the usual well-defined lobate ejecta flows. Both the crater and the associated ejecta have asymmetrical forms. Impact craters on Venus in this size range commonly display these irregular features. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38290 6/14/91 This Magellan image, which is 40 kilometers (25 miles) in width and 76 kilometers (47 miles) in length, is centered at -21.4 degrees latitude, 335.2 degrees longitude in the northern Lavinia Region of Venus. The image shows an irregular crater of approximately 14-kilometer (8.7-mile) mean diameter. The crater is actually a cluster of four separate craters that are in rim contact. The noncircular rims and multiple, hummocky floors are probably the result of the breakup and dispersion of an incoming meteoroid during passage through the dense Venusian atmosphere. After breaking up, the meteoroid fragments impacted nearly simultaneously, creating the crater cluster. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38291 6/14/91 This Magellan full-resolution mosaicked image shows an intermediate-sized volcano about 50 kilometers (31 miles) in diameter. This volcano is located in northern Lada Terra at 42.6 degrees south latitude, 27.9 degrees longitude. The volcano has a central caldera-like structure (depression) about 12 kilometers (7 miles) in diameter, surrounded by an asymmetrical ring of narrow flows that extend for 15-to-40 kilometers (9-to-25 miles). To the north and northeast, an apron of older lava flows underlies the annulus and extends up to an additional 60 kilometers (37 miles). The darker stripes within the mosaic are an artifact of the radar collection; these are individual orbits in which the spacecraft's antenna was pointing very slightly off-target. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-38292 MGN-56 7/26/91 This Magellan full-resolution mosaic, centered at 55 degrees south, 354 east shows the lava flows of Mylitta Fluctus in Lavinia Planitia (plains) on Venus. The entire flow complex spans over 800 kilometers (496 miles) from north to south and 380 kilometers (236 miles) from east to west. Individual flows range in width from less than 3 to 125 kilometers (about 2 to 78 miles). The flows originate from a 700 meter (2,300 feet) high volcano located on a possible rift zone outside the image to the south. The northern flank of the volcano is seen on the southern edge of the image and consists of a diffusely bright, fan-shaped area of relatively thin flows. The main flow field descends 1 kilometer (.62 miles) into the plains until it encounters more level ground, where individual flows pond and widen. A variety of flow features such as braided channels, levees, and roughness or texture changes within flows further our understanding of the conditions of the eruption and the nature of the lava itself. These flows are thought to have been very fluid and similar to lunar mare basalts and terrestrial flood basalts. MAGELLAN PROJECT OFFICE P-38293 7/1/91 This is a Magellan radar mosaic of the Lavinia region of Venus. The mosaic is centered at 45 degrees south latitude and 350 degrees longitude and covers a region 1840 kilometers (1100 miles) by 1600 kilometers (970 miles). This topographically low region exhibits many diverse geologic features. The dominant structures are the tectonically deformed lineament belts which appear on this image as concentrated regions of parallel bright lines. These belts, which are slightly more elevated than the surrounding plains, consist of a series of ridges thought to be formed by the compression of the upper layer of the planet. Individual ridges within a belt are a few kilometers wide and tens of kilometers long. Small (less than 20 kilometers or 12 mile diameter) circular patches in the plains, such as those located in the upper left of the image, are believed to be small volcanic shields. The bright and dark lobes in the bottom center and middle right of the image are volcanic deposits that have flowed from source regions not seen in this image. The bottom flow complex is the northern part of Mylitta Fluctus, a region of vast outpourings of lava over 800 kilometers (480 miles) long. The northern part of this flow can be seen to surround a few ridges, suggesting that the ridge belts formed before the last eruptions. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-38293 MGN-57 7/26/91 This is a Magellan radar mosaic of the Lavinia region of Venus. The mosaic is centered at 45 degrees south latitude and 350 degrees longitude and covers a region 1,840 kilometers (1,100 miles) by 1,600 kilometers (970 miles). This topographically low region exhibits many diverse geologic features. The dominant structures are the tectonically deformed lineament belts which appear on this image as concentrated regions of parallel bright lines. These belts, which are slightly more elevated than the surrounding plains, consist of a series of ridges thought to be formed by the compression of the upper layer of the planet. Individual ridges within a belt are a few kilometers wide and tens of kilometers long. Small (less than 20 kilometers or 12 mile diameter) circular patches in the plains, such as those located in the upper left of the image, are believed to be small volcanic shields. The bright and dark lobes in the bottom center and middle right of the image are volcanic deposits that have flowed from source regions not seen in this image. The bottom flow complex is the northern part of Mylitta Fluctus, a region of vast outpourings of lava over 800 kilometers (480 miles) long. The northern part of this flow can be seen to surround a few ridges, suggesting that the ridge belts formed before the last eruptions. MAGELLAN PROJECT OFFICE P-38294 8/2/91 This Magellan image of Venus is centered at 25 degrees south latitude and 3 degrees east longitude. Most of this image is of complex ridge terrain, otherwise known as tessera. Relationships between ridges and troughs may indicate a time sequence of deformation, so a series of events can be hypothesized. These clues give insight into the complex nature of tectonics in tessera areas. This image shows at least two different kinds of tessera and several examples of intratessera plains. In the upper northwest quadrant an orthogonal patterned tessera is most pronounced where ridges and troughs trend west-northwest. Spaced 20 to 50 kilometers (12 to 31 miles) apart and over 50 kilometers (31 miles) in length, these troughs and ridges commonly intersect and disrupt smaller (less than 25 kilometers [16 miles] long) north-northeast-trending structures, predominantly troughs spaced about 1 kilometer (.6 mile) apart. Another kind of tessera seen in the southwest quadrant of the image is a complex tessera. Two different scales of structures are seen. The first consists of ridges and troughs in arcuate, loop-like patterns at the spacing of 10 to 20 kilometers (6 to 12). On the spacing of 1 kilometer (.6 miles) or less, structures consist of scarps, fractures and troughs. These smaller structures tend to follow local trends set by the larger loop-like structures. Intratessera plains are the dark, smooth patches scattered throughout the tessera. The very faint small bumps are shield volcanoes that are less than 5 kilometers (3 miles) across. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38295 7/26/91 This Magellan full-resolution mosaic of Venus centered at 60.3 degrees north ,337.5 degrees east shows Danu Montes (mountains) bordering on Lakshmi Planum (plains). Rising almost two kilometers (1.25 miles) above the adjacent plains, the mountains appear as ridges and troughs, implying crustal shortening by compressional forces. The highly deformed terrain, known as tessera, is present in most of the lower right portion of the image. Deep gorges separate continuous lineaments of the folded terrain, suggesting that an episode of expansion split apart the surface proceeding the compression. The largest and most prominent chasm in the image spans a width of 20 kilometers (12.5 miles) with a length of 75 kilometers (46.88). A popular theory on the processes and history of this region suggests that after the crust bunched together under compression, it heated up, became more supple and slumped into the plains. There are also round and elongate pits; some of them have long channels extending more than 75 kilometers (46.88 miles) out into the plains. The volcanic plains of Lakshmi Planum span a maximum of 2100 kilometers (1302 miles) in length and a maximum of 1500 kilometers (930 miles) in width. Only part of the southern tip is visible in this image. The plains are relatively high and level, varying from 3 to 4 kilometers (1.86 to 2.48 miles) above mean planetary radius. The fractured plains in the lower left corner of the image are over 2.5 kilometers (1.55 miles) lower in elevation than Lakshmi Planum. In the lower right portion of the image a crater, 25 kilometers (15.5 miles) in diameter appears relatively radar bright. Another crater at the bottom of the image where the fractured plains meet the tessera is similar in size but has been highly degraded by dynamic crustal forces. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38296 7/26/91 This Magellan full-resolution mosaic of Venus, centered at 69.5 degrees north, 338 degrees east shows the southern part of Freyja Montes (mountains) descending westward into the elevated volcanic plains known as Lakshmi Planum. Ridges trending north-south are thought to be either folding of the crust or low angle thrust faults, where one part of the surface slides underneath the other causing it to bunch and buckle-up. Such features result from lateral compression of the surface. Parallel to these ridges are graben (troughs), a surface expression of lateral extension. A likely scenario for this area is that the crust bunched up and subsequently fell apart under its own weight. The fact that some of the graben cut across the ridges offers further evidence that the events occurred in that time sequence. The same tectonics on a smaller scale are thought to have been responsible for the tortoise shell appearance of the oval-shaped feature at the top right portion of the image. Its collapse may have contributed to the formation of the ridges flanking the feature. Smooth volcanic plains, which are imaged by radar as uniformly dark areas, fill in the lower elevations of the fluctuating topography. In these areas, lava has been extruded, often without an obvious vent. Wrinkles or thrust faults taper off into the vast volcanic plains of Lakshmi where remnants of fractured plains are surrounded by newer, relatively featureless plains. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38297 6/19/91 This is a Magellan radar mosaic of the Navka region of Venus. The mosaic is centered at 15 degrees north latitude and 352 degrees longitude and covers a region 1840 kilometers (1100 miles) east-west and 1600 kilometers (970 miles) north-south. The north-south black bars are regions of missing data. The southern halves of two large volcanoes are located at the top of the image. Sif Mons, at the top-center, is approximately 500 kilometers (300 miles) across and rises about 2.5 kilometers (1.5 miles) above the average elevation of the planet's surface. The 30 kilometer (18 mile) circular region (called a caldera) is the probable source of the many lobate lava flows that radiate downhill. A 10 kilometer (6 mile) diameter impact crater surrounded by a dark halo is located on the slopes of the volcano 225 kilometers (135 miles) southwest of the central caldera. To the east of Sif is Gula Mons, a 550 kilometers (330 mile) diameter volcano that is 3.5 kilometers (2.1 miles) high. The summit of Gula Mons is composed of 2 calderas joined by a belt of linear deformation. The southwestern of these 2 calderas is the bright circular region in the upper right of the image. As at Sif Mons, bright and dark flows radiate downhill from the volcano. The concentrated region of bright lines southeast of Gula is the near end of a rift zone that intersects Gula at the caldera. Many other bright linear features cross the mottled plains that surround the volcanoes. In the center of the image is a 40 kilometer (24 mile) diameter impact crater. The bright halo surrounding the crater may be a fairly thin deposit, since the fractures on the underlying plains can still be seen. These plains are probably volcanic in origin; the boundaries between different areas of plains often have a flow-like morphology. There is another smaller volcano in the lower left of the image, emphasizing that this region of Venus has been very active volcanically. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38298 6/19/91 This is a Magellan radar mosaic of the Lavinia region of Venus. The mosaic is centered at 45 degrees south latitude and 350 degrees longitude and covers a region 1840 kilometers (1100 miles) east-west and 1600 kilometers (970 miles) north-south. The north-south black bars are regions of missing data. This topographically low region exhibits many diverse geologic features. The dominant structures are the tectonically deformed lineament belts which appear on this image as concentrated regions of subparallel bright lines. These belts, which are slightly more elevated than the surrounding plains, are interpreted to be composed of a series of ridges formed by the compression of the upper layer of the planet. Individual ridges within a belt are a few kilometers wide and tens of kilometers long. The medium-gray plains surrounding these ridge belts are interpreted to be volcanic in origin. Small (less than 20 kilometer or 12 mile diameter) circular patches in the plains, such as those located in the upper left of the image, are believed to be small volcanic shields. Other signs of volcanism are evident in the bottom center and middle right of the image. These bright and dark lobes of material are volcanic deposits that have flowed downhill from source regions not seen in this image. The bottom flow complex is the northern part of Mylitta Fluctus, a region of vast outpourings of lava over 800 kilometers (480 miles) long. The northern part of this flow can be seen to surround a few ridges, suggesting that the ridge belts formed before the eruption of Mylitta. The placement of the small (10-15 kilometer or 6-8 mile diameter) double impact crater on top of the ridges just to the left of Mylitta also supports the idea that the ridge belts are some of the older features in this region. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38299 7/1/91 Centered at roughly 30 North latitude, 332 East longitude, this Magellan radar image of part of the southernmost portion of the Lakshmi region of Venus depicts an area measuring roughly 540 kilometers North-South by 440 kilometers East-West (330 x 270 miles). The area is dominated by two distinct features: narrow lineaments and small shield volcanoes. Much of the image is covered by long, narrow lineaments, indicating that this region of plains has been fractured at various scales. The dominant set of fractures extends in a bright, broad zone from the northwest corner of the image down toward the southeast. The majority of the fractures in this broad zone are less than 1 kilometer (0.6 miles) wide and less than 20 kilometers (12.5 miles) in length. These short fractures are often organized in an en echelon fashion, in which a number of short, offset fractures oriented in the same direction combine to form what look like longer, individual lineaments. Although somewhat fainter, there is a second set of fractures oriented approximately perpendicular to the bright, dominant set. In those areas where the two fracture sets combine, a gridded pattern results. In places, the lineament patterns are covered by individual small shield volcanoes, measuring less than 20 kilometers (12.5 miles) in diameter at the base, or by shield fields, regions on the order of 100 kilometers (62 miles) in diameter with a concentration of small shield volcanoes. The individual volcanoes are occasionally centered on top of a lineament, suggesting that the emplacement of small shield volcanoes is structurally controlled. Since their deposits obscure the fractures, the majority of the small shield volcanoes shown in the image are probably younger than the fractures, suggesting that the most recent stage in the region's geologic development involved active surface volcanism. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38300 7/16/91 This Magellan image is centered about 24 degrees north latitude and 334 degrees longitude, in the southern Lakshmi Region of Venus. The image, 600 kilometers (372 miles) in length and 450 kilometers (279 miles) in width, is a mosaic of 24 orbits. The image shows plains that have been fractured in all directions to produce a pattern similar to an alligator's skin. Several large ridges have bright edges, particularly on their southern sides. This may be the result of wind depositing debris at the ridges' southern edge. There are two types of wind streaks associated with small volcanic cones. The first type of streak occurs in the upper left of the image. These radar-bright streaks probably represent depositional material covering the underlying plains. The streaks indicate a northeast-southwest wind flow. The second type of streak is found in the lower left side of the image. These radar-bright streaks are regions of non-deposition or scouring. The underlying plains can be seen in the streak but not in the surrounding area. The streak's fan shape indicates that the wind direction varies over several degrees, with a dominant flow towards the south. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38301 7/16/91 This Magellan full resolution mosaic shows a volcanic plains region in southern Guinevere Planitia, a lowland area 560 kilometers (347 miles) by 540 kilometers (335 miles). Multiple stages of volcanic activity have produced overlapping bright (rough-surfaced) and dark (smooth) lava flows which are especially prominent in the upper left and lower right portions of the image. Lavas can be seen as small circular flows surrounding individual volcanic cones or as extensive flows that have erupted from volcanic vents and flooded the surrounding terrain. Sets of bright thin linear bands that both cut across and are flooded by individual flows are found in the plains. A long sinuous trail of bright volcanic cones and their associated deposits extends southward from the top center of the image. Portions of this region show cracks and rifts that have been flooded by lavas from the cones and surrounding plains. Near the bottom center of the image a dark region of numerous lava flows and volcanic cones occurs among broader and more sinuous ridges and troughs. This may be a local zone of crustal extension from which rifts in the crust have allowed lavas to erupt and flood the area. The upper right corner of the image shows a portion of a 500 kilometer (310 mile) long sinuous channel through which lavas once flowed. The meandering nature of the channel suggests that the lavas were very fluid and not as viscous as lavas on Earth. Sections of the channel also appear to have been obscured by later volcanic flooding. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38302 7/16/91 This Magellan full resolution mosaic shows a volcanic plains region in southern Guinevere Planitia, a lowland area on Venus. The image, centered at 5 degrees south latitude and 334.8 degrees east longitude, covers an area 490 kilometers (304 miles) by 540 kilometers (335 miles). Multiple stages of volcanic activity have produced overlapping bright (rough- textured surface) and dark (smooth surface) lava flows which surround individual volcanic cones and flood older sections of higher ridge and trough terrain. Volcanoes, 10-20 kilometers (6-12 miles) across, are shown in the lower left of the image and are probably composed of more viscous (sticky) lavas than those flooding the plains. These structures often have a central cavity or caldera at their summits (similar to those seen, for example, in the Hawaiian islands or on the large Martian volcanoes) which may have formed as magmas feeding the volcano at depth receded into the crust. The long thin bright bands in the lower left of the image have formed from stress within the crust. They cut through one of the volcanoes and, in turn, are covered by flows from another volcano. The heart-shaped feature to the lower right of that feature is an irregular 15 kilometer (9 mile) wide impact crater showing a dark floor and bright ejecta deposits on its western and northern flanks. Impact craters such as this result from the break-up of meteoroids in the thick Venus atmosphere followed by multiple impacts from the fragments within a relatively small area. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38302 7/1/91 This image is a mosaic of Magellan orbits 376-402. It is centered at 5 degrees south latitude, 335 degrees east longitude, in the Navka region of Venus. The image is dominated by a broad plains region with scattered small volcanic constructs and extensional graben or troughs. The radar-bright and dark patches are volcanic flows overlying, or in some cases partially buried by other plains materials. Many of these flow units contain small volcanic domes. The reason for such a wide range of radar brightness variations in these flow units is probably due to differences in surface roughness and/or compositional differences. The vertical striping in this mosaic (the so-called "venetian blind effect") was caused by a two-thirds of a second mismatch between where the radar data processing system assumed the radar antenna pattern was hitting the ground and where the radar was actually illuminating the surface. This small error was enough to cause the radar processing system to improperly process data for those orbits, resulting in the banding seen here. This timing error appears only in early orbits which were acquired before the radar instrument's behavior was fully understood. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38303 7/16/91 This Magellan mosaic shows a portion of the Lada Terra highlands on Venus. The image, centered near 65 degrees south latitude and 14 degrees east longitude, covers an area about 1900 kilometers (1178 miles) north to south by about 600 kilometers (372 miles) east to west. The large complex bright terrain trending from the lower left to the upper right of the image is tessera terrain, characterized by multiple sets of complexly intersecting ridges and troughs. This region of tessera has been heavily disrupted by crustal stresses and degraded by later lava flows. The dark smooth valleys extending to the northeast area about 15-50 kilometers (9-31 miles) across and have been filled by lavas. Near the center of the image within the tessera are two small semi-circular depressions, separated by about 300 kilometers (186 miles), that may be ancient impact craters heavily modified by subsequent tessera disruption. To the north and south of the tessera lava flows have formed extensive plains regions, flooding the lower elevations of the edges of Lada Terra. At the top of the image is the southern rim of Eithinoha corona, a 500 kilometer (310 mile wide circular structure surrounded by concentric ridges thought to have formed as hot magma within the Venus crust migrated toward the surface, bowing up the crust and producing a smooth interior flooded by volcanic deposits and a ridged boundary. Large cracks or rifts are seen extending around the western edge of the corona and to the south, probably a direct result of the crustal stresses associated with the formation of the corona. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38304 7/26/91 This Magellan full-resolution image of Venus, centered at 35.5 degrees north, 332 degrees east shows an area in Sedna Planitia with a variety of morphologies. The plains have a slightly mottled appearance, indicating differences in texture, since radar return is dependent on surface roughness. The abundant white streaks present in all but the uppermost part of the image are fractures trending northwest-southeast and south southwest, bending to the northeast. Toward the bottom of the image fractures widen into deep set graben (troughs). The fractures trending northwest-southeast cross cut the southwest-northeast fractures implying that they formed more recently. The features in the center of the image with the dappled appearance are a field of shield volcanoes, with diameters from less than 1 kilometer (.62 miles) to 5 kilometers (3.1 miles). Shield volcanos typically have shallow slopes since they are formed from very fluid lava. The fact that there are few fractures present in the shield complex suggests that shields formed subsequent to the episodes of fracturing. The rough, bright grey areas along the eastern edge of the image are intricately deformed terrain called tessera. The flat-topped edifice with the star-shaped fracture pattern is a volcanic feature unique to Venus, although there are relatively few of them. These edifices, referred to as "ticks", are distinguished from others by the small ridges on their slopes radiating outward. The central part of the edifice is thought to result from magma rising toward the surface, pushing it upward. A number of mechanisms have been proposed to explain the existence of subordinate ridges. One theory is that they formed from magma reaching toward the surface along linear weaknesses. The concentric fractures around the edifice may have formed from the withdrawal of magma under the surface and the resulting collapse. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38335 5/23/91 This Magellan full-resolution mosaic of Venus centered at 60.3 degrees north, 337.5 degrees east shows the northeast portion of Danu Montes (mountains) where it borders on Lakshmi Planum (plains). Rising almost two kilometers (1.2 miles) above the adjacent plains, the mountains appear as ridges and troughs, implying crustal shortening by compressional forces. The deep gorges and valleys separate continuous ridges of the folded terrain, suggesting that an episode of expansion split apart the surface following the compression. The largest and most prominent chasm in the image spans a width of 20 kilometers (12.4 miles) with a length of 75 kilometers (46.5). There are also round and elongate pits which are thought to be areas where the surface has collapsed - perhaps where magma (subsurface molten rock) was emplaced close to the surface. In some instances lava flows from these depressions into channels extending more than 75 kilometers (46.5 miles) out onto the plains. A possible theory on the history of this region suggests that after the crust came together under compression, it heated up, became weaker, and slumped into the plains. Some evidence for this can be drawn from analogies on Earth such as the Himalayas where gravity has forced mountains to split apart under their own weight. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-38338 MGN-46 5/21/91 This image is a composite of 30 orbits recorded by the Magellan spacecraft in April 1991 superimposed on Pioneer Venus topography (the small grey triangular wedge in the upper right hand corner of the image). This image, with a resolution of 120 meters (370 feet), is centered on the equator at 288 degrees east longitude and shows the complex deformation associated with faulting in Devana Chasma. These faults have a relatively uniform spacing of approximately 5 kilometers (3 miles) and are part of 100 to 180 kilometer (60 to 108 miles) wide zone of deformation. A group of bright (rough) lava flows 70 kilometers by 280 kilometers (42 by 168 miles) flow down the raised west flanks of the Devana Chasma rift valley. The new Magellan data reveal remarkable detail and complexity in this deformed terrain. Analysis of images from areas such as Devana Chasma is expected to improve our understanding of the global tectonic forces affecting Venus. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-38339 MGN-47 5/21/91 This image is a composite of the first two orbits recorded by the Magellan spacecraft in August 1990 during the initial in-orbit test of the radar system. The data, which are superimposed on Pioneer Venus topography, are located at the intersection of Devana Chasma and the Phoebe Regio upland. The image covers a region approximately 525 kilometers by 525 kilometers (315 x 315 miles), centered at the equator and 288 degrees east longitude. It includes part of the 150 kilometer (90 miles) wide, 1.0 to 1.5 kilometer (0.6 to 0.9 miles) deep valley, Devana Chasma. Devana Chasma consists of radar bright lineaments, interpreted to be fault scarps, oriented in a north-northeast direction. This part of the planet is thought to be an area where the crust is being stretched and pulled apart producing a rift valley, similar to the East African rift. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-38340 MGN-48 5/21/91 This Magellan radar image shows a region approximately 300 kilometers (180 miles) across, centered on 59 degrees south latitude, 164 degrees east longitude and located in a vast plain to the south of Aphrodite Terra. The data for this image were obtained in January 1991. The large circular structure near the center of the image is a corona, approximately 200 kilometers (120 miles) in diameter and provisionally named Aine Corona. Just north of Aine Corona is one of the flat-topped volcanic constructs known as "pancake" domes for their shape and flap-jack appearance. This pancake dome is about 35 kilometer (21 miles) in diameter and is thought to have formed by the eruption of an extremely viscous lava. Another pancake dome is located inside the western part of the annulus of the corona fractures. Complex fracture patterns like the one in the upper right of the image are often observed in association with coronae and various volcanic features. They are thought to form because magma beneath the surface follows pre-existing fracture patterns. When eruptions or other movements of the magma occur, the magma drains from the fractures and the overlying surface rock collapses. Other volcanic features associated with Aine Corona include a set of small domes, each less than 10 kilometers (6 miles) across, located along the southern portion of the annulus of fractures, and a smooth, flat region in the center of the corona, probably a relatively young lava flow. The range of volcanic features associated with coronae suggests that volcanism plays a significant role in the formation of coronae. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-38341 MGN-49 5/21/91 This image compares the best available views of the crater Golubkina as of August 1990 (left) and April 1991 (right). The crater, 34 kilometers (21.1 miles) in diameter, is named for the Russian sculptress Anna Golubkina (1864-1927). It is located at about 60.5 degrees north latitude, 287.2 degrees east longitude. The area shown is approximately 100 kilometers (62 miles) by 215 kilometers (133 miles). The left image shows Magellan data from the initial test of the radar system (August 1990), overlain on an image obtained by the Soviet Venera 15 and 16 spacecraft in 1983-84. The data in the right image were obtained by Magellan in April 1991. The new image demonstrates the increase in detail obtained by Magellan as compared with Venera. Magellan achieved a ten-fold improvement in resolution - 120 meters (400 feet) versus 1.5 kilometers (0.9 miles), for Venera 15 and 16. The new Magellan data provide the first opportunity to "revisit" areas previously imaged by the spacecraft. There is no evidence in these images for changes in the surface over 243 days. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-38346AC April 12, 1991 This Magellan image shows two large shield volcanoes, Sif (left) and Gula (right) Montes which are located in the Eistla Region of Venus. The superimposed colors represent the planetary topography, or radius, measured from the center of the planet in kilometers. The 10-degree grid spacing is equivalent to approximately 1,050 kilometers (651 miles). Both volcanoes are thought to consist of thick accumulations of lava flows. The flow-like structure of the most recent lava deposits surrounding Sif Mons is especially bright in the radar illumination because of the roughness of the material. A fracture system, or rift, emanates from the southeastern flank of Gula Mons and extends several hundred kilometers beyond the edge of the frame. MAGELLAN PROJECT OFFICE P-38346BC 4/12/91 A shaded-relief perspective view of Venus prepared from Magellan data, that shows two large shield volcanoes, Sif (left) and Gula (right), located in the Eistla Region. The superimposed colors represent the radiothermal emissivity as given by the scale at right. Emissivity is a measure of the surface's ability to radiate energy, and depends primarily on the material's electrical properties. The 5-degree grid spacing is equivalent to 528 kilometers (328 miles). Both volcanoes are thought to consist of thick accumulations of lava flows. Note the relatively low values of emissivity associated with the summits, a property often found at higher elevations on Venus that is possibly the result of a change in the mineralogy as the ambient temperature and pressure drop. A fracture system, or rift, emanates from the southeastern flank of Gula Mons and extends several hundred kilometers beyond the edge of the frame. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-38346CC 4/12/91 A shaded-relief perspective view of a region surrounding the 10-km-high Maxwell Montes on Venus, prepared from Magellan data. The superimposed colors represent the radiothermal emissivity of the region as given in the scale at right. Emissivity is a measure of the surface's ability to radiate energy, and depends primarily on the material's electrical properties. The higher elevations of Maxwell display some of the lowest values of emissivity found on the planet; these low values probably result from changes in the surface mineralogy of volcanic flows when exposed for long periods of time to the lower ambient temperatures and pressures found at high altitudes. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-38359 MGN-50 5/21/91 This image compares Magellan data acquired in August 1990 during the initial test of the radar system (black and white insets), with data acquired by the spacecraft in April 1991 (color background). The area is in the southern hemisphere of Venus, and represents an area about 540 kilometers (335 miles) on a side, centered on latitude 35 degrees south and longitude 294 degrees east. The Magellan radar illuminates the surface from the left. The northern and eastern parts of the area consist of plains, which appear moderately-dark to dark on the radar image because they are relatively smooth at a scale comparable to the wavelength of the radar, 12.5 centimeters (about 5 inches). The bright terrain in the southwestern part of the image is about 500 to 700 meters (1640 to 2300 feet) higher than the plains; it is characterized by abundant faults and fractures, which appear as straight to gently curved bright lines. Many of these linear features are large enough to infer that they are graben, which are troughs bounded on both sides by faults. However, many of them are too narrow to determine if they are faults or simply fractures that have roughened the surface. This elevated faulted and fractured region is part of a large east-west elongated ridge mapped by the Pioneer Venus radar altimeter; the portion shown here is about midway between Themis Regio and Tefnut Mons. The plains are probably underlain by volcanic lavas. The various shades indicate that minor differences in surface roughness are present, and these may be used to map out the distribution of different lavas. The small, bright patches on the plains represent places where the lava surfaces are relatively rough. Just left of the center of the image is a sharply defined volcanic crater about 15 kilometers (9.3 miles) in diameter. Immediately north of this crater are numerous round spots about 2-4 kilometers (1-2 miles) across that are small volcanic domes. The low- resolution strip along the eastern edge of this image represents earth- based Arecibo data at a resolution about 20 times coarser than that of the Magellan data. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-38360 MGN-51 5/21/91 This false-color Magellan image shows the volcano Sapas Mons, located in the broad equatorial rise known as Atla Regio (8 degrees north latitude, 188 degrees east longitude). The area shown is approximately 650 kilometers (400 miles) on a side. The volcano itself is about 400 kilometers (250 miles) across and rises 1.5 kilometers (0.9 miles) above the local terrain. It is about 4.5 km above the mean planetary radius. The flanks of the volcano are composed of numerous overlapping lava flows. The dark flows on the lower right are thought to be smoother than the brighter flows near the central part of the volcano. Many of the flows appear to have erupted along the flanks of the volcano, rather than from the summit. This type of flank eruption is common on large volcanoes on the Earth, such as the Hawaiian volcanoes. The summit area consists of a pair of flat-topped mesas, whose smooth tops give a relatively dark appearance in the radar image. Also seen near the summit are groups of pits, some as large as 1 kilometer (0.6 miles) across. These are thought to have formed when underground chambers of magma were drained through other subsurface tubes, leading to a collapse at the surface. A 20- kilometer (12.5-mile) diameter impact crater northeast of the volcano is partially buried by the lava flows. Little was known about the Atla Regio rise prior to Magellan. The new data, taken in February 1991, show the region to be composed of at least five large volcanic edifices such as Sapas Mons, which are commonly linked by complex systems of fractures or rift zones. By analogy with similar features on the Earth, Atla Regio is thought to result from upwellings of large volumes of molten rock from the interior of Venus known as "hot spots." MAGELLAN PROJECT OFFICE P-38387 6/5/91 Many of the impact craters of Venus revealed by Magellan have characteristics unlike craters on any other planetary body. This 30- kilometer (18.6-mile) diameter crater, named Adivar crater for the Turkish educator and author Halide Adivar (1883-1964), is located just north of the western Aphrodite highland (9 degrees north latitude, 76 degrees east longitude). Surrounding the crater rim is ejected material which appears bright in the radar image due to the presence of rough fractured rock. A much broader area has also been affected by the impact, particularly to the west of the crater. Radar-bright materials, including a jet-like streak just west of the crater, extend for over 500 kilometers (310 miles) across the surrounding plains. A darker streak, in a horseshoe or paraboloidal shape, surrounds the bright area. Radar-dark (i.e., smooth) paraboloidal streaks were observed around craters in earlier Magellan images, but this is a rare bright crater streak. These unusual streaks, seen only on Venus, are believed to result from the interaction of crater materials (the meteoroid, ejecta, or both) and high-speed winds in the upper atmosphere. The precise mechanism that produces the streaks is poorly understood, but it is clear that the dense atmosphere of Venus plays an important role in the cratering process. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38388 6/5/91 This Magellan full resolution mosaic, centered at 12.3 north latitude, 8.3 east longitude, shows an area 160 kilometers (96 miles) by 250 kilometers (150 miles) in the Eistla region of Venus. The prominent circular features are volcanic domes, 65 kilometers (39 miles) in diameter with broad flat tops less than 1 kilometer (.6 mile) in height. Sometimes referred to as "pancake" domes, they represent a unique category of volcanic extrusions on Venus formed from viscous (sticky) lava. The cracks and pits commonly found in these features result from cooling and the withdrawal of lava. A less viscous flow was emitted from the northeastern dome toward the other large dome in the southwest corner of the image. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38434 6/14/91 This Magellan image shows a tectonically disrupted zone in the Thetis region of Venus. The image, centered on 15 degrees south latitude, 163 east longitude, is roughly 1,600 kilometers (992 miles) by 1,850 kilometers (1,147 miles). The bright arcuate features, which consist of numerous closely-spaced ridges and troughs, mark the locations of exceptionally deep chasmata (canyons). The chasmata commonly terminate at or wrap around circular corona structures, such as the 500 kilometers (310 miles) diameter feature in the lower right. The eastern portion of Dali Chasma extends from the left edge of the image and terminates at a corona-like feature near the center of the image. Dali Chasma is up to 4 kilometers (3 miles) deep in the area pictured. Diana Chasma, with comparable depths, extends from the lower left to the lower right of the image. These chasmata are part of the Aphrodite Terra equatorial highland, which is approximately 16,000 kilometers (9,920 miles) in length. The dramatic topography of the chasmata, and their association with the large Aphrodite structure, suggest that they may hold keys to understanding the global tectonic framework of Venus. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38449 6/14/91 This map shows the topography of a portion of the Thetis region of Venus, using data acquired by the Magellan altimetry instrument. Colors represent the planetary radius, measured in kilometers. The 10-degree grid spacing is equivalent to approximately 1050 kilometers (651 miles). The east-west trending troughs near the center of the map are Diana and Dali Chasmata. These valleys are up to 4 kilometers (3 miles) deep in places. Slopes as steep as 25 degrees, extending over several kilometers, are found at the edges of the valleys. The existence of such dramatic relief suggests that active tectonic forces may be dynamically supporting the topography. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38450 6/14/91 This Magellan image shows part of the highland Ovda Regio. The superimposed colors represent the planetary radius (topography), measured in kilometers. The 10-degree grid spacing is equivalent to approximately 1,050 kilometers (651 miles). A thick flow of possibly viscous lava extends about 160 kilometers (99 miles) in the east-west direction near the center of the image. The topography indicates that the central region of the flow now lies nearly 1 kilometer (0.62 mile) lower than the edges of the flow. This may be the result of subsidence of the central area following the emplacement of the lava flow. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38451 6/14/91 This image shows false-color representation of the surface relief of Venus between longitudes 100 degrees and 190 degrees east, as measured by the altimeter aboard the Magellan spacecraft. The distance from top to bottom (pole-to-pole) is 19,000 kilometers (11,780 miles). Colors represent variations in planetary radius, measured in kilometers. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38452 6/14/91 A perspective view of the topography Dali (to left) and Diana (to right) towards the southwest at 15 degrees south latitude, just to the east of Aphrodite Terra on Venus. Vertical exaggeration is about twenty-to-one. These valleys are 4 kilometers (3 miles) deep and about 65 kilometers (40 miles) wide, with walls sloping down at angles as steep as 25 degrees. The data were obtained by Magellan's altimetry. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38471 6/19/91 This large lava-flow field, which is about 140 kilometers (87 miles) wide and 300 kilometers (186 miles) long, was deposited on the rugged uplands of Ovda Regio. Subsequently, dark smooth appearing materials were deposited atop the southeastern margins of the lavas and the rugged uplands. Finger- like lobes of lavas extend from the margins of the field in all directions, but generally away from the center of the field and the now-hidden source of the lavas. Unlike most lava flows on Venus, which are thin, some lobes of these lavas are estimated to be near 200 meters (660 feet) thick. Lobate flows on Earth that are this thick are evolved, silica-rich lavas such as trachytes and rhyolites; basalt flows in Hawaii are much thinner than the Venusian lobes. Compression of the upper parts of the lavas during flow has produced concentric ridge and trough segments, also called pressure ridges, on the surface of the flow. The Magellan altimeter shows that the surface of the flow is spoon-shaped and lower near the west- central part (left) than elsewhere. The reason for this shape is unclear, but up-welling and subsidence of lava and faulting are possibilities. There is evidence that substances such as pyrite, magnetite, or other conductors are present at the surface of the flow. These substances suggest exciting possibilities for the composition of the lava flow field or some other processes unrelated to the flow. Magellan scientists are pursuing the geological implications of this flow field. Center of lava flow field is at 6.0 degrees south and 95.5 degrees east. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38515 7/1/91 This Magellan radar mosaic shows a portion of the Lada Terra highlands on Venus. The image, centered near 60 degrees south latitude and 15 degrees east longitude, covers an area about 1600 kilometers (970 miles) north- south by about 1840 kilometers (1100 miles) east-west. The large circular feature in the north-west of the image is the 500 kilometer (300 mile) diameter Eithinoha corona. Corona are thought to have formed as hot magma within the Venus crust migrates towards the surface, causing up-bowing of the crust and formation of a ridged boundary surrounding a central region of volcanism. Several lava flows and small shields can be seen in the center of this structure. The bright lines extending away from the corona are cracks and rifts that are probably a direct result of the crustal stresses associated with the formation of the corona. The arch in the lower left of the image is the boundary of another large corona. Extensive volcanism has also occurred in the plains and gives them a patchy or mottled appearance. This plains-forming volcanism has flooded some surrounding higher material, such as the bright patches of tessera east and southeast of Eithinoha corona. Tessera consists of multiple sets of complex intersecting ridges and troughs and often forms large (100's of kilometers wide) continuous patches of elevated terrain. In this case, however, the tessera has been flooded and degraded by volcanic activity, suggesting that the tessera is one of the older features in this region. The narrow channel that can just be seen in the lower central portion of the image was probably formed by the flow of lava from within the tessera out to the surrounding plains to the southwest; lobate lava deposits can be seen at the end of the channel. Two well-preserved, 30-40 kilometer (18-24 mile) diameter impact craters are found in the north central plains and two small circular features in the south central tessera may be degraded impact craters. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-38515 MGN-58 7/26/91 This Magellan radar mosaic shows a portion of the Lada Terra highlands on Venus. The image, centered near 60 degrees south latitude and 15 degrees east longitude, covers an area about 1600 kilometers (970 miles) north- south by about 1,840 kilometers (1,100 miles) east-west. The large circular feature in the north-west of the image is the 500 kilometer (300 mile) diameter Eithinoha corona. Coronae are thought to have formed as hot magma within the Venus crust migrates towards the surface, causing up- bowing of the crust and formation of a ridged boundary surrounding a central region of volcanism. Several lava flows and small shields can be seen in the center of this structure. The bright lines extending away from the corona are cracks and rifts that are probably a direct result of the crustal stresses associated with the formation of the corona. The arch in the lower left of the image is the boundary of another large corona. Extensive volcanism has also occurred in the plains and gives them a patchy or mottled appearance. This plains-forming volcanism has flooded some surrounding higher material, such as the bright patches of tessera east and southeast of Eithinoha corona. Tessera consists of multiple sets of complex intersecting ridges and troughs and often forms large (100's of kilometers wide) continuous patches of elevated terrain. In this case, however, the tessera has been flooded and degraded by volcanic activity, suggesting that the tessera is one of the older features in this region. The narrow channel that can just be seen in the lower central portion of the image was probably formed by the flow of lava from within the tessera out to the surrounding plains to the southwest; lobate lava deposits can be seen at the end of the channel. Two well-preserved, 30-40 kilometer (18-24 mile) diameter impact craters are found in the north central plains and two small circular features in the south central tessera may be degraded impact craters. MAGELLAN PROJECT OFFICE P-38547 4/12/91 Topographic relief of western Eistla Regio, showing the volcanic mountains, Sif (the red dot at left center) and Gula (the gray dot at right center). The superimposed colors represent the altitude of the surface features, measured from the center of the planet in kilometers (see scale at right). The 10-degree grid spacing is equivalent to 1,056 kilometers (656 miles). Both volcanoes are thought to consist of thick accumulations of lava flows. A fracture system, or rift, emanates from the southeastern flank of Gula Mons and extends several hundred kilometers nearly to the edge of the frame. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-38548 7/1/91 This is a Magellan radar mosaic of a region approximately 1300 kilometers (806 miles) across, centered at 21 degrees north latitude, 1 degree east longitude. Left of center is the radar-bright elongated summit of Gula Mons, a 1.8 kilometer (1.1 mile)-high volcano. Radiating outward in all directions from the summit is a system of lava flows, most of which are several hundred kilometers (up to about 600 miles) long. Though many of these flows appear bright in the radar image, dark flows are also present. This variability in radar brightness is largely due to differences in surface roughness from one flow to another. Dark flows are smoother than bright flows. The darker flows may be similar to terrestrial pahoehoe lava flows, whereas, the brighter flows are likely similar to terrestrial aa flows, which have a very rough, blocky surface texture. Trending southeastward from Gula Mons is a system of radar-bright irregular lineaments. This is the northwest end of Eistla Regio, a broad system of fractures and fault scarps that extends for approximately 6000 kilometers (3720 miles) eastward toward Aphrodite Terra. The individual scarps appear bright in the radar both because they are rough textured and because they face in the general direction of the incident radar beam (similar to a sun- facing slope appearing bright in visible light). Gula Mons is surrounded by plains that are likely volcanic flood plains. At least five impact craters are present in this scene. One of these, at right center, is associated with a roughly parabolic shaped dark region. The crater lies near the apex of the parabola which widens and fades to the west. Approximately 10 percent of the craters on Venus are associated with this parabolic feature which, in all cases, widens westward in the direction the wind blows in Venus' upper atmosphere. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38605 8/2/91 This full resolution mosaicked image covers an area of approximately 100 kilometers by 120 kilometers (62 by 74 miles) and is located in the Lakshmi region of Venus at 47 degrees north latitude and 334 east longitude. Due to the dense Venusian atmosphere, primary impact craters of less than a 3 kilometer (2 mile) diameter are nonexistent. The dark circular region and associated central bright feature in this image are thought to be the remnants of a meteoroid smaller than the size necessary to create an impact crater entering the atmosphere at a low velocity (approximately 350 meters/second.) The central bright feature appears to be a cluster of small secondary impacts, ejecta and debris from the original meteor that broke up in the atmosphere. Even though most of the meteorite did not hit the surface, the atmospheric shock wave could be great enough to modify the surrounding region. One explanation for this radar dark circular formation, called dark margins, could be that the shock wave was energetic enough to pulverize the surface (smooth surfaces generally appear radar dark.) Another explanation is that the surface could be blanketed by a fine material that was formed by the original meteor's breakup through the atmosphere. More than half of the impact craters on Venus have associated dark margins, and most of these are prominently located left of center of the crater. This is another effect which could be caused by the dense atmosphere of Venus. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38606 8/2/91 This Magellan mosaic covers an area of approximately 228 kilometers by 228 kilometers (141 by 141 miles). It is centered at 9.3 degrees north latitude, 357.8 degrees east longitude in the Navka region. The radar illumination is from the left. The image shows a cluster of impact craters whose ejecta is distributed in a butterfly pattern rather than radially out from the craters. The impacting object probably broke up during its passage through the atmosphere causing the multiple craters. The asymmetrical distribution of ejecta is indicative of an impact from an oblique angle. The cluster is located in a fractured plain with radar bright lineaments intersecting in several directions. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38607 8/2/91 This full resolution radar mosaic from Magellan centered at 15 degrees north latitude, 351 degrees east latitude, contains an impact crater approximately 25 kilometers (16 miles) in diameter. The crater Cunitz possesses a radar-bright ejecta blanket and non-radial flow-like ejecta indicative of flow of a low-viscosity material. On the periphery of the radar-bright ejecta blanket "dark margins" with low backscatter values are observed. The crater floor contains relatively smooth material with numerous linear fractures reminiscent of lunar mare wrinkle ridges. The impact crater occurs in an area of highly fractured plains and apparently postdates fracturing as evidenced by the manner in which the ejecta material is directed by the fractures. The principle fractures trend roughly east-west and intersect nearly orthogonal with shorter fractures creating a polygonal pattern. Fainter troughs trend nearly north-south and are probably the youngest fractures. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38608 8/2/91 A portion of Lavinia Planitia (30 degrees south latitude, 338 degrees east longitude) is displayed in this image of the surface of Venus. The image covers a region approximately 75 kilometers by 135 kilometers (47 by 84 miles). Three dome shaped features, 8 to 15 kilometers (5 to 9 miles) in diameter, are seen in the southern part of the region. Analogues to these dome shaped features can be found in a number of different environments on Earth, such as Long Valley, California, and Valles, New Mexico. Tens of kilometers north of these domes is a small conical volcano, 8 kilometers (5 miles) in diameter and several hundred meters high. The 3 kilometer (2 mile) summit pit of the volcano suggests explosive eruptions, tectonic activity, or collapse of the summit. The volcanoes are surrounded by an abundance of lineaments and fractures. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38609 8/2/91 Data for this image were recorded by Magellan during the first cycle of Venus orbits in September 1990 using Magellan's synthetic aperture radar (SAR). North is towards the top of the image, and radar illumination is from the left at an incidence angle of 38 degrees. The image is centered at 20.2 degrees south latitude and 338.7 degrees east longitude, west of Alpha Regio in the Navka region of Venus, and covers a section of the surface approximately 150 kilometers (93 miles) in width by 200 kilometers (124 miles) in length. Two circular areas with low radar backscatter cross-sections can be seen in the image, and are most likely due to meteoroid-atmosphere interaction. Large, radar-dark regions like the ones in the image, often called "dark margins," have been observed in association with about half of the impact craters on Venus, and it is speculated that such regions are the product of atmospheric shock waves from impactors. A second hypothesis attributes the dark regions to fine deposits of material created on impact or by ablation during atmospheric transit. The dark margin in the southern half of the image appears to surround a small, irregular impact crater or multiple crater, though the feature to the north does not. This suggests that the latter was due to a smaller meteoroid, one destroyed during transit, but large enough to create a shock or pressure wave able to deform the surface. Both radar-dark areas are about 50 km (31 miles) in diameter. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38610 8/2/91 This Magellan image, located in the Navka region of Venus, covers an area approximately 212 kilometers (131 miles) wide and 405 kilometers (251 miles) long. The large circular structure, approximately 50 kilometers (31 miles) across, centered at 16 degrees south latitude and 352 degrees east longitude (about 1500 kilometers [930 miles] northwest of Alpha Regio) probably resulted from an upwelling of magma. There is an abundance of lineaments associated with this structure arranged radially around the rim while, at greater distances, the fractures are generally north-south trending. These fractures are thought to be the surface expression of numerous shallowly placed dikes, the orientation of which is controlled near the structure by stress associated with the magma chamber. Further away from the structure, the fractures may be controlled by a larger regional stress field. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38611 7/16/91 These radar images show an identical area on Venus (centered at 110 degrees longitude and 64 degrees north latitude) as imaged by the U.S. Magellan spacecraft in 1991 (left) and the U.S.S.R. Venera 15/16 spacecraft in the early 1980's (right). Illumination is from the left (or west) in the Magellan image (left) and from the right (or east) in the Venera image (right). Differences in apparent shading in the images are due to differences in the two radar imaging systems. Prior to Magellan, the Venera 15/16 data was the best available for scientists studying Venus. Much greater detail is visible in the Magellan image owing to the greater resolution of the Magellan radar system. In the area seen here, approximately 200 small volcanoes, ranging in diameter from 2 to 12 kilometers (1.2 to 7.4 miles) can be identified. These volcanoes were first identified as small hills in Venera 15/16 images and were predicted to be shield-type volcanoes constructed mainly from eruptions of fluid lava flows similar to those that produce the Hawaiian Islands and sea floor volcanoes - a prediction that was confirmed by Magellan. These small shield-type volcanoes are the most abundant geologic feature on the surface of Venus, believed to number in the hundreds of thousands, perhaps millions, and are important evidence in understanding the geologic evolution of the planet. The only other planet in our Solar System with this large number of volcanoes is Earth. Clearly visible in the Magellan image are details of volcano morphology, such as variation in slope, the occurrence and size range of summit craters, and geologic age relationships between adjacent volcanoes, as well as additional volcanoes that were not identifiable in the Venera image. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38665 7/26/91 This mosaic is a composite of three pre-Magellan data sets: Arecibo radar images, Pioneer Venus radar images, and Pioneer Venus altimetry and shows the area imaged by Magellan during its first eight weeks of mapping. The curved dark lines represent gaps in the Magellan data that occurred due to Deep Space Network (DSN) outages and spacecraft pointing errors. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38690 8/2/91 This Magellan image centered near 9.6 degrees north latitude, 189.5 degrees east longitude of an area 140 kilometers (87 miles) by 110 kilometers (68 miles) covers part of the eastern flank of the volcano Sapas Mons on the western edge of Atla Regio. The bright lobate features along the southern and the western part of the image, oriented in northeast to southwest directions, are lava flows that are rough at the 12.6 centimeter wavelength of the radar. These flows range in width from 5 kilometers to 25 kilometers (3 to 16 miles) with lengths of 50 kilometers to 100 kilometers (31 to 62 miles), extending off the area shown here. Additional radar-dark (smooth) flows are also present. The radar-bright linear structures in the northwest part of the image are interpreted to be faults and fractures possibly associated with the emplacement of magma in the subsurface. Located near the center of the image is a 20 kilometer- (12 mile-) diameter impact crater. This crater is superimposed on a northeast/southwest trending fracture while the southern part of the crater's ejecta blanket is covered by a 6 kilometer- (4 mile-) wide radar-bright lava flow. These relations indicate that the crater post dates an episode of fracturing and is older than the lava flows covering its southern edge. This is one of only a few places on Venus in which an impact crater is seen to be covered by volcanic deposits. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38691 8/2/91 This Magellan image shows an impact crater in the central Eistla Region of the equatorial highlands of Venus. It is centered at 15 degrees north latitude and 5 degrees east longitude. The image is 76.8 kilometers (48 miles) wide. The crater is slightly irregular in planform and approximately 6 kilometers (4 miles) in diameter. The walls appear terraced. Five or six lobes of radar-bright ejecta radiate up to 13.2 kilometers (8 miles) from the crater rim. These lobes are up to 3.5 kilometers (2 miles) in width and form a "starfish" pattern against the underlying radar-dark plains. The asymmetric pattern of the ejecta suggests the angle of impact was oblique. The alignment of two of the ejecta lobes along fractures in the underlying plains is apparently coincidental. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38707 8/2/91 This Magellan image is centered about 3.2 degrees north latitude, 194.9 degrees longitude in the eastern Ovda region of Venus. The image, which is 90 km (56 miles) in width and 80 km (50 miles) in length, shows some small volcanic domes on the flank of the volcano Maat. The bright flows to the east are most likely rough lava flows while the darker flows to the west are probably smoother flows. The dark flows do show some roughness, however, as can be seen by the structure in the flows to the southwest. These dark flows also have some debris that has been deposited on top of the flows. The debris may be fine material from the surrounding plains on top of the flow by wind or it may be ash from the volcano. Small volcanic domes are very common features on the surface of Venus, indicating that there has been much volcanic activity on the surface. Assuming that the central volcanic cone is symmetrical in shape and knowing the length of the cone's side and the incidence angle, radar foreshortening yields a height and slope of 688 meters and 8.2 degrees, respectively for the cone. These values are similar to heights and slopes of some volcanic cones on the Earth. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-38720 MGN-76 October 29, 1991 A portion of Western Eistla Regio is displayed in this three-dimensional perspective view of the surface of Venus. The viewpoint is located 1,310 kilometers (812 miles) southwest of Gula Mons at an elevation of 0.78 kilometers (0.48 mile). The view is to the northeast with Gula Mons appearing on the horizon. Gula Mons, a 3 kilometer (1.86 mile) high volcano, is located at approximately 22 degrees north latitude, 359 degrees east longitude. The impact crater Cunitz, named for the astronomer and mathematician Maria Cunitz, is visible in the center of the image. The crater is 48.5 kilometers (30 miles) in diameter and is 215 kilometers (133 miles) from the viewer's position. Magellan synthetic aperture radar data is combined with radar altimetry to develop a three-dimensional map of the surface. Rays cast in a computer intersect the surface to create a three- dimensional perspective view. Simulated color and a digital elevation map developed by the U.S. Geological Survey, are used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced at the JPL Multimission Image Processing Laboratory and is a single frame from a video released at the March 5, 1991, JPL news conference. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-38721 MGN-77 October 29, 1991 Gula Mons is displayed in this computer-simulated view of the surface of Venus. The viewpoint is located 110 kilometers (68 miles) southwest of Gula Mons at the same elevation as the summit, 3 kilometers (1.9 miles) above Eistla Regio. Lava flows extend for hundreds of kilometers across the fractured plains. The view is to the northeast with Gula Mons appearing at the center of the image. Gula Mons, a 3 kilometer (1.9 mile) high volcano, is located at approximately 22 degrees north latitude, 359 degrees east longitude in western Eistla Regio. Magellan synthetic aperture radar data is combined with radar altimetry to produce a three- dimensional map of the surface. Rays cast in a computer intersect the surface to create a three-dimensional perspective view. Simulated color and a digital elevation map developed by the U.S. Geological Survey are used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the JPL Multimission Image Processing Laboratory and is a single frame from a video released at the March 5, 1991, JPL news conference. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-38722 MGN-74 October 21, 1991 Sif Mons is displayed in this computer-simulated view of the surface of Venus. The viewpoint is located 360 kilometers (223 miles) north of Sif Mons at a height of 7.5 kilometers (4.7 miles) above the lava flows. Lava flows extend for hundreds of kilometers across the fractured plains shown in the foreground to the base of Sif Mons. The view is to the south. Sif Mons, a volcano with a diameter of 300 kilometers (186 miles) and a height of 2 kilometers (1.2 miles), appears in the upper half of the image. Magellan synthetic aperture radar data is combined with radar altimetry to produce a three-dimensional map of the surface. Rays, cast in a computer, intersect the surface to create a three-dimensional perspective view. Simulated color and a digital elevation map developed by the U.S. Geological Survey are used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced at the JPL Multimission Image Processing Laboratory and is a single frame from a video released at the March 5, 1991, JPL news conference. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-38723 MGN-73 October 21, 1991 A corona is displayed in this computer-simulated view of the surface of Venus. The viewpoint is located 150 kilometers (93 miles) north of Gula Mons at a height of 1.6 kilometers (1 mile) above the corona. The corona has a diameter of 97 kilometers (60 miles). The proposed name for the corona is Idem-Kuva, a Finno-Ugraic harvest spirit. Lava Flows extend for hundreds of kilometers across the fractured plains shown in the background. The viewpoint is to the north with Gula Mons to the south. Magellan synthetic aperture radar data is combined with radar altimetry to produce a three-dimensional map of the surface. Rays, cast in a computer, intersect the surface to create a three-dimensional perspective view. Simulated color and a digital elevation map developed by the U.S. Geological Survey are used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced at the JPL Multimission Image Processing Laboratory and is a single frame from a video released at the March 5, 1991, JPL news conference. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-38724 MGN-72 September 27, 1991 A portion of Western Eistla Regio is displayed in this three-dimensional perspective view of the surface of Venus. The viewpoint is located 1,100 kilometers (682 miles) northeast of Gula Mons at an elevation of 7.5 kilometers (4.6 miles). Lava flows extend for hundreds of kilometers across the fractured plains shown in the foreground, to the base of Gula Mons. We are looking to the southwest with Gula Mons appearing at the left just below the horizon. Gula Mons, a 3 kilometer (1.86 mile) high volcano, is located at approximately 22 degrees north latitude, 359 degrees east longitude. Sif Mons, a volcano with a diameter of 300 kilometers (180 miles) and a height of 2 kilometers (1.2 miles), appears to the right of Gula Mons. The distance between Sif Mons and Gula Mons is approximately 730 kilometers (453 miles). Magellan synthetic aperture radar data is combined with radar altimetry to develop a three-dimensional map of the surface. Ray tracing - rays as if from a light source are cast in a computer to intersect the surface - simulate a perspective view. Simulated color and a digital elevation map developed by Randy Kirk of the U.S. Geological Survey, are used to enhance small scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced at the JPL Multimission Image Processing Laboratory by Eric De Jong, Jeff Hall, and Myche McAuley, and is a single frame a video released at a March 5, 1991, JPL news conference. MAGELLAN PROJECT OFFICE P-38741 8/12/91 This remarkable "half crater" is located in the rift between Rhea and Theia Montes in Beta Regio. Radar illumination is from the left. The as yet unnamed crater is 37 (23 miles) kilometers in diameter and is located at latitude 29.91 degrees north, longitude 282.9 degrees east. It has been cut by many fractures or faults since it was formed by the impact of a large asteroid. The eastern half of the crater has been completely destroyed during the formation of a fault-valley that is up to 20 kilometers (12 miles) wide and apparently quite deep. A north-south profile through the very center of this crater is visible as a result of the downdropping and removal of the eastern half of the crater. This "profile view" gives a third dimension to the crater. Thus it will be beneficial to "illuminate" this area from the opposite side (right-looking) with the Magellan SAR during a later mapping cycle, permitting an even more detailed view of the geologic structure of this feature. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38809 8/12/91 This full-resolution radar mosaic from Magellan centered at 13.5 degrees South latitude, 161 degrees longitude shows a 5.5 kilometer (3.3 mile) high scarp north of Dali Chasma, in the Thetis Region of Venus. The bright region in the bottom one-third of the mosaic, is elevated above the darker material to the north (and separated from it by the scarp). At least 3 landslides from the scarp can be identified in the mosaic, along with the head scarps from which they came. These are the hummocky surfaces at center, just left of center, and just above right center. These landslides range up to 30 kilometers (18 miles) from the base of the scarp. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-38810 8/12/91 The comet-like tail trending northeast from this volcanic edifice is a relatively radar-bright deposit. The volcano, whose basal diameter is 5 kilometers (about 3 miles), is a local topographic high that has slowed down northeast trending winds enough to cause deposition of this material. The streak is 35 kilometers (about 22 miles) long and 10 kilometers (about 6 miles) wide. The volcano is located at the western end of Parga Chasma at 9.4 degrees south latitude, 247.5 degrees east longitude. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38811 8/12/91 Two unusual volcanic domes are shown in this Magellan full-resolution mosaicked image. The image covers an area 180 by 240 kilometers (120 by 160 miles) centered at 18.1 degrees north latitude, 303.52 degrees east longitude, just east of Beta Regio. The dome in the south center of the image is about 45 kilometers (30 miles) across, with a 20 kilometer (13 mile) caldera, or volcanic collapse crater, in the center. The dome in the northwest corner of the image is about 30 kilometers (20 miles) across with a small (5 kilometer or 3 mile) summit crater; the very bright radar return from the western flank of this dome indicates that it has steep slopes. The flanks of these volcanoes display prominent gullies which may have been formed by slumping of surface material or thermal erosion by lava flows. Variation in the brightness within the surrounding plains show the extent of lava flows which originated at these volcanoes. Arcuate fractures surrounding the southern edifice indicate that there has been subsidence (down-warping) of the dome following eruptive activity. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38827 8/12/91 This full-resolution radar mosaic from Magellan at 52 degrees north latitude, 170 degrees east longitude, shows a 94 kilometer (56 mile) segment of the longest channel discovered on Venus to date. The channel is approximately 1.8 kilometers (1.1 miles) wide. At over 7000 kilometers (4200 miles) long, it is at least several hundred kilometers longer than the Nile River, Earth's longest river; thus, making it the longest known channel in the solar system. Both ends of the channel are obscured, however, so its original length is unknown. This channel was initially discovered by the Soviet Venera 15-16 orbiters, which, in spite of their 1 kilometer resolution, detected over 1000 kilometers of the channel. These channel-like features are common on the plains of Venus. In some places they appear to have been formed by lava which may have melted or eroded a path over the plains' surface. They resemble terrestrial meandering rivers superficially. Most are 1-3 kilometers (.6 to 2 miles) wide, though one degraded channel is 12 kilometers (7.4 miles) wide. They often exhibit meanders, cutoff oxbows, and abandoned channel segments, though they are not as tightly sinuous as terrestrial rivers. Most are partly buried by younger lava plains, making their sources difficult to identify. A few have terminal deposits, vast radar-dark plains units associated with them, suggesting large flow volumes. These channels appear to be older than other channel types, as they are crossed by fractures and wrinkle ridges, and are often buried by other volcanic materials. In addition, they appear to run both upslope and downslope, suggesting that the plains formed and were later warped by regional tectonism. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 9110 MAGELLAN PROJECT OFFICE P-38828 8/12/91 This full-resolution radar mosaic from Magellan at 51 degrees north latitude, 168 degrees east longitude, shows a 140 kilometer (84 mile) segment of the longest channel discovered on Venus to date. The channel is approximately 1.8 kilometers (1.1 miles) wide. At over 7000 kilometers (4200 miles) long, it is at least several hundred kilometers longer than the Nile River, Earth's longest river; thus, making it the longest known channel in the solar system. Both ends of the channel are obscured, however, so its original length is unknown. This channel was initially discovered by the Soviet Venera 15-16 orbiters, which, in spite of their 1 kilometer resolution, detected over 1000 kilometers of the channel. These channel-like features are common on the plains of Venus. In some places they appear to have been formed by lava which may have melted or eroded a path over the plains' surface. They resemble terrestrial meandering rivers superficially. Most are 1-3 kilometers (.6 to 2 miles) wide, though one degraded channel is 12 kilometers (7.4 miles) wide. They often exhibit meanders, cutoff oxbows, and abandoned channel segments, though they are not as tightly sinuous as terrestrial rivers. Most are partly buried by younger lava plains, making their sources difficult to identify. A few have terminal deposits, vast radar-dark plains units associated with them, suggesting large flow volumes. These channels appear to be older than other channel types, as they are crossed by fractures and wrinkle ridges, and are often buried by other volcanic materials. In addition, they appear to run both upslope and downslope, suggesting that the plains formed and were later warped by regional tectonism. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38850 9/13/91 This compressed resolution radar mosaic from Magellan at 49 degrees north latitude, 165 degrees east longitude, shows a 600 kilometer (360 mile) segment of the longest channel discovered on Venus to date. The channel is approximately 1.8 kilometers (1.1 miles) wide. At over 7,000 kilometers (4,340 miles) long, it is at least several hundred kilometers longer than the Nile River, Earth's longest river, thus making it the longest known channel in the solar system. Both ends of the channel are obscured, however, so its original length is unknown. This channel was initially discovered by the Soviet Venera 15-16 orbiters, which, in spite of their 1 kilometer resolution, detected over 1,000 kilometers of the channel. These channel-like features are common on the plains of Venus. In some places they appear to have been formed by lava which may have melted or eroded a path over the plains' surface. They resemble terrestrial meandering rivers superficially. Most are 1-3 kilometers (0.6 to 2 miles) wide, though one degraded channel is 12 kilometers (7.4 miles) wide. They often exhibit meanders, cutoff oxbows, and abandoned channel segments, though they are not as tightly sinuous as terrestrial rivers. Most are partly buried by younger lava plains, making their sources difficult to identify. A few have terminal deposits, vast radar-dark plains units associated with them, suggesting large flow volumes. These channels appear to be older than other channel types, as they are crossed by fractures and wrinkle ridges, and are often buried by other volcanic materials. In addition, they appear to run both upslope and downslope, suggesting that the plains formed and were later warped by regional tectonism. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-38851 MGN-65 August 30, 1991 This compressed resolution radar mosaic from Magellan at 49 degrees north latitude, 165 degrees east longitude with dimensions of 460 x 460 kilometers (285 x 285 miles), shows a 600 kilometer (360 mile) segment of the longest channel discovered on Venus to date. The channel is approximately 1.8 kilometers (1.1 miles) wide. At over 7000 kilometers (4200 miles) long, it is over several hundred kilometers longer than the Nile River, Earth's longest river; thus, making it the longest known channel in the solar system. Both ends of the channel are obscured, however, so its original length is unknown. This channel was initially discovered by the Soviet Venera 15/16 orbiters, which, in spite of their 1 kilometer resolution, detected over 1000 kilometers of the channel. Channel-like features are common on the plains of Venus. In some places they appear to have been formed by lava which may have melted or thermally eroded a path over the plains' surface. Most are 1-3 kilometers (.6 to 2 miles) wide, though one degraded channel is 12 kilometers (7.4 miles) wide. They resemble terrestrial meandering rivers in some aspects with meanders, cutoff oxbows, and abandoned channel segments. However, Venus channels are not as tightly sinuous as terrestrial rivers. Most are partly buried by younger lava plains, making their sources difficult to identify. A few have vast radar-dark plains units associated with them, suggesting large flow volumes. These channels with large deposits appear to be older than other channel types, as they are crossed by fractures and wrinkle ridges, and are often buried by other volcanic materials. In addition, they appear to run both upslope and downslope, suggesting that the plains were warped by regional tectonism after channel formation. Restoration of the Magellan data is about 120 meters (400 feet). MAGELLAN PROJECT OFFICE P-38852 8/30/91 This map shows the location on Venus of the long lava channel named Hildr. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38853 8/30/91 This map shows the location on Venus of the long lava channel named Hildr. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38856 8/21/91 This Magellan mosaic is centered about 27 degrees south latitude and 200 degrees east longitude in the northern Imdr Region of Venus. The image, which is 600 kilometers x 600 kilometers (372 miles x 372), shows numerous wind streaks. Wind streaks are produced downwind of a topographic obstacle where debris is either deposited or removed. In this image, the bright teardrop shape streaks located downwind of small volcanic cones most likely are regions of non-deposition or scouring. Hence, these streaks are bright because the area surrounding the streak has been filled in by debris that makes the terrain smoother and therefore darker in the radar image. Those streaks that are dark are probably regions where there has been deposition. The debris in this image most likely came from two large impact craters. The crater Isabella is a 165-kilometer (102 mile) diameter crater located 400 kilometers (248 miles) southeast of the image. Some of the ejecta from Isabella can be seen in the lower right of the image. The crater Stanton is a 108-kilometer (67 mile) diameter crater located 300 kilometers (186 miles) north of the image. If one were to follow the wind streaks from the bottom of the image to the top, the streaks at the lower left are bright fan streaks downwind of volcanic cones. These streaks indicate an eastward wind direction. To the northeast are bright and dark streaks indicating a northeast flow. Moving to the northwest are hundreds of very fine dark streaks indicating a northeast flow. Directly east of these streaks are about thirty spectacular teardrop-shape bright streaks associated with small volcanic domes. These streaks also indicate a northeast wind flow towards the equator. Finally, in the upper left and lower right of the image are small lava channels. These channels may have formed by drainage of lava or they may be the result of lava erosion. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-38857 8/21/91 This spectacular Magellan image is centered on 30 degrees south latitude, 135 degrees east longitude, spans 3500 kilometers (2170 miles) from east to west (left to right), and shows the near-circular trough of Artemis Chasma. Its circular shape and size (2100 km or 1302 miles in diameter) make Artemis the largest corona identified to date on the surface of Venus. Artemis could encompass most of the U.S. from the Front Range of the Rockies (near Denver) to the West Coast and is approximately twice the diameter of the next-smaller corona Heng-O. Coronae are characterized by a ring of concentric features surrounding an interior which typically contains fractures of varying orientations and volcanic features ranging from individual flows and small (<20 kilometer [12 mile]) volcanoes up to large (>100 kilometers [62 mile]) shield volcanoes. Artemis contains complex systems of fractures, numerous flows and small volcanoes, and at least two impact craters, the larger of which is located in the lower left (southwest) quadrant of the feature. The ring of fractures that defines Artemis forms a steep trough with raised rims approximately 120 kilometers (74 miles) wide and with as much as 2.5 kilometers (1.6 miles) of relief from the rim crest to the bottom of the trough. Most coronae are thought to be related to upwelling of hot material from the interior of Venus in the form of plumes or diapirs, and Artemis may be an extensional trough related to such an upwelling event. Raised-rim troughs are most commonly found to be extensional features (those formed by forces which tend to pull apart the crust and lithosphere of a planet) but the unusual size and circularity of Artemis have led to the alternate suggestion that it may be a zone of intense compression and underthrusting, similar to oceanic subduction zones on Earth. Magellan scientists are currently examining this feature in detail to determine which, if either, of these hypotheses is correct. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-38870 MGN-66 August 30, 1991 A portion of the eastern edge of Alpha Regio is displayed in this three- dimensional perspective view of the surface of Venus. The viewpoint is located at approximately 30 degrees south latitude, 11.8 degrees east longitude at an elevation of 2.4 kilometers (3.8 miles). The view is to the northeast at the center of an area containing seven circular dome-like hills. The average diameter of the hills is 25 kilometers (15 miles) with maximum heights of 750 meters (2,475 feet). Three of the hills are visible in the center of the image. Fractures on the surrounding plains are both older and younger than the domes. The surrounding plains are both older and younger than the domes. The hills may be the result of viscous or thick eruptions of lava coming from a vent on the relatively level ground, allowing the lava to flow in an even lateral pattern. The concentric and radial fracture patterns on their surfaces suggests that a chilled outer layer formed, then further intrusion in the interior stretched the surface. An alternative interpretation is that domes are the result of shallow intrusions of molten lava, causing the surface to rise. If they are intrusive, then magma withdrawal near the end of the eruptions produced the fractures. The bright margins possibly indicate the presence of rock debris or talus at the slopes of the domes. Resolution of the Magellan data is about 120 meters (400 feet). Magellan's synthetic aperture radar is combined with radar altimetry to develop a three-dimensional map of the surface. A perspective view is then generated from the map. Simulated color and a process called radar-clinometry are used to enhance small-scale structures. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the JPL Multimission Image Processing Laboratory by Eric De Jong, Jeff Hall, Myche McAuley, and Randy Kirk of the United States Geological Survey, and is a single frame from the movie released at the May 29, 1991 Magellan news conference. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-38889 MGN-68 August 30, 1991 These two radar images are full resolution mosaics, showing where Magellan began its mapping of Venus on September 15, 1990 and then completed its primary mission - one cycle covering all of Venus' 360 degrees of longitude. Completion was achieved on May 16, 1991 with 83.7% of the surface imaged by Magellan. The bottom image shows data from the start of mapping on the right mosaicked with data at the end of cycle 1 on the left. The left side of the top mosaic shows radar imagery from the Soviet Venera 15/16 spacecraft. Resolution of Venera data is 1 kilometer (.62 miles), while Magellan's average resolution is 120 meters (400 feet) or about 10 times better than that obtained by Venera. Centered at 59 degrees north latitude and 330 east longitude, the images cover an area 260 kilometers (161 miles) by 210 kilometers (130 miles) where a steep scarp called Vesta Rupes meets the dark smooth plains of Lakshmi Planum at the top of the images. Vesta Rupes consists of ridges which in this image trend primarily west-northwest. It descends 1.5 to 2 kilometers (.93 to 1.24 miles) from Lakshmi Planum in the north to the plains in the south, which themselves are inclined to the north. The ridges are crosscut by troughs, implying that formation of the troughs came after the deformation that caused the ridges to form. The troughs and abundant pits may have formed from collapse after the withdrawal of lava from subsurface lava tubes and chambers. The plains at the southern part of the image contain small ridges and are adjacent to a complexly deformed area in the southwest which is typical of terrain on Venus called tessera. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-38890 MGN-67 August 30, 1991 These two Magellan radar images are centered about 60.5 degrees south latitude and 348.8 degrees east longitude in the eastern Lavinia Region of Venus. The images, which are 110 kilometers (68 miles) in length and 130 kilometers (81 miles) in width, are full resolution mosaics of 14 orbits. The bottom image was made during cycle 2 of the Magellan mission when the radar was looking to the right of the spacecraft and at an angle of 25 degrees. The top image was made at the beginning of the mission when the radar was looking to the left and at an angle of 20 degrees. The mission data at the lower left of the top image represents the beginning of radar mapping during cycle 1. Both images show an area with interesting troughs, which are collapse features. In the bottom image, the north-south trending trough has a bright side on the left and a dark side on the right, while in the top image it is reversed. This is because the side of the trough sloping away from the radar appears dark while the side facing the radar appears bright. Since the radar was looking from the right in the bottom image and from the left in the top image, the bright and dark sides for the trough are reversed between the top and bottom images. It is very useful to obtain right-looking and left-looking images of the same area because features may not be visible from the opposite look direction. For instance, there are some fractures that can only be seen in one image. In addition, the different incidence angles obtained in cycle 2 of the mission, will allow scientists to better understand the nature of the Venus surface. Resolution of the Magellan data is about 100 meters (400 feet). JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-38975 MGN-69 August 30, 1991 Landslides on Venus! The image on the left was taken in late November of 1990 during Magellan's first trip around Venus. The image on the right was taken July 23, as the Magellan spacecraft passed over the region for the second time. Each image is 24 kilometers (14.4 miles) across and 38 kilometers (23 miles) long, and is centered at 2 degrees south latitude and 74 degrees east longitude. This pair of Magellan images shows a region in Aphrodite Terra, within a steeply sloping valley that is cut by many fractures. In the center of the image on the right, a bright, flow-like area can be seen extending to the west (left) of a bright fracture. The bright, rough area has appeared and the fracture has changed position in the 8 months since the first image was made. A "Venusquake" may have occurred, producing a new scarp and causing a landslide (the bright area) to form. This is the first evidence of active tectonics occurring on other planets in the solar system. Resolution of the Magellan data is 120 meters (400 feet). JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-39065 MGN-70 September 27, 1991 Southwest Lakshmi Planum (plains) is bounded on the south by the Danu Montes (mountains). Lakshmi Planum is an elevated plateau plain that is bounded on all sides by mountain chains. Here, the Danu mountains have an angular fractured appearance. Chasms slice diagonally across the mountains in the lower left (southwest) corner of the image. Because of the steep slopes and the local relief of the mountains of several kilometers (2-3 miles), these fault-bounded troughs appear to zig-zag through the mountains when, in fact, they are probably straight if viewed from above. The radar view provides a perspective that would place the viewer's eye to the right 27 degrees above the horizon. Thus, slopes facing to the right can be seen completely, though dark, and slopes facing away to the left appear shortened, often seen only as thin bright lines. In the center of the image is a low volcanic dome 20 kilometers (12 miles) in diameter. This type of volcanic feature frequently occurs on the low plains. This dome on the edge of Lakshmi is deformed and faulted where it has been affected by the forces that created the Danu mountains. The image is 75 kilometers (46 miles) on a side. The center is at 60 degrees north latitude, 324.5 degrees east longitude. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-39066 MGN-70 September 27, 1991 This Magellan full-resolution image shows the northern part of the Akna Montes (Mountains) of Venus. The Akna range is a north-south trending ridge belt that forms the western border of the elevated smooth plateau of Lakshmi Planum (plains). The Lakshmi plateau plains are formed by extensive volcanic eruptions and are bounded by mountain chains on all sides. The plains appear to be deformed near the mountains. This suggests that some of the mountain building activity occurred after the plains formed. An impact crater (Official International Astronomical Union name Wanda, mapped first by the Soviet Venera 15/16 mission in 1984 at low resolution) with a diameter of 22 kilometers (14 miles) has formed by the impact of an asteroid into the Akna mountains. The crater has a rugged central peak and a smooth radar-dark floor, probably volcanic material. The crater does not appear to be much deformed by later crustal movement that uplifted the mountains and crumpled the plains. Material from the adjacent mountain ridge to the west, however, appears to have collapsed into the crater. Small pits seen to the north of the crater may be volcanic collapse pits a few kilometers across (1-2 miles). The ridge of the Akna mountains immediately to the west of the crater is 8 kilometers wide (5 miles). The area in the image is approximately 200 kilometers long and 125 kilometers wide (130 by 80 miles). This area is centered at 71.5 degrees north latitude, 324 degrees east longitude. The resolution of the Magellan radar system is 120 meters (400 feet). At this latitude, the radar views the surface from an angle of 23 degrees off vertical, creating a perspective as though a viewer were looking at the scene from the right (east) at an angle of 23 degrees above the surface. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-39092 September 27, 1991 This image illustrates the technique used to create one frame of the computer-generated flyover movie of Venus showing the large volcanos Sif and Gula Mons. The radar image mosaic produced by the Magellan spacecraft is shown in its normal presentation, as though viewed from directly overhead. Magellan also measures the elevation (topography) of the surface, directly using its radar as an altimeter, and indirectly through a technique called radargrammetry, in which the variations in brightness of the radar image are interpreted as variations in the slope of the surface. The red box represents the area of the mosaic used to create one movie frame. The cross at the corner of the red box marks the location of the "camera" above the surface. The blue line leads to a second cross at the center of the scene, while the two green lines mark the edges of the scene. The viewing location of the "camera" is also controlled in its height above the surface. Each movie frame is generated by calculating what the scene would look like from the "camera" position, looking in the chosen direction. The flat radar image is registered onto the elevation model, as though it were draped over the rises and falls of the terrain. The computer determines which part of the radar mosaic would be seen in each picture element (pixel) making up the scene. In order to create the movie, many frames are assembled in sequence, with the "camera" location and viewing direction moving smoothly along the desired flight path. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-39093 September 27, 1991 This image illustrates the flight path used to create the computer- generated flyover movie of Venus showing the large volcanos Sif and Gula Mons. The radar image mosaic produced by the Magellan spacecraft is shown in its normal presentation, as though viewed from directly overhead. Magellan also measures the elevation (topography) of the surface, directly using its radar as an altimeter, and indirectly through a technique called radargrammetry, in which the variations in brightness of the radar image are interpreted as variations in the slope of the surface. The red line represents the flight path of the computer's "camera". The camera starts at the upper left, loops around the summit of Sif, moves south and then east across a smooth plain, crossing two craters on the way. It then flies north up a bright chasm, directly over the summit of Gula. It moves back to the west and then east over the dark fallout streak from an impact crater. Finally it flies away to the northeast looking back toward the area it has covered. Each movie frame is generated by calculating what the scene would look like from the "camera" position, looking in the chosen direction. The flat radar image is registered onto the elevation model, as though it were draped over the rises and falls of the terrain. The computer determines which part of the radar mosaic would be seen in each picture element (pixel) making up the scene. In order to create the movie, many frames are assembled in sequence, with the "camera" location and viewing direction moving smoothly along the desired flight path. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-39144 10/21/91 This full-resolution mosaic centered at 9.4 degrees south latitude, 74 degrees east longitude in the Ovda Region of the Aphrodite Highlands on Venus is an anaglyph or combined image consisting of two data sets slightly displaced from each other and projected in red and blue. This produces a 3-dimensional or stereo effect when viewed through red and blue tinted glasses. Magellan "looked" at the surface from different incidence angles (44 and 24 degrees, from a line normal to the surface) as it passed over the same part of the surface in the first and second mapping cycle (November 1990 and July 1991, respectively). The ability to see both the radar image and differences in elevation together is valuable for geologic interpretation. The image, which is approximately 80 kilometers (49.6 miles) on a side, shows a smooth depression in the upper left of the frame. Surrounding this depression is a complex ridge-and-valley terrain that sits at a higher elevation. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-39145 10/21/91 This full-resolution mosaic centered at 2 degrees south latitude, 74 degrees east longitude is an anaglyph or combined image consisting of two data sets slightly displaced from each other and projected in red and blue. This produces a 3-dimensional or stereo effect when viewed through red and blue tinted glasses. Magellan "looked" at the surface from different incidence angles (44 and 24 degrees, from a line normal to the surface) as it passed over the same part of the surface in the first and second mapping cycle (November 1990 and July 1991, respectively). The brain perceives it as if there were two large eyes, one at each Magellan position, viewing the surface while discerning relief. The ability to see both the radar image and differences in elevation together is valuable for geologic interpretation. The image which is approximately 95 kilometers (58.9 miles) on a side shows scarps and troughs concentric to and radiating from a 75 kilometer (46.5 mile) depression. Surrounding the depression is fine scale complex ridge terrain which may have formed from several events of compression and extension in different directions. The fact that the depression appears dark and lacks most of these ridges may be attributed to flooding by smooth lava after some of the deformational events. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-39146 MGN-78 October 29, 1991 Three impact craters are displayed in this three-dimensional perspective view of the surface of Venus. The center of the image is located at approximately 27 degrees south latitude, 339 degrees east longitude in the northwestern portion of Lavinia Planitia. The viewpoint is located southwest of Howe Crater, which appears centered in the lower portion of the image. Howe is a crater with a diameter of 37.3 kilometers (23.1 miles) located at 28.6 degrees south latitude, 337.1 degrees east longitude. Danilova, a crater with a diameter of 47.6 kilometers (29.5 miles), located at 26.35 degrees south latitude, 337.25 degrees east longitude, appears above and to the left of Howe in the image. Aglaonice, a crater with a diameter of 62.7 kilometers (38.9 miles), located at 26.5 degrees south latitude, 340 degrees east longitude, is shown to the right of Danilova. Magellan synthetic aperture radar data is combined with radar altimetry to develop a three-dimensional map of the surface. Rays cast in a computer intersect the surface to create a three-dimensional perspective view. Simulated color and a digital elevation map developed by the U.S. Geological Survey are used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced at the JPL Multimission Image Processing Laboratory and is a single frame from a video released at the May 29, 1991, JPL news conference. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-39147 MGN-79 October 29, 1991 This Magellan image depicts a stereoscopic pair of an area on Venus with small volcanic domes. Stereoscopic images of Venus offer exciting new possibilities for scientific analysis of Venusian landforms, such as the domes shown here, impact craters, graben - long rifts bounded by faults - and other geologic features. Stereopsis, or a three-dimensional view of this scene, may be obtained by viewing with a stereoscope. One may also cut this photograph into two parts and look at the left image with the left eye and the right image with the right eye; conjugate images (the same features) should be about 5 centimeters (2 inches) apart when viewing. This area is located at 38.4 degrees south latitude and 78.3 degrees east longitude. The incidence, or look, angle of the left image is 28.5 degrees and that of the right image is 15.6 degrees. Radar illumination for both images comes from the left. A small dome at left center is about 140 meters (462 feet) high and 6 kilometers (3.7 miles) wide. Other domes with smaller relief can be perceived in three dimensions. At the smaller incidence angle used to acquire the image on the right, radar brightness is more sensitive to small changes in topography. This enhances the visibility of many of the domes in this scene. MAGELLAN PROJECT OFFICE P-39163 1/17/92 A portion of Western Eistla Regio is displayed in this three-dimensional perspective view of the surface of Venus. The viewpoint is located 725 kilometers (450 miles) southeast of Gula Mons, at an elevation of 1.2 kilometers (0.74 miles). A rift valley, shown in the foreground, extends to the base of Gula Mons, a 3 kilometer (1.86 miles) high volcano. We are looking to the northwest with Gula Mons appearing at the right on the horizon. Gula Mons is located at approximately 22 degrees north 359 degrees east. Sif Mons, a volcano with a diameter of 300 kilometers (180 miles) and a height of 2 kilometers (1.2 miles), appears to the left of Gula Mons in the background. Magellan synthetic aperture radar data is combined with radar altimetry to develop a three-dimensional map of the surface. Ray tracing is used to generate a perspective view from this map. The vertical scale is exaggerated approximately 23 times. Simulated color and a digital elevation map developed by the U. S. Geological Survey are used to enhance small scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced at the JPL Multimission Image Processing Laboratory by Eric De Jong, Jeff Hall, and Myche McAuley, and is a single frame from the movie released at the March 5, 1991, press conference. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109. Telephone (818) 354-5011 JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-39164 November 7, 1991 Stuart crater is displayed in this image of the surface of Venus, which was created in a computer using Magellan radar data. The viewpoint is located east of Stuart crater at an elevation above the surface of 1.6 kilometers (1 mile). Stuart crater, named for Mary Stuart, Queen of Scots, is located at approximately 30.75 degrees south latitude, 20.20 degrees east longitude, and has a diameter of 67 kilometers (41.5 miles). The image is made by combining in a computer Magellan synthetic aperture radar data with radar altimetry. The computer processing produces a three-dimensional perspective of the surface. The vertical scale in this perspective has been exaggerated 22.5 times. Simulated color and a digital elevation map developed by the U.S. Geological Survey are used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory, and is a single frame from a video released at the May 29, 1991, JPL news conference. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-39165 November 7, 1991 A volcano with a fluted rim is displayed in this image of the surface of Venus which was created in a computer from Magellan radar data. The viewpoint is located 50 kilometers (31 miles) northwest of the volcano, at a height of 0.6 kilometers (0.47 miles) above the volcano. The image is centered at 5.5 degrees east longitude, 18 degrees south latitude, 25 kilometers (16 miles) north of the complex-ridged terrain of Alpha Regio. The volcano is approximately 66 kilometers (41 miles) across at the base, with a concave summit 35 kilometers (22 miles) in diameter. Dark lava flows emanate from a shallow summit pit. The sides of the volcanic edifice are characterized by radiating ridges and valleys that impart a fluted appearance. The image is made by combining in a computer Magellan synthetic aperture radar data with radar altimetry. The computer processing produces a three-dimensional perspective of the surface. Simulated color and a digital elevation map developed by the U.S. Geological Survey, are used to enhance small scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced at the JPL Multimission Image Processing Laboratory, and is a single frame from a video released at the May 29, 1991, JPL news conference. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-39166 November 7, 1991 Gula Mons and Cunitz crater are displayed in this image of the surface of Venus which was created in a computer using Magellan radar data. The viewpoint is located 1,310 kilometers (812.2 miles) west of Gula Mons and is 1.6 kilometers (1 mile) above the surface at Eistla Regio. The view is to the east with Gula Mons appearing on the horizon. Gula Mons, a 3- kilometer (1.9-mile) high volcano, is located at approximately 22 degrees north latitude, 359 degrees east longitude in western Eistla Regio. The impact crater displayed in the center of the image is named after the astronomer and mathematician, Maria Cunitz. Cunitz crater is 48.5 kilometers (30 miles) in diameter and is located at approximately 14.5 degrees north latitude, 350 degrees east longitude. The image is made by combining Magellan synthetic aperture radar data with radar altimetry. The computer processing produces a three-dimensional perspective of the surface. The vertical scale in this perspective has been exaggerated 22.5 times. Simulated color and a digital elevation map developed by the U.S. Geological Survey are used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory, and is a single frame from a video released at the March 5, 1991, JPL news conference. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-39167 1/17/92 A caldera on Gula Mons is displayed in this computer-simulated view of the surface of Venus. The viewpoint is located at a height of 1.6 kilometers (1 mile) above the caldera. The caldera has a diameter of approximately 25 kilometers (15.5 miles). Lava flows extend for hundreds of kilometers across the fractured plains shown in the background. The view is to the north. Magellan synthetic aperture radar data is combined with radar altimetry to produce a three-dimensional map of the surface. Rays cast in a computer intersect the surface to create a three-dimensional perspective view. The vertical scale is exaggerated approximately 23 times. Simulated color and a digital elevation map developed by the U. S. Geological Survey are used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory, and is a single frame from a video released at a March 5, 1991, JPL news conference. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109. Telephone (818) 354-5011 MAGELLAN PROJECT OFFICE P-39168 1/17/92 A portion of Alpha Regio is displayed in this three-dimensional perspective view of the surface of Venus.Alpha Regio, a topographic upland approximately 1300 kilometers across, is centered on 25 degrees south latitude, 4 degrees east longitude. In 1963, Alpha Regio was the first feature on Venus to be identified from earth-based radar. The radar-bright area of Alpha Regio is characterized by multiple sets of intersecting trends of structural features such as ridges, troughs, and flat-floored fault valleys that, together, form a polygonal outline. Directly south of the complex ridged terrain is a large ovoid-shaped feature named Eve. The radar-bright spot located centrally within Eve marks the location of the prime meridian of Venus. Magellan synthetic aperture radar data is combined with radar altimetry to develop a three-dimensional map of the surface. Ray tracing is used to generate a perspective view from this map. The vertical scale is exaggerated approximately 23 times. Simulated color and a digital elevation map developed by the U. S. Geological Survey are used to enhance small scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced at the JPL Multimission Image Processing Laboratory by Eric De Jong, Jeff Hall, and Myche McAuley, and is a single frame from the movie released at the March 5, 1991, press conference. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109. Telephone (818) 354-5011 MAGELLAN PROJECT OFFICE P-39175 10/21/91 This Magellan image is centered at 4 degrees south latitude and 157 degrees east longitude in the Thetis Region of Venus. The image is approximately 525 kilometers (326 miles) wide at the base and shows Franklin, an impact crater 72 kilometers (45 miles) in diameter. The crater is complex, characterized by a partial central ring and a floor flooded by radar-dark materials. Hummocky, rough-textured ejecta extend up to 60 kilometers (37 miles) from the crater rim. The crater is most remarkable for the extensive flows that appear to have travelled over 300 kilometers (186 miles) from the crater walls. These flows are striking against the darker underlying plains and may represent large volumes of impact melt. Alternatively, they may be the result of volcanic material released from the subsurface during the cratering event. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-39191 MGN-75 October 21, 1991 This Magellan mosaic is of an area centered about 67 degrees north latitude and 90 degrees east longitude in the Tellus Region of Venus. The area imaged is 340 kilometers (211 miles) in length and 190 kilometers (118 miles) in width and shows a possible dune field on Venus. The dune field is located in a valley between Ishtar Terra and Meshkenet Tessera. It covers about 17,120 square kilometers (6,506 square miles) and has about 40 radar-bright linear wind streaks. The dunes range from 0.5 to 10 kilometers (0.3 to 6.2 miles) in length, and are about 0.2 kilometers (0.1 miles) wide and have an average spacing of 0.5 kilometers (0.3 miles). The orientation of the dunes and the wind streaks in the southern part of the field indicates a southeast to northeast wind flow that shifts to a westward flow in the northern part of the field. Two bright streaks near a 12-kilometer (7.4 mile) diameter crater north of the dune field also suggest westward wind flow. The streaks indicate that the dunes are oriented perpendicular to the prevailing winds. On Earth, windblown sand accumulates in dunes usually at angles no greater than 33 degrees. With radar, the faces of dunes normally can only be seen with look-angles of less than 33 degrees aimed directly into the faces of the dunes. It is assumed that windblown dunes would form the same way on Venus. These dunes, however, were viewed at an angle of 22 degrees and most of them are parallel to the radar angle rather than perpendicular to it. They may be visible to the radar because of the change in roughness across the dunes. Rough surfaces show up brightly in radar illumination. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-39194 October 29, 1991 This full-resolution mosaic centered at 1.3 degrees north latitude, 73.8 degrees east longitude in the Ovda Region of the Aphrodite Highlands on Venus is an anaglyph or combined image consisting of two data sets slightly displaced from each other and projected in red and blue. This produces a 3-dimensional or stereo effect when viewed through red and blue tinted glasses. Magellan "looked" at the surface from different incidence angles (44 and 24 degrees, from a line perpendicular to the surface) as it passed over the same part of the surface in the first and second mapping cycle (November 1990 and July 1991, respectively). The ability to see both the radar image and differences in elevation together is valuable for geologic interpretation. The image, which is of an area approximately 100 kilometers (62 miles) on a side, shows a complex pattern of troughs, ridges, and depressions. A steep ridge running approximately northeast- southwest marks the boundary between a zone of fractured plains to the northwest and a deep quasi-circular depression to the southeast. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-39195 October 29, 1991 This full-resolution mosaic centered at 59.1 degrees south latitude, 86.5 degrees east longitude in the Lada Terra Region on Venus is an anaglyph, or combined image, consisting of two data sets slightly displaced from each other and projected in red and blue. This produces a 3-dimensional or stereo effect when viewed through red and blue tinted glasses. Magellan "looked" at the surface from different incidence angles (20 and 14 degrees from a line perpendicular to the surface) as it passed over the same part of the surface in the first and second mapping cycles (November 1990 and July 1991, respectively). The ability to see both the radar image and differences in elevation together is valuable for geologic interpretation. The image is of an area approximately 100 kilometers (62 miles) on a side and shows a deep trough approximately 110 kilometers (68 miles) long, and 8 to 12 kilometers (5 to 7 miles) wide. Analysis of geometric distortions in the two images shows the trough to be about 800 meters (0.5 mile) deep. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-39196 October 29, 1991 This full-resolution mosaic centered at 1.9 degrees south latitude, 73.8 degrees east longitude in the Ovda Region of the Aphrodite Highlands on Venus is an anaglyph or combined image consisting of two data sets slightly displaced from each other and projected in red and blue. This produces a 3-dimensional or stereo effect when viewed through red and blue tinted glasses. Magellan "looked" at the surface from different incidence angles (44 and 24 degrees, from a line perpendicular to the surface) as it passed over the same part of the surface in the first and second mapping cycles (November 1990 and July 1991, respectively). The ability to see both the radar image and differences in elevation together is valuable for geologic interpretation. The image, which is of an area approximately 200 kilometers (124 miles) on a side, shows an extremely complex, tectonically disrupted terrain which displays dramatic topography. The dark circular region near the center of the image sits as much as 3 kilometers (2 miles) lower than the ridges to the west. The complex pattern of ridges and troughs indicates the region has experienced a series of tectonic events, including faulting, uplift, and collapse. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-39224 MGN 80 October 29, 1991 The northern hemisphere is displayed in this global view of the surface of Venus. The north pole is at the center of the image, with 0 degrees, 90 degrees, 180 degrees, 270 degrees east longitudes at the 6, 3, 12, and 9 o'clock positions, respectively, of an imaginary clock face. Magellan synthetic aperture radar mosaics from the first cycle of Magellan mapping are mapped onto a computer-simulated globe to create this image. Data gaps are filled with Pioneer-Venus Orbiter data, or a constant mid-range value. Simulated color is used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory, and is a single frame from a video released at the October 29, 1991, JPL news conference. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-39225 MGN 81 October 29, 1991 This global view of the surface of Venus is centered at 180 degrees east longitude. Magellan synthetic aperture radar mosaics from the first cycle of Magellan mapping are mapped onto a computer-simulated globe to create this image. Data gaps are filled with Pioneer-Venus Orbiter data, or a constant mid-range value. Simulated color is used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory, and is a single frame from a video released at the October 29, 1991, JPL news conference. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-39226 MGN-82 October 29, 1991 This full resolution radar mosaic from Magellan at 49 degrees south latitude, 273 degrees east longitude of an area with dimensions of 130 by 190 kilometers (81 by 118 miles), shows a 200 kilometer (124 mile) segment of a sinuous channel on Venus. The channel is approximately 2 kilometers (1.2 miles) wide. These channel-like features are common on the plains of Venus. In some places they appear to have been formed by lava which may have melted or thermally eroded a path over the plains' surface. Most are 1 to 3 kilometers (0.6 to 2 miles) wide. They resemble terrestrial rivers in some respects, with meanders, cutoff oxbows, and abandoned channel segments. However, Venus channels are not as tightly sinuous as terrestrial rivers. Most are partly buried by younger lava plains, making their sources difficult to identify. A few have vast radar-dark plains units associated with them, suggesting large flow volumes. These channels appear to be older than other channel types on Venus, as they are crossed by fractures and wrinkle ridges, and are often buried by other volcanic materials. In addition, they appear to run both upslope and downslope, suggesting that the plains were warped by regional tectonism after channel formation. Resolution of the Magellan data is about 120 meters (400 feet). MAGELLAN PROJECT OFFICE P-39230 10/29/91 This full resolution radar mosaic from Magellan at 50 degrees south latitude, 273 degrees east longitude with dimensions of 80 by 60 kilometers (50 by 37 miles), shows a 90 kilometer (56 mile) segment of a sinuous channel on Venus. The channel is approximately 2 kilometers (1.2 miles) wide. These channel-like features are common on the plains of Venus. In some places they appear to have been formed by lava which may have melted or thermally eroded a path over the plains' surface. Most are 1 to 3 kilometers (0.6 to 2 miles) wide. They resemble terrestrial rivers in some respects, with meanders, cutoff oxbows, and abandoned channel segments. However, Venus channels are not as tightly sinuous as terrestrial rivers. Most are partly buried by younger lava plains, making their sources difficult to identify. A few have vast radar-dark plains units associated with them, suggesting large flow volumes. These channels appear to be older than other channel types on Venus, as they are crossed by fractures and wrinkle ridges, and are often buried by other volcanic materials. In addition, they appear to run both upslope and downslope, suggesting that the plains were warped by regional tectonism after channel formation. Resolution of the Magellan data is about 120 meters (400 feet). Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-39326 MGN-83 October 29, 1991 Maat Mons is displayed in this three-dimensional perspective view of the surface of Venus. The viewpoint is located 560 kilometers (347 miles) north of Maat Mons at an elevation of 1.7 kilometers (1 mile) above the terrain. Lava flows extend for hundreds of kilometers across the fractured plains shown in the foreground, to the base of Maat Mons. The view is to the south with Maat Mons appearing at the center of the image on the horizon. Maat Mons, an 8 kilometer (5 mile) high volcano, is located at approximately 0.9 degrees north latitude, 194.5 degrees east longitude. Magellan synthetic aperture radar data is combined with radar altimetry to develop a three-dimensional map of the surface. Rays cast in a computer intersect the surface to create a three-dimensional perspective view. Simulated color and a digital elevation map developed by the U. S. Geological Survey, are used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced at the JPL Multimission Image Processing Laboratory. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-39342 November 25, 1991 Every 243 days (one Venus "day"), the Magellan spacecraft returns to the same position over the surface of the planet. This provides the opportunity to view the same terrain with a different set of radar instrument parameters. This image pair shows two views of an area in the Ovda Region of the Aphrodite highlands (center latitude 8 degrees south, longitude 74 degrees east). The area shown is approximately 80 kilometers (49.6 miles) across and 220 kilometers (136.4 miles) top-to-bottom. The left image was acquired in November 1990 during the first mapping cycle; the right image was acquired in July 1991 during the second mapping cycle. The images were acquired at different view angles (43 degrees from vertical in cycle 1, 23 degrees from vertical in cycle 2). This difference creates slightly different distortions related to topographic variations. By viewing the images one to each eye (left image to left eye, right image to right eye), a three dimensional "stereo" effect is created. A total of about 2.6 kilometers (1.6 miles) of elevation difference are present in this scene. Fine details of topography are revealed by this technique, which greatly aid in the geological interpretation of the image data. The smooth radar-dark area in the lower part of the frame is seen to be a depression, which is surrounded by complex ridge-and-valley terrain that sits at a higher elevation. Mission planners anticipate that Magellan will operate in "stereo" mode, with incidence angles complementary to cycle one, during most of cycle three in 1992. MAGELLAN PROJECT OFFICE P-39374 11/4/91 This image shows color-coded elevation overlaid on a shaded relief perspective view of Alpha Regio, based on Magellan altimetry. This area, about 750 miles across, is one of the most topographically complex to be found on Venus, and shows surface roughness at virtually all scale sizes from a few inches up to a hundred miles. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-39375 11/4/91 This image shows Mercator (above) and polar stereographic (below) color- coded maps of elevations on Venus, as derived from the first eight months of Magellan altimetric observations. A small amount of shading has been added to emphasize steep slopes. The large highland area in the north is Ishtar Terra, containing the highest mountains (called Maxwell) on the planet. Aphrodite Terra, another important highland, is draped along the equator to the right. Regions shown in gray have not yet been observed by Magellan, but show the coarser results of the 1978 Pioneer Venus mission. Over 90% of the planet has been mapped in this image. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-39380 MGN-84 November 7, 1991 The western half of Venus is displayed in this simple cylindrical map of the planet's surface. The left edge of the image is at 240 degrees east longitude, the right edge at 67.5 degrees east longitude. The top and bottom of the image are at 90 degrees north latitude and 90 degrees south latitude, respectively. Magellan synthetic aperture radar mosaics from the first cycle of Magellan mapping are mapped onto a rectangular latitude- longitude grid to create this image. Data gaps are filled with Pioneer- Venus Orbiter altimetric data, or a constant mid-range value. Simulated color is used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-39381 MGN-85 November 7, 1991 The eastern half of the planet is displayed in this simple cylindrical map of the surface of Venus. The left edge of the image is at 52.5 degrees east longitude, the right edge of 240 degrees east longitude. The top and bottom of the image are at 90 degrees north latitude and 90 degrees south latitude, respectively. Magellan synthetic aperture radar mosaics from the first cycle of the Magellan mapping are mapped onto a rectangular latitude- longitude grid to create this image. Data gaps are filled with Pioneer- Venus Orbiter altimetric data, or a constant mid-range value. Simulated color is used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory. MAGELLAN PROJECT OFFICE P-39570 1/17/92 This global view of the surface of Venus is centered at 0 degrees east longitude. Magellan synthetic aperture radar mosaics from the first cycle of Magellan mapping are mapped onto a computer-simulated globe to create this image. Data gaps are filled with Pioneer-Venus Orbiter data, or a constant mid-range value. Simulated color is used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory, and is a single frame from a video released at the October 29, 1991, JPL news conference. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109. Telephone (818) 354-5011 MAGELLAN PROJECT OFFICE P-39571 1/17/92 This global view of the surface of Venus is centered at 90 degrees east longitude. Magellan synthetic aperture radar mosaics from the first cycle of Magellan mapping are mapped onto a computer-simulated globe to create this image. Data gaps are filled with Pioneer-Venus Orbiter data, or a constant mid-range value. Simulated color is used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory, and is a single frame from a video released at the October 29, 1991, JPL news conference. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109. Telephone (818) 354-5011 MAGELLAN PROJECT OFFICE P-39572 1/17/92 This global view of the surface of Venus is centered at 270 degrees east longitude. Magellan synthetic aperture radar mosaics from the first cycle of Magellan mapping are mapped onto a computer-simulated globe to create this image. Data gaps are filled with Pioneer-Venus Orbiter data, or a constant mid-range value. Simulated color is used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory, and is a single frame from a video released at the October 29, 1991, JPL news conference. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109. Telephone (818) 354-5011 MAGELLAN PROJECT OFFICE P-39573 1/17/92 The southern hemisphere is displayed in this global view of the surface of Venus. The south pole is at the center of the image, with 0 degrees, 90 degrees, 180 degrees, 270 degrees east longitudes at the 12, 3, 6, and 9 o'clock positions, respectively, of an imaginary clock face. Magellan synthetic aperture radar mosaics from the first cycle of Magellan mapping are mapped onto a computer-simulated globe to create this image. Data gaps are filled with Pioneer-Venus Orbiter data, or a constant mid-range value. Simulated color is used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109. Telephone (818) 354-5011 MAGELLAN PROJECT OFFICE P-39631 2/5/92 The northern hemisphere is displayed in this global view of the surface of Venus. The north pole is at the center of the image, with 0 degrees, 90 degrees, 180 degrees, 270 degrees east longitudes at the 6, 3, 12, and 9 o'clock positions, respectively, of an imaginary clock face. Magellan synthetic aperture radar mosaics from the first cycle of Magellan mapping, and a 5 degree latitude-longitude grid, are mapped onto a computer- simulated globe to create this image. Data gaps are filled with Pioneer- Venus Orbiter data, or a constant mid-range value. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-39632 2/5/92 The southern hemisphere is displayed in this global view of the surface of Venus. The south pole is at the center of the image, with 0 degrees, 90 degrees, 180 degrees, 270 degrees east longitudes at the 12, 3, 6, and 9 o'clock positions, respectively, of an imaginary clock face. Magellan synthetic aperture radar mosaics from the first cycle of Magellan mapping, and a 5 degree latitude-longitude grid, are mapped onto a computer- simulated globe to create this image. Data gaps are filled with Pioneer- Venus Orbiter data, or a constant mid-range value. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-39633 2/5/92 This global view of the surface of Venus is centered at 0 degrees east longitude. Magellan synthetic aperture radar mosaics from the first cycle of Magellan mapping, and a 5 degree latitude-longitude grid, are mapped onto a computer-simulated globe to create this image. Data gaps are filled with Pioneer-Venus Orbiter data, or a constant mid-range value. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-39634 2/5/92 This global view of the surface of Venus is centered at 90 degrees east longitude. Magellan synthetic aperture radar mosaics from the first cycle of Magellan mapping, and a 5 degree latitude-longitude grid, are mapped onto a computer-simulated globe to create this image. Data gaps are filled with Pioneer-Venus Orbiter data, or a constant mid-range value. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-39635 2/5/92 This global view of the surface of Venus is centered at 180 degrees east longitude. Magellan synthetic aperture radar mosaics from the first cycle of Magellan mapping, and a 5 degree latitude-longitude grid, are mapped onto a computer-simulated globe to create this image. Data gaps are filled with Pioneer-Venus Orbiter data, or a constant mid-range value. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-39636 2/5/92 This global view of the surface of Venus is centered at 270 degrees east longitude. Magellan synthetic aperture radar mosaics from the first cycle of Magellan mapping, and a 5 degree latitude-longitude grid, are mapped onto a computer-simulated globe to create this image. Data gaps are filled with Pioneer-Venus Orbiter data, or a constant mid-range value. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-39657bw MGN-88 January 27, 1992 This Magellan image shows a portion of Eistla Regio (Region) in the northern hemisphere of Venus, centered at 1 degrees south latitude, 37 degrees east longitude. The area is 440 kilometers (270 miles) wide and 350 kilometers (220 miles) long. This image was produced from Magellan radar data collected in Cycle Two of the mission. Cycle Two was completed January 15, 1992. The area was not imaged during the first cycle because of superior conjunction, when the Sun was between the Earth and Venus, preventing communication with the spacecraft. This image contains examples of several of the major geologic terrains on Venus and illustrates the basic stratigraphy or sequence of geologic events. The oldest terrains appear as bright, highly fractured or chaotic highlands rising out of the plains. This is seen in the right half of the image. The chaotic highlands, sometimes called tessera, may represent older and thicker crustal material and occupy about 15 percent of the surface of Venus. The fractured terrain in this region has a distinctly linear structure with a shear-like pattern. Plains surround and embay the fractured highland tessera. Plains are formed by fluid volcanic flows that may have once formed vast lava seas which covered all the low lying surfaces. Plains comprise more than 80 percent of the surface of Venus. The most recent activity in the region is volcanism that produced the radar bright flows best seen in the upper left quadrant of the image. The flows are similar, in their volcanic origin, to the darker plains volcanics, but apparently have more rugged surfaces that more efficiently scatter the radar signal back to the spacecraft. The geologic sequence is early fracturing of the tessera, flooding by extensive plains lavas, and scattered, less extensive individual flows on the plains surface. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-39657C MGN-88 January 27, 1992 This false color Magellan image shows a portion of Eistla Regio (Region) in the northern hemisphere of Venus, centered at 1 degrees south latitude, 37 degrees east longitude. The area is 440 kilometers (270 miles) wide and 350 kilometers (220 miles) long. This image was produced from Magellan radar data collected in Cycle Two of the mission. Cycle Two was completed January 15, 1992. The area was not imaged during the first cycle because of superior conjunction, when the Sun was between the Earth and Venus, preventing communication with the spacecraft. This image contains examples of several of the major geologic terrains on Venus and illustrates the basic stratigraphy or sequence of geologic events. The oldest terrains appear as bright, highly fractured or chaotic highlands rising out of the plains. This is seen in the right half of the image. The chaotic highlands, sometimes called tessera, may represent older and thicker crustal material and occupy about 15 percent of the surface of Venus. The fractured terrain in this region has a distinctly linear structure with a shear-like pattern. Plains surround and embay the fractured highland tessera. Plains are formed by fluid volcanic flows that may have once formed vast lava seas which covered all the low lying surfaces. Plains comprise more than 80 percent of the surface of Venus. The most recent activity in the region is volcanism that produced the radar bright flows best seen in the upper left quadrant of the image. The flows are similar, in their volcanic origin, to the darker plains volcanics, but apparently have more rugged surfaces that more efficiently scatter the radar signal back to the spacecraft. The geologic sequence is early fracturing of the tessera, flooding by extensive plains lavas, and scattered, less extensive individual flows on the plains surface. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-39658bw MGN-89 January 27, 1992 This Magellan image shows a portion of Bereghinya Planitia (plains) in the northern hemisphere of Venus, centered at 31 degrees north latitude, 43 degrees east longitude. The area is 260 kilometers (160 miles) wide and 330 kilometers (200 miles) long. This image was produced from Magellan radar data collected in Cycle Two of the mission. Cycle Two was completed January 15, 1992. The area was not imaged during the first cycle because of superior conjunction, when the Sun was between the Earth and Venus, preventing communication with the spacecraft. This image contains examples of several of the major geologic terrains on Venus and illustrates the basic stratigraphy or sequence of geologic events. The oldest terrains appear as bright, highly fractured or chaotic highlands rising out of the plains. This is seen in the upper right and lower left quadrants of the image. The chaotic highlands, sometimes called tessera, may represent older and thicker crustal material and occupy about 15 percent of the surface of Venus. Plains surround and embay the fractured highland tessera. Plains are formed by fluid volcanic flows that may have once formed vast lava seas which covered all the low lying surfaces. Plains comprise more than 80 percent of the surface of Venus. The most recent activity in the region is volcanism that produced the radar bright flows best seen in the lower right quadrant of the image. The lava flows in this image are associated with the shield volcano Tepev Mons whose summit is near the lower left corner of the image. The flows are similar to the darker plains volcanics, but apparently have more rugged surfaces that more efficiently scatter the radar signal back to the spacecraft. The geologic sequence is early fracturing of the tessera, flooding by extensive plains lavas, and scattered, less extensive individual flows on the plains surface. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-39658C MGN-89 January 27, 1992 This false color Magellan image shows a portion of Bereghinya Planitia (plains) in the northern hemisphere of Venus, centered at 31 degrees north latitude, 43 degrees east longitude. The area is 260 kilometers (160 miles) wide and 330 kilometers (200 miles) long. This image was produced from Magellan radar data collected in Cycle Two of the mission. Cycle Two was completed January 15, 1992. The area was not imaged during the first cycle because of superior conjunction, when the Sun was between the Earth and Venus, preventing communication with the spacecraft. This image contains examples of several of the major geologic terrains on Venus and illustrates the basic stratigraphy or sequence of geologic events. The oldest terrains appear as bright, highly fractured or chaotic highlands rising out of the plains. This is seen in the upper right and lower left quadrants of the image. The chaotic highlands, sometimes called tessera, may represent older and thicker crustal material and occupy about 15 percent of the surface of Venus. Plains surround and embay the fractured highland tessera. Plains are formed by fluid volcanic flows that may have once formed vast lava seas which covered all the low lying surfaces. Plains comprise more than 80 percent of the surface of Venus. The most recent activity in the region is volcanism that produced the radar bright flows best seen in the lower right quadrant of the image. The lava flows in this image are associated with the shield volcano Tepev Mons whose summit is near the lower left corner of the image. The flows are similar to the darker plains volcanics, but apparently have more rugged surfaces that more efficiently scatter the radar signal back to the spacecraft. The geologic sequence is early fracturing of the tessera, flooding by extensive plains lavas, and scattered, less extensive individual flows on the plains surface. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-39659bw MGN-90 January 27, 1992 This Magellan image shows a portion of Leda Planitia (plains) in the northern hemisphere of Venus, centered at 41 degrees north latitude, 52 degrees east longitude. The area is 220 kilometers (135 miles) wide and 275 kilometers (170 miles) long. This image was produced from Magellan radar data collected in Cycle Two of the mission. Cycle Two was completed January 15, 1992. The area was not imaged during the first cycle because of superior conjunction when the Sun was between the Earth and Venus, preventing communication with the spacecraft. This image contains examples of several of the major geologic terrains on Venus and illustrates the basic stratigraphy or sequence of geologic events. The oldest terrains appear as bright, highly fractured or chaotic highlands rising out of the plains. This is seen in the upper left, or northwest, quadrant of the image. The chaotic highlands, sometimes called tessera, may represent older and thicker crustal material and occupy about 15% of the surface of Venus. The circular ring structure in the lower left of the image is probably an impact crater. This 40 kilometer (25 mile) diameter crater has been given a proposed name Heloise, after the French physician who lived from about 1098 to 1164 A.D. The crater was formed by the impact of an asteroid sometime before the plains lavas embayed and covered the region. The plains surround and embay the fractured highland tessera. Plains are formed by fluid volcanic flows that may have once formed vast lava seas which covered all the low lying surfaces. Plains comprise more than 80 percent of the surface of Venus. The most recent activity in the region is volcanism that produced the radar bright flows best seen in the upper right quadrant of the image. Those flows are similar to the darker plains volcanics, but apparently have more rugged surfaces that more efficiently scatter the radar signal back to the spacecraft. Thus the geologic sequence is early fracturing of the tessera, flooding by extensive plains lavas, and scattered, less extensive individual flows on the plains surface. Impact cratering occurs throughout geologic history and provides a rough estimate of the time scale. Craters larger than a few kilometers in diameter form on Venus, as they do on Earth, at the rate of about one per million years, with smaller impacts much more frequent than larger ones. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-39659C MGN-90 January 27, 1992 This false color Magellan image shows a portion of Leda Planitia (plains) in the northern hemisphere of Venus, centered at 41 degrees north latitude, 52 degrees east longitude. The area is 220 kilometers (135 miles) wide and 275 kilometers (170 miles) long. This image was produced from Magellan radar data collected in Cycle Two of the mission. Cycle Two was completed January 15, 1992. The area was not imaged during the first cycle because of superior conjunction when the Sun was between the Earth and Venus, preventing communication with the spacecraft. This image contains examples of several of the major geologic terrains on Venus and illustrates the basic stratigraphy or sequence of geologic events. The oldest terrains appear as bright, highly fractured or chaotic highlands rising out of the plains. This is seen in the upper left, or northwest, quadrant of the image. The chaotic highlands, sometimes called tessera, may represent older and thicker crustal material and occupy about 15% of the surface of Venus. The circular ring structure in the lower left of the image is probably an impact crater. This 40 kilometer (25 mile) diameter crater has been given a proposed name Heloise, after the French physician who lived from about 1098 to 1164 A.D. The crater was formed by the impact of an asteroid sometime before the plains lavas embayed and covered the region. The plains surround and embay the fractured highland tessera. Plains are formed by fluid volcanic flows that may have once formed vast lava seas which covered all the low lying surfaces. Plains comprise more than 80 percent of the surface of Venus. The most recent activity in the region is volcanism that produced the radar bright flows best seen in the upper right quadrant of the image. Those flows are similar to the darker plains volcanics, but apparently have more rugged surfaces that more efficiently scatter the radar signal back to the spacecraft. Thus the geologic sequence is early fracturing of the tessera, flooding by extensive plains lavas, and scattered, less extensive individual flows on the plains surface. Impact cratering occurs throughout geologic history and provides a rough estimate of the time scale. Craters larger than a few kilometers in diameter form on Venus, as they do on Earth, at the rate of about one per million years, with smaller impacts much more frequent than larger ones. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. MAGELLAN PROJECT OFFICE P-39715 2/10/92 Maat Mons is displayed in this computer generated three-dimensional perspective view of the surface of Venus. The viewpoint is located 560 kilometers (347 miles) north of Maat Mons at an elevation of 1.7 kilometers (1 mile) above the terrain. Lava flows extend for hundreds of kilometers across the fractured plains shown in the foreground, to the base of Maat Mons. Maat Mons, an 8 kilometer (5 mile) high volcano, is located at approximately 0.9 degrees north latitude, 194.5 degrees east longitude. Maat Mons is named for an Egyptian Goddess of truth and justice. Magellan synthetic aperture radar data is combined with radar altimetry to develop a three-dimensional map of the surface. The vertical scale in this perspective has been exaggerated 22.5 times. Rays cast in a computer intersect the surface to create a three-dimensional perspective view. Simulated color and a digital elevation map developed by the U. S. Geological Survey, are used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-39716 2/10/92 This Magellan image is centered at 74.6 degrees north latitude and 177.3 east longitude, in the northeastern Atalanta Region of Venus. The image is approximately 185 kilometers (115 miles) wide at the base and shows Dickinson, an impact crater 69 kilometers (43 miles) in diameter. The crater is complex, characterized by a partial central ring and a floor flooded by radar-dark and radar-bright materials. Hummocky, rough-textured ejecta extend all around the crater, except to the west. The lack of ejecta to the west may indicate that the impactor that produced the crater was an oblique impact from the west. Extensive radar-bright flows that emanate from the crater's eastern walls may represent large volumes of impact melt, or they may be the result of volcanic material released from the subsurface during the cratering event. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-39717 2/10/92 This unusual Venusian volcano is located on the plains between Artemis Chasma and Imdr Regio at 37.5 degrees south and 164.5 degrees east. The most recent effusions of lavas produced the dome-like structure, about 100 kilometers (62 miles) across, with lava channels that radiate from the volcano's center. Lava flowing through one of these channels debouched on the plains to the lower-left of the volcano and produced a "lava-fan." The "dome" is about 0.5 to 1.0 kilometer (.3-.6 mile) high. Before the "dome" formed, lavas issued from the volcano and formed the extensive mesa of lavas above, to the right, and below the "dome." Lobes of lava along the margins of the mesa and the "dome," are near 60 meters (198 feet) thick; lava flows as thick as these are very rare on Venus. The concentric ridges and troughs on the flows are folds produced by compression of the cool upper surfaces of the lavas as they flowed. The earliest deposits are represented by the bright "fingers" at the upper- right and the bright lobes at the upper-left; dark patches at the lower- right are areas of non-deposition. These earliest deposits may have been produced by an explosive eruption of hot gases and lava fragments that generated pyroclastic flows. This volcano shows that magmatic differentiation has occurred on Venus - just as on our Earth. The differentiation produced an explosive eruption of a low-viscosity phase that generated pyroclastic flows and later effusions of high-viscosity phases of silica-rich lavas that produced the thick flows of the mesa and the dome-like structure. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-39838, P-39839, P-39840 3/10/92 These three images (P-39840, P-39839, P-39838) illustrate the range in regional coverage and resolution available in three of the standard Magellan image data products. The first image, (P-39840), is a C2-MIDR (Compressed-twice Mosaicked Image Data Record) centered at 30 degrees north latitude, 335 degrees east longitude, in the southern Sedna Planitia region of Venus. The mosaic covers an area of approximately 27 million square kilometers, with a pixel spacing of 675 meters, enabling planetary scientists to characterize the relationships of relatively large-scale structures on the planet. Two large volcanoes - Sif Mons and Gula Mons - can be seen below center right. Numerous radar-bright lava flows radiate from the summit calderas of these volcanoes. The second mosaic, (P-39839), is a C1-MIDR (Compressed-once Mosaicked Image Data Record) of the region at right center of the first image, centered at 30 degrees north latitude, 350 degrees east longitude. This image covers an area of approximately 3 million square kilometers with a pixel spacing of 225 meters, and shows three times as much detail visible in the first mosaic. This scale is most suited to the study of medium-scale structures, such as the radar-dark streak below center. The third mosaic, (P-39838), is a full-resolution mosaic centered at 25 degrees north latitude, 357 degrees east longitude. It covers an area of approximately 350,000 square kilometers, with a pixel spacing of 75 meters. This scale allows planetary scientists to examine small-scale structures in detail, including superposition relationships between lava flows and surrounding plains, and cross-cutting relationships between sets of fault troughs or ridges. The irregular circular feature or corona in the right center of the image is a low dome approximately 100 kilometers (62 miles) in diameter. The corona is flanked by two major lava flows that extend downslope to the north for several hundred kilometers. The entire region lies on the northern flank of a broad regional highland that contains the two volcanic centers of Sif Mons and Gula Mons. The dark streak in the upper left of the image is associated with two small impact craters. The object that formed the craters appears to have broken up during its passage through the dense Venusian atmosphere. Radar-dark streaks associated with small impact craters may form from the interaction between an intense shock wave and the surface, or as a result of deposition of fine-grained ejecta. The radar- dark surface is apparently smoother than its surroundings. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-39916 MGN-93 March 16, 1992 This unusual Venusian volcano is located on the plains between Artemis Chasma and Imdr Regio at 37.5 degrees south latitude and 164.5 degrees east longitude. The dome structure with lava channels radiating from the volcanic center is about 100 km (62 miles) across. This volcanic feature has been imaged by Magellan in both left-looking and right-looking modes. This image, from the second mapping cycle, was taken from the right. The volcano and its lava flows appear much the same in both images, but there are two important differences. In the left-looking image west-facing slopes are brighter because they are tilted toward the radar. In this right-looking image, west-facing slopes are darker because they face away from the radar. Another difference is the image displacement caused by elevation differences as seen by the radar from the two sides. The top of a flow margin is displaced toward the radar relative to its base. The displacement is in the opposite direction in the two images. The sum of the two displacements is called parallax and can be used to estimate the height of features. The topographic relief that can be measured horizontally is much more precise than can be measured with the altimeter (about 10 kilometers, or 6 miles). Parallax measurements show that the thickness of the lobe of lava at the left-center edges of the image is variable but typically about 540 meters (1772 feet). This measurement conflicts with the altimetry measurement. The fan-shaped lava flow in the lower left is about 120 meters (394 feet) thick near its edge. Lava scarps on the east side of the complex are about 90 meters (295 feet) high. (See P-39717) PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-40030 MGN-94 March 30, 1992 As the Magellan mission has progressed, areas of Venus have become accessible to the imaging radar system for a second look. During Magellan's second 243-day global mapping cycle, the spacecraft was rotated 180 degrees to view the surface from the opposite direction. This pair of mosaics shows a region of Venus 575 kilometer (356 miles) by 460 kilometers (285 miles) as viewed in March 1991 from the left or west (top image) and in November 1991 from the right or east (bottom image). This image is centered at approximately 48 degrees south latitude, 230 degrees east longitude in the Imdr region of Venus. The incidence angle of the radar beam with the surface for both observations was approximately 25 degrees from vertical. The dark band near the right edge of the March image is due to a missing segment of data from one orbit. Much of the surface appears different in the two observations. Some of the darkest areas in the top image appear patchy and bright in the bottom image. In addition, east-west trending, alternating bright and dark bands in the lower left part of the bottom image are nearly or completely invisible in the top image. Magellan scientists are currently evaluating these apparent differences to understand their origin. Two theories have been developed. In one interpretation, the bright patches in the November (bottom) image are reflections from facets of surface material that are oriented toward the east with a slope of approximately 25 degrees. This would lead to strong mirror-type reflections that are only visible from the east, the direction from which the surface was viewed in November. Under the second interpretation, the surface itself is proposed to have changed between image acquisitions. It is suggested that materials on the surface had been rearranged sometime during the 8-month period, possibly by near-surface winds. Under this interpretation, the apparent brightening of the surface is explained as a result of the removal of loose material such as dust or sand, exposing a rougher, rockier surface that would appear brighter in a radar image. Magellan scientists hope to obtain a third view of this area in July 1992, under a viewing geometry similar to the earlier data. This should provide the information necessary to distinguish between the "viewing direction" and "surface change" interpretations. MAGELLAN PROJECT OFFICE P-40049 4/2/92 This Magellan image, centered at 60 degrees north latitude, 355 degrees east longitude, is 610 kilometers (378 miles) long by 540 kilometers (335 miles) wide. At the top of this Magellan full resolution mosaic (F-MIDR) the elevated plateau Lakshmi Planum drops off from a height of 4 kilometers (2.5 miles) into deformed lava plains which reside at or near the mean elevation of Venus. Intertwining wrinkle ridges, which have bright west facing slopes are present throughout most of the southern and eastern half of the image. Subtle differences in brightness may be attributed to the roughness of different lava flows (with the bright areas being the roughest). The bright, irregular lines in the top left of the image are fractures which may have formed from the elevated area collapsing under its own weight due to the flexibility of rock at the hot Venusian surface temperatures. The egg-shaped feature in the upper right portion of the image is a volcanic caldera, 40 kilometers (25 miles) long along its major axis. Such features form when lava is extruded from a subsurface chamber which subsequently collapses leaving a large depression on the surface. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-40142AC 12/1/92 These images present the topography of Venus obtained by the Magellan radar altimeter, using color to code (see color bar) elevation, and simulated shading to emphasize relief. Red corresponds to the highest, blue to the lowest elevations. The upper image shows that part of the planet between 69 degrees north and 69 degrees south latitude in Mercator projection; beneath it are the two polar regions covering latitudes above 44 degrees in stereographic projection. Easterly longitudes run across the Mercator map from left to right, and around the periphery of the polar stereographic projections. Height accuracy is better than 50 meters; horizontal ("footprint") resolution of the surface depends on spacecraft altitude, being about 10 kilometers near the equator and degrading to as much as 25 kilometers at high latitudes. Gray areas show the coarser results from the 1978 Pioneer Venus mission, and indicate where data had not yet been obtained by Magellan after the first eight months of operation. The elevated region in the north is Ishtar Terra, dominated by Maxwell Montes (the planet's highest mountains) which rise 11 kilometers (36,000 feet) above the planetary mean. The scorpion-shaped feature extending along the equator between 70 and 210 degrees longitude is Aphrodite Terra, a zone that contains several spectacular volcanoes at its eastern limit: Maat, Ozza and Sapas Montes. Major geologic feature names are indicated on the top image. The altimetric data shown here were analyzed and projected at the Center for Space Research, Massachusetts Institute of Technology. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-40144 5/4/92 These images display the meter-scale roughness of the Venus surface (characterized by its root-mean-square average slope), as observed by the Magellan radar altimeter. The lightest shades locate areas having the steepest values of average slope, while darker shades indicate areas that are smoother. The upper image shows that part of the planet between 69 degrees north and 69 degrees south latitude in Mercator projection; beneath it are the two polar regions covering latitudes above 44 degrees in stereographic projection. Easterly longitudes run across the Mercator map from left to right, and around the periphery of the polar stereographic projections. Resolution of the surface varies with spacecraft altitude, being about 10 kilometers near the equator and degrading to as much as 25 kilometers at high latitudes. Black areas indicate where data had not yet been obtained by Magellan after the first eight months of operation. There is a tendency for elevated regions, e.g. the Maxwell Montes (left of the data gap at top center) and Aphrodite Terra (along the equator at right), to show steeper meter-scale slopes than are typical of lower-lying areas. The steeper slopes probably result from disruption of the surface associated with tectonic activity in these regions. Note the large 2300- kilometer (1400-mile) diameter circular feature (Artemis Chasma) in the lower right of the Mercator image. This feature is thought to have been caused by a gigantic plume of heated rock rising from the planet's interior. The data shown here were analyzed and projected at the Center for Space Research, Massachusetts Institute of Technology. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-40156 MGN-95 April 22, 1992 Impact craters on Venus have been shown by Magellan radar data to have properties unlike craters on any other planet in the solar system. As the mission has progressed, many areas of the planet, including some containing unusual crater-related deposits, have become accessible for a second look. During the second 243-day global mapping cycle, the spacecraft was rotated 180 degrees to view the surface from the opposite side. This pair of mosaics shows a region of Venus 860 kilometers by 700 kilometers (515 miles by 420 miles), as viewed in February, 1991 from the left or west (top image) and in October, 1991 from the right or east (bottom image). The image is centered at approximately 58 degrees south latitude, 200 degrees east longitude, in the Imdr region of Venus. Black strips in the top image are due to missing data. The incidence angle of the radar beam with the surface was approximately 21 degrees from vertical in the top image, and 24 degrees from vertical in the bottom image. The 29 kilometer (17.5 mile) diameter crater near the center of the image has provisionally been named Eudocia, for the 5th century Byzantine empress. Much of the surface surrounding the crater appears different in the two observations. Many patchy bright areas in the top image appear dark in the bottom image. In addition, alternating bright and dark bands in the top image are nearly or completely invisible in the bottom image. These areas are part of a large parabolic-shaped feature associated with Eudocia. Magellan scientists are currently evaluating these apparent differences to understand their origin. The bright patches are clearly related to features on the surface, ruling out an atmospheric source. Two theories have been developed to explain the observed differences. In one interpretation, the bright patches in the February (top) image are reflections from facets of surface material that are oriented toward the west with a slope of approximately 21 degrees. This would lead to strong mirror-type reflections that are only visible from the west, the direction from which the surface was viewed in February. These facets may be slopes of small dunes or ripple structures formed by the wind. Under the second interpretation, the surface itself is proposed to have changed between image acquisitions. It is suggested that materials on the surface have been rearranged sometime during the 8-month period, possibly by near-surface winds. Under this interpretation, the apparent darkening of the surface is explained as a result of the deposition of loose material such as dust or sand, covering a rougher, rockier surface that appears brighter in the earlier image. JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-40157 MGN-96 April 22, 1992 Impact craters on Venus have been shown by Magellan radar data to have properties unlike craters on any other planet in the solar system. As the mission has progressed, many areas of the planet, including some containing unusual crater-related deposits, have become accessible for a second look. During the second 243-day global mapping cycle, the spacecraft was rotated 180 degrees to view the surface from the opposite side. This pair of mosaics shows a region of Venus 860 kilometers by 700 kilometers (515 miles by 420 miles), as viewed in January, 1991 from the left or west (top image) and in October, 1991 from the right or east (bottom image). The image is centered at approximately 61 degrees south latitude, 184 degrees east longitude, in the Imdr region of Venus. The black strip across the top image is due to a missing orbit. The incidence angle of the radar beam with the surface was approximately 20 degrees from vertical in the top image, and 24 degrees from vertical in the bottom image. A 45 kilometer (27 mile) diameter crater, provisionally been named Kuan Tao-Sheng for the 13th century Chinese painter and calligrapher is seen near the center of the image, along with a 30 kilometer (18 mile) diameter unnamed crater to the northwest. Much of the surface surrounding the craters appears different in the two observations. Many patchy bright areas in the top image appear dark in the bottom image, while other areas are bright only in the bottom image. These areas are part of a large parabolic-shaped feature associated with the craters. Magellan scientists are currently evaluating these apparent differences to understand their origin. Two theories have been developed to explain the observed differences. In one interpretation, the bright patches in the January (top) image are reflections from facets of surface material that are oriented toward the west with a slope of approximately 20 degrees. This would lead to strong mirror-type reflections that are only visible from the west, the direction from which the surface was viewed in January. Similar structures having slopes near 24 degrees to the east could occur in the areas that appear bright only in the October image. These facets may be slopes of small dunes or ripple structures formed by the wind. Under the second interpretation, the surface itself is proposed to have changed between image acquisitions. It is suggested that materials on the surface have been rearranged sometime during the 8 and 1/2 month period, possibly by near-surface winds. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109. (818) 354-5011 PHOTO CAPTION MAGELLAN P-40158 April 22, 1992 This Magellan full-resolution mosaicked anaglyph centered at 69.5 degrees north latitude, 355 degrees east longitude covers an area approximately 375 by 450 kilometers (233 by 115 miles), located north of the 10 kilometer high (6.2 mile) mountain belt called Maxwell Montes. An anaglyph is a type of image consisting of two data sets which are slightly displaced from one, another and projected in red and blue so that a 3-dimensional or stereo effect is produced when the image is viewed through red and blue tinted glasses. The images were obtained when Magellan "looked" at the same part of the surface from different angles during its first and third mapping cycles (October 1990 and February 1992, respectively). The ability to see both the radar image and differences in elevation together is valuable for geologic interpretation. The image is dominated by volcanic plains (the radar-dark or smooth areas) and tessera (the rough contorted terrain which is unique to Venus). The radar-bright terrain at the bottom right of the image is believed to be an unusual mineral alteration covering most of Maxwell Montes. Slightly north of this are large, dome-shaped areas whose morphologies are not visible in the 2-dimensional radar images. The image was produced at the JPL Multimission Image Processing Laboratory. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109. (818) 354-5011 PHOTO CAPTION MAGELLAN P-40159 April 22, 1992 This Magellan full-resolution mosaicked anaglyph centered at 66.5 degrees north latitude, 0.0 degrees east longitude covers an area approximately 300 by 300 kilometers (186 by 186 miles) at the northern end of Maxwell Montes, the tallest mountain belt on Venus at approximately 10 kilometers (6.2 miles) above the average elevation on the planet. An anaglyph is a type of image consisting of two data sets slightly displaced from one another and projected in red and blue so that a 3-dimensional or stereo effect is produced when the image is viewed through red and blue tinted glasses. The images were obtained when Magellan "looked" at the same part of the surface from different incidence angles during its first and third mapping cycles (October 1990 and February 1992, respectively). The ability to see both the radar image and differences in elevation together is valuable for geologic interpretation. The two broad valleys, crossing through the center of the image are not visible in the 2-dimensional radar images. Likewise, the image reveals that Maxwell Montes, which trends approximately northwest is cut by northeast trending mountains in the upper, left portion of the image, indicating that the latter are younger. It is also apparent from this image that the anomalously bright terrain which scientists are attempting to understand does not occur at or greater than a specific elevation although it generally occurs at high altitudes. The image was produced at the JPL Multimission Image Processing Laboratory. MAGELLAN PROJECT OFFICE P-40160 5/4/92 This Magellan full-resolution mosaicked anaglyph centered at 65 degrees north latitude, 0.0 degrees east longitude covers an area approximately 614 by 537 kilometers (381 by 333 miles) where the smooth, elevated plains of Lakshmi Planum (on the left portion of the image) meet Maxwell Montes, the tallest mountain belt on Venus at approximately 10 kilometers (6.2 miles) above the average elevation on the planet. An anaglyph is a type of image consisting of two data sets slightly displaced from one another and projected in red and blue so that a 3-dimensional or stereo effect is produced when the image is viewed through red and blue tinted glasses. The images were obtained when Magellan "looked" at the same part of the surface from different incidence angles during its first and third mapping cycles (October 1990 and February 1992, respectively). The ability to see both the radar image and differences in elevation together is valuable for geologic interpretation. The broad valleys, in the upper, center portion of the image are not visible in the 2-dimensional radar images. Likewise, the image reveals that Maxwell Montes, which trends approximately northwest is cut by northeast trending mountains in the top, left portion of the image, indicating that the latter are younger. It is also apparent from this image that the anomalously bright terrain which scientists are attempting to understand does not occur at or greater than one specific "cutoff" elevation although it generally occurs at high altitudes. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109 PHOTO CAPTION MAGELLAN P-40175 MGN-97 April 22, 1992 Maat Mons is displayed in this computer generated three-dimensional perspective view of the surface of Venus. The viewpoint is located 634 kilometers (393 miles) north of Maat Mons at an elevation of 3 kilometers (2 miles) above the terrain. Lava flows extend for hundreds of kilometers across the fractured plains shown in the foreground, to the base of Maat Mons. The view is to the south with the volcano Maat Mons appearing at the center of the image on the horizon and rising to almost 5 kilometers (3 miles) above the surrounding terrain. Maat Mons, is located at approximately 0.9 degrees north latitude, 194.5 degrees east longitude with a peak that ascends to 8 kilometers (5 miles) above the mean surface. Maat Mons is named for an Egyptian Goddess of truth and justice. Magellan synthetic aperture radar data is combined with radar altimetry to develop a three-dimensional map of the surface. The vertical scale in this perspective has been exaggerated 10 times. Rays cast in a computer intersect the surface to create a three-dimensional perspective view. Simulated color and a digital elevation map developed by the U. S. Geological Survey, are used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory and is a single frame from a video released at the April 22, 1992 news conference. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109. (818) 354-5011 PHOTO CAPTION MAGELLAN P-40176 MGN-98 April 22, 1992 Sapas Mons is displayed in the center of this computer-generated three- dimensional perspective view of the surface of Venus. The viewpoint is located 527 kilometers (327 miles) northwest of Sapas Mons at an elevation of 4 kilometers (2.5 miles) above the terrain. Lava flows extend for hundreds of kilometers across the fractured plains shown in the foreground to the base of Sapas Mons. The view is to the southeast with Sapas Mons appearing at the center with Maat Mons located in the background on the horizon. Sapas Mons, a volcano 400 kilometers (248 miles) across and 1.5 kilometers (0.9 mile) high is located at approximately 8 degrees north latitude, 188 degrees east longitude, on the western edge of Atla Regio. Its peak sits at an elevation of 4.5 kilometers (2.8 miles) above the planet's mean elevation. Sapas Mons is named for a Phoenician Goddess. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The vertical scale in this perspective has been exaggerated 10 times. Rays cast in a computer intersect the surface to create a three-dimensional perspective view. Simulated color and a digital elevation map developed by the U. S. Geological Survey, are used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory and is a single frame from a video released at the April 22, 1992 news conference. MAGELLAN PROJECT OFFICE P-40255 6/1/92 Maat Mons is displayed in this computer generated three-dimensional perspective view of the surface of Venus. This image was created on Caltech's Intel Touchstone Delta Supercomputer. The viewpoint is located 634 kilometers (393 miles) north of Maat Mons at an elevation of 3 kilometers (2 miles) above the terrain. Lava flows extend for hundreds of kilometers across the fractured plains shown in the foreground, to the base of Maat Mons. The view is to the south with the volcano Maat Mons appearing at the center of the image on the horizon and rising to almost 5 kilometers (3 miles) above the surrounding terrain. Maat Mons is located at approximately 0.9 degrees north latitude, 194.5 degrees east longitude with a peak that ascends to 8 kilometers (5 miles) above the mean surface. Maat Mons is named for an Egyptian Goddess of truth and justice. Magellan synthetic aperture radar data is combined with radar altimetry to develop a three-dimensional map of the surface. The vertical scale in this perspective has been exaggerated 10 times. Rays cast in a computer intersect the surface to create a three-dimensional perspective view. Simulated color and a digital elevation map developed by the U.S. Geological Survey are used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan Science Team at the JPL Multimission Image Processing Laboratory and is a single frame from a video being created on the Delta Supercomputer. This work is part of NASA's "Grand Challenge" research effort in the planetary science applications of high performance computers. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-40256 6/1/92 Sapas Mons is displayed in the center of this computer-generated three- dimensional perspective view of the surface of Venus. This image was created on Caltech's Intel Touchstone Delta Supercomputer. The viewpoint is located 527 kilometers (327 miles) northwest of Sapas Mons at an elevation of 4 kilometers (2.5 miles) above the terrain. Lava flows extend for hundreds of kilometers across the fractured plains shown in the foreground to the base of Sapas Mons. The view is to the southeast with Sapas Mons appearing at the center with Maat Mons located in the background on the horizon. Sapas Mons, a volcano 400 kilometers (248 miles) across and 1.5 kilometers (0.9 miles) high is located at approximately 8 degrees north latitude, 188 degrees east longitude, on the western edge of Atla Regio. Its peak sits at an elevation of 4.5 kilometers (2.8 miles) above the planet's mean elevation. Sapas Mons is named for a Phoenician goddess. The vertical scale in this perspective has been exaggerated 10 times. Rays cast in a computer intersect the surface to create a three-dimensional perspective view. Simulated color and a digital elevation map developed by the U.S. Geological Survey are used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan Science Team at the JPL Multimission Image Processing Laboratory and is a single frame from a video being created on the Delta Supercomputer. This work is part of NASA's "Grand Challenge" research effort in the planetary science applications of high performance computers. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-40257 6/1/92 Sapas Mons is displayed in this computer generated three-dimensional perspective view of the surface of Venus. This image was created on Caltech's Intel Touchstone Delta Supercomputer. The viewpoint is located 243 kilometers (151 miles) south of Sapas Mons. Lava flows extend for hundreds of kilometers from the large volcano into the smooth plains. The view is to the north with the volcano Sapas Mons appearing at the center of the image at approximately 0.9 degrees north latitude, 188 degrees east longitude with two peaks that ascend to 3 kilometers (1.8 miles) above the mean surface. Sapas Mons is named after an ancient Phoenician Goddess. Magellan synthetic aperture radar data is combined with radar altimetry to develop a three-dimensional map of the surface. The vertical scale in this perspective has been exaggerated 10 times. Rays cast in a computer intersect the surface to create a three-dimensional perspective view. Simulated color and a digital elevation map developed by the U.S. Geological Survey are used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan Science Team at the JPL Multimission Image Processing Laboratory and is a single frame from a video being created on the Delta Supercomputer. This work is part of NASA's "Grand Challenge" research effort in the planetary science applications of high performance computers. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-40258 6/1/92 The great volcanos of Atla Regio, Sapas, Maat and Ozza Montes are displayed in this computer generated three-dimensional perspective view of the surface of Venus. This image was created on Caltech's Intel Touchstone Delta Supercomputer. The viewpoint is located on the flank of Sapas Mons, 1216 kilometers (754 miles) northwest of Maat Mons, which is in the center of the image on the horizon, towering above the plains at an elevation of 8 kilometers (5 miles). Lava flows extend for hundreds of kilometers across the smooth plains from the margins of the volcanoes. The view is to the southeast with Maat Mons located at approximately 0.9 degrees north latitude, 194.5 degrees east longitude and Sapas at 9 degrees north latitude, 188 degrees east longitude. Sapas Mons is named after an ancient Phoenician goddess, while the name Maat comes from an Egyptian Goddess of truth and justice. Magellan synthetic aperture radar data is combined with radar altimetry to develop a three-dimensional map of the surface. The vertical scale in this perspective has been exaggerated 10 times. Rays cast in a computer intersect the surface to create a three-dimensional perspective view. Simulated color and a digital elevation map developed by the U.S. Geological Survey are used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan Science Team at the JPL Multimission Image Processing Laboratory and is a single frame from a video being created on the Delta Supercomputer. This work is part of NASA's "Grand Challenge" research effort in the planetary science applications of high performance computers. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIFORNIA 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-40286 MGN-99 May 29, 1992 This image, with radar illumination from west to east, shows three unusual volcanoes located in the Guinevere Planitia lowland. At the center of the image is a large feature (50 kilometers or 31 miles in diameter) with an unusual shape: very round when viewed from above with steep-sides and a flat top. These volcanoes are believed to be the result of relatively thick and sticky (viscous) lava flows that originated from a point source. Although a faint remnant of its original circular shape is preserved, the northern rim of this central volcano has a steep scarp. The scarp is probably the result of material that has slid away from the volcano and subsequently has been covered by lava flows. This volcano overlaps another feature to the southwest that is about 45 kilometers (28 miles) in diameter and disrupted by many fractures. The southeastern volcano (25 kilometers or 15.5 miles in diameter) appears to be the highest of the three as its illuminated western edge has the brightest radar return. The scalloped edges give this feature a bottle-cap like appearance. The highly scalloped edges are probably the result of multiple material slides along the volcano margin. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIFORNIA 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-40287 MGN-100 May 29, 1992 The Magellan spacecraft has observed remnant landslide deposits apparently resulting from the collapse of volcanic structures. This Magellan radar image is centered about 25.4 degrees south latitude and 308 degrees east longitude in the Southwestern Navka Region of Venus. The image shows a 17.4 kilometer (10.8 mile) diameter volcanic dome on the plains. The dome is approximately 1.86 kilometers (1.2 mile) in height and it has a slope of about 23 degrees. The northwest and northeast flanks of the dome have collapsed to form landslides that have deposited debris on the plains. The image shows an area 110 kilometers (68 miles) across and 100 kilometer (62 miles) in length. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIFORNIA 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-40288 MGN-101 May 29, 1992 The Magellan spacecraft has observed remnant landslide deposits apparently resulting from the collapse of volcanic structures. This image, centered at 45.2 degrees south latitude, 201.4 degrees east longitude, shows a collapse deposit 70 kilometers (43 miles) across. The bright, highly textured deposit near the center of the image probably consists of huge blocks of fractured volcanic rock, many as large as several hundred meters across. A remnant of the volcano itself, about 20 kilometers (12.4 miles) across, is seen at the center of the image. The distorted radar appearance of the volcano is a result of extremely steep slopes on the "scars" from which the landslide material originated. A field of numerous small volcanic domes can be seen in the northern half of the image. The bright irregular lineaments trending to the north-northwest are ridges caused by regional tectonic deformation of the upper layers of the Venusian crust. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIFORNIA 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-40289 MGN-102 May 29, 1992 This Magellan full-resolution mosaic which covers an area 143 by 146 kilometers (89 by 91 miles) is centered at 55 degrees north latitude, 266 degrees east longitude. The bright feature, slightly south of center is interpreted to be a volcano, 15-20 kilometers (9.3 to 12.4 miles) in diameter with a large apron of blocky debris to its right and some smaller aprons to its left. A preferred explanation is that several massive, catastrophic landslides dropped down steep slopes and were carried by their momentum out into the smooth, dark lava plains. At the base of the east- facing or largest scallop on the volcano is what appears to be a large block of coherent rock, 8-10 kilometers (5 to 6 miles) in length. The similar margin of both the scallop and block and the shape in general is typical of terrestrial slumped blocks (masses of rock which slide and rotate down a slope instead of breaking apart and tumbling). The bright lobe to the south of the volcano may either be a lava flow or finer debris from other landslides. This volcanic feature, characterized by its scalloped flanks is part of a class of volcanos called scalloped or collapsed domes of which there are more than 80 on Venus. Based on the chute-like shapes of the scallops and the existence of a spectrum of intermediate to well defined examples, it is hypothesized that all of the scallops are remnants of landslides even though the landslide debris is often not visible. Possible explanations for the missing debris are that it may have been covered by lava flows, the debris may have weathered or that the radar may not be recognizing it either because the individual blocks are too small. MAGELLAN PROJECT OFFICE P-40333 6/1/92 Hyppolyta Linea, a system of surface fractures in the Lavinia region of Venus, is shown in this false-color Magellan radar image. The area pictured is 325 kilometers by 360 kilometers (202 miles by 223 miles) and is centered at 41 degrees south latitude, 340 degrees east longitude. The fracture belt sits somewhat higher in elevation (about 1 kilometer or 0.62 mile) than the surrounding volcanic plains, and is dominated by sets of fault-bounded valleys known as graben. The trend of most of these fractures is perpendicular to sets of narrow sinuous features called "wrinkle ridges" that are seen in the plains at the top and bottom of the image. Similar wrinkle ridges have been identified on the surfaces of the Moon, Mars and Mercury. They are believed to be the result of horizontal compressional forces in the uppermost layers of the planets' crusts. The inter-relationships between the compression-related wrinkle ridges and the likely extension-related graben structures allow geologists to unravel the tectonic history of this region of the surface of Venus. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-40347 6/15/92 These images display the distribution of radio-thermal emission efficiency (emissivity) over the Venus surface, observed using the Magellan SAR radar receiver. Color is used to code the emission efficiency (see color bar). Red corresponds to the highest, blue to the lowest values of emissivity. The upper image shows that part of the planet between 69 degrees north and 69 degrees south latitude in Mercator projection; beneath it are the two polar regions covering latitudes above 44 degrees in stereographic projection. Easterly longitudes run across the Mercator map from left to right, and around the periphery of the polar stereographic projections. The emissivity of the surface is determined primarily by its bulk electrical properties and on the angle at which the emitted radiation is viewed. The decrease in average emissivity at low latitudes results from the higher view angle there. The horizontal resolution also varies with latitude, being determined solely by the "footprint" of Magellan's high- gain SAR antenna beam. Near the equator the surface resolution is about 20 kilometers, but at high latitudes it degrades to as much as 100 kilometers. There is a tendency for elevated regions, e.g. the Maxwell Montes (left of the data gap at top left center) and Aphrodite Terra (along the equator at right center), to show lower values of emissivity than are typical of lower-lying areas. These low values confirm the high values of radar reflectivity seen in corresponding regions by the Magellan altimeter, but do not offer significant additional information to help solve the considerable puzzle of what mechanism may underlie this unexpected behavior. On a cooler planet such as Earth or Mars, water or ice might explain the anomalous observations, but at the 470-degree-Celsius temperature of the Venus surface, neither can be present. Some theories require the presence of minerals such as iron pyrites; others suggest a material, as yet unidentified, that has extremely low electrical loss. The data shown here were analyzed and projected at the Center for Space Research, Massachusetts Institute of Technology. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-40348 6/15/92 These images show the distribution of radar reflection coefficient (reflecting efficiency) of the Venus surface when viewed from directly overhead by the Magellan altimeter. The lightest shades locate areas having the highest values of normal-incidence reflectivity (as high as 70 percent in places), while darker shades indicate areas of low reflection efficiency. The upper image shows that part of the planet between 69 degrees north and 69 degrees south latitude in Mercator projection; beneath it are the two polar regions covering latitudes above 44 degrees in stereographic projection. Easterly longitudes run across the Mercator map from left to right, and around the periphery of the polar stereographic projections. Resolution of the surface varies with spacecraft altitude, being about 10 kilometers near the equator and degrading to as much as 25 kilometers at high latitudes. Black areas indicate where data had not yet been obtained by Magellan after the first eight months of operation. There is a tendency for elevated regions, e.g. the Maxwell Montes (left of the data gap at top center) and Aphrodite Terra (along the equator at right), to show higher values of reflectivity than are typical of lower- lying areas. The highest values (greater than 30 percent) are puzzling to understand. On a cooler planet such as Earth or Mars, water or ice might explain the observations, but at the 470-degree-Celsius temperature of the Venus surface, neither can be present. Some theories require the presence of minerals such as iron pyrites; others suggest a material, as yet unidentified, that has extremely low electrical loss. The data shown here were analyzed and projected at the Center for Space Research, Massachusetts Institute of Technology. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-40657 7/22/92 This Magellan synthetic aperture radar (SAR) mosaic is a sinusoidal equal- area projection of Venus. Centered at 180 degrees latitude, the image includes all information gathered by the spacecraft from the beginning of the mission in September, 1990 through July, 1991. A sinusoidal equal-area projection distorts the true shapes of features while allowing an unbiased view of the sizes of features whether they are on the equator or near the poles. While the planet rotates underneath the spacecraft, Magellan collects successive swaths of data, approximately 25 kilometers (16 miles) in width but tens of thousands of kilometers or miles in length. After Venus has rotated one full Venusian day or 243 Earth days, the spacecraft completes its passage over the entire surface. Represented in this image is the sum total of the information from Magellan's 'first passage' referred to as 'Cycle 1,' along with one major gap fill from Cycle 2. The solid black regions are gaps in the data set primarily due to spacecraft and/or planetary geometry constraints. For example, we could not receive information from Magellan during Superior Conjunction, when the spacecraft was on the other side of the Sun from the Earth. This image was produced by Washington University, St. Louis, Missouri. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 PUBLIC INFORMATION OFFICE Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-40686 (B,C) MGN-103 August 11, 1992 This Magellan full-resolution mosaic of Venus, centered at 10 degrees north latitude, 301 degrees east longitude shows an area replete with diverse volcanic features. The image of an area 489 kilometers long by 311 kilometers wide (303 by 193 miles), is dominated by volcanic plains which appear mottled because of varying roughnesses of each solidified lava flow. The rougher the terrain the brighter it appears in the radar image. The small, bright bumps clustered in the left portion of the image are a grouping of small volcanoes called a shield field. Each shield volcano is approximately 2 to 5 kilometers (1.2 to 3.1 miles) in diameter and has very subdued relief. It is believed that the lava flows that make up each shield originates from a common source. To the right of the shield field is another type of volcano called a scalloped dome. It is 25 kilometers (16 miles) in diameter and has a central pit. Some of the indistinct lobe- shaped pattern around the dome may either be lava flows or rocky debris which has fallen from the scalloped cliffs surrounding the domes. The small radial ridges characteristic of scalloped domes are remnants of catastrophic landslides. To the right of that feature is a large depression called a volcanic caldera. The caldera was formed when lava was expelled from an underground chamber, which when emptied, subsequently collapsed, forming the depression. The feature furthest to the east (right) is another scalloped dome, 35 kilometers (22 miles). That feature is unusual in that lava came out through the southeastern margin, rafting a large portion of the dome for 20 kilometers (12 miles). The lava continues into the lower right portion of the area in the image. Its steep rounded boundaries suggest it was a very sticky, oozing lava. That same type of lava is what scientists propose formed the steep-sided domes such as the bright, round feature, slightly northeast of center. It is highly likely that the features are all part of a single volcanic complex, where a large body of molten rock formed beneath the surface feeding each of the volcanoes above. The presence of fractures in the west, partially surrounding the volcanoes supports this theory. PUBLIC INFORMATION OFFICE Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-40690 MGN-104 August 11, 1992 This full resolution Magellan radar mosaic centered at 14 degrees north latitude, 72 degrees east longitude, shows an oblique view of the impact crater Riley, named for Margaretta Riley, a 19th century botanist. This view was prepared from two left-looking Magellan radar images acquired with different incidence angles. Because the relief displacements on the two images are different, depths from the crater rim to the crater floor and heights of the crater rim and flanks above the surrounding plains can be measured. The crater is 25 kilometers (15.5 miles) in diameter. The floor of the crater is 580 meters (1914 feet) below the plains surrounding the crater. The crater's rim rises 620 meters (2046 feet) above the plains and 1200 meters (3960 feet) above the crater floor. The crater's central peak is 536 meters (1769 feet) tall. The crater's diameter is 40 times the depth resulting in a relatively shallow appearance. The topography is exaggerated by 22 times to emphasize the crater's features. This oblique view was produced from two left-looking radar stereo image mosaics utilizing photogrammetric software developed by the Solar System Visualization Project and the Digital Image Animation Laboratory at the Jet Propulsion Laboratory's Multimission Image Processing Laboratory. PUBLIC INFORMATION OFFICE Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-40691 MGN-105 August 11, 1992 This set of three Magellan images shows a small volcano, lava plains distorted into "wrinkle ridges," and some unusual wispy-appearing surface deposits. The images were acquired during the first, second, and third mapping cycles of the mission, in March,1991, November 1991, and July 1992, respectively. The area shown is about 400 kilometers by 100 kilometers (248 miles by 62 miles) and is centered near 47.5 degrees south latitude, 226 degrees east longitude, in the Imdr region of Venus. The middle image, from the second cycle, was acquired with the spacecraft facing toward the west (left), while the other two images were acquired with an identical east-looking geometry. The differing appearance of the second image has intrigued Magellan scientists, because of the possibility that the bright patches observed in cycle 2 may have been caused by rearrangement of loose soil material between March and November 1991. However, by duplicating the cycle 1 viewing geometry in cycle 3, the surface change theory has been tentatively ruled out. Instead, the radar brightness variations are attributed to reflections from an undulating surface, such as sand ripples or small dunes, that have an asymmetry in the east-west direction. The deposits are apparently associated with a 78 kilometers (48 miles) diameter impact crater, Stowe, which lies about 500 kilometers (310 miles) to the northeast. The fine-grained material created during the impact event may have settled out to form the unusual surface deposits observed here. Scientists are now trying to determine if the proposed ripple structures formed at the time of the impact, or are the result of ongoing wind action at the surface. Data quality during portions of cycle 3 was adversely affected by a faulty transmitter aboard the spacecraft, leading to the missing strips in the bottom image. PUBLIC INFORMATION OFFICE Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-40697 MGN-106 August 11, 1992 This computer-generated perspective view of Latona Corona and Dali Chasma on Venus shows Magellan radar data superimposed on topography. The view is from the northeast and vertical exaggeration is 10 times. Exaggeration of relief is a common tool scientists use to detect relationships between structure (i.e., faults and fractures) and topography. Latona Corona, a circular feature approximately 1000 kilometers or (620 miles) in diameter whose eastern half is shown at the left of the image, has a relatively smooth, radar-bright raised rim. Bright lines or fractures within the corona appear to radiate away from its center toward the rim. The rest of the bright fractures in this area are associated with the relatively deep (approximately 3 kilometers or 1.9 miles) troughs of Dali Chasma. The Dali and Diana Chasma system consist of deep troughs that extend for 7,400 kilometers (4,588 miles) and are very distinct features on Venus. These chasma connect the Ovda and Thetis highlands with the large volcanoes at Atla Regio and thus are considered to be the "Scorpion Tail" of Aphrodite Terra. The broad, curving scarp resembles some of Earth's subduction zones where crustal plates are pushed over each other. The radar bright surface at the highest elevation along the scarp is similar to surfaces in other elevated regions where some metallic mineral such as pyrite (fool's gold) may occur on the surface. PUBLIC INFORMATION OFFICE Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-40698 MGN-107 August 11, 1992 This Magellan mosaic centered at 12.5 degrees south latitude, 261 degrees east longitude, shows an unnamed volcano that straddles a narrow, angular fracture system extending southeastward from Phoebe Regio, a highland tessera, or tile-appearing, region. The image, which shows an area approximately 587 kilometers (364 miles) on a side, is a synthetic aperture radar (SAR) backscatter image combined with a color radio-thermal emission (emissivity) image. The red corresponds to a high emissivity, blue to a low emissivity. The emissivity, which is a measure of the electrical properties of surface materials, is an important clue for understanding surface composition. While many Magellan images display just the radar backscatter in order to obtain information about the shape and roughness of features, there are other important data sets including the surface topography obtained from the Magellan altimeter and the emissivity. Information to derive emissivity is recorded when Magellan's radar antenna ceases to send signals to the surface and instead listens to the radio waves naturally emitted from the surface. This volcano exhibits what scientists have noticed to be a widespread phenomenon on Venus -- the occurrence of lower emissivities at higher altitudes. The summit of the volcano, which is about 2 kilometers (1.2 miles) in height, displays the lowest emissivity, while the emissivity becomes progressively greater toward lower elevations. The presence of minerals such as pyrrohtite or pyrite may explain the low emissivities in some cases because of their electrical properties and their stability at the temperatures and pressures found at high altitudes on Venus. The image was produced at the JPL Multimission Image Processing Laboratory. MAGELLAN PROJECT OFFICE P-40699 8/14/92 Maat Mons is displayed in this computer generated three-dimensional perspective view of the surface of Venus. This image was created on Caltech's Intel Touchstone Delta Supercomputer. The viewpoint is located near the face of Maat Mons. The view is to the east with the volcano Maat Mons appearing at the center of the image on the horizon. Maat Mons is located at approximately 0.9 degrees north latitude, 194.5 degrees east longitude with a peak that ascends to 8 kilometers (5 miles) above the mean surface. Maat Mons is named for an Egyptian Goddess of truth and justice. Magellan synthetic aperture radar data is combined with radar altimetry to develop a three-dimensional map of the surface. The vertical scale in this perspective has been exaggerated 10 times. Rays cast in a computer intersect the surface to create a three-dimensional perspective view. A digital elevation map developed by the U.S. Geological Survey is used to enhance small-scale structure. The image was produced by the Solar System Visualization project, the Magellan Science Team at the JPL Multimission Image Processing Laboratory and the Digital Image Animation Laboratory, and is a single frame from a video being created on the Delta Supercomputer. This work is part of NASA's "Grand Challenge" research effort in the planetary science applications of high performance computers. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-40700 8/14/92 Maat Mons is displayed in this computer generated three-dimensional perspective view of the surface of Venus. This image was created on Caltech's Intel Touchstone Delta Supercomputer. The viewpoint is located 634 kilometers (393 miles) north of Maat Mons at an elevation of 3 kilometers (2 miles) above the terrain. Lava flows extend for hundreds of kilometers across the fractured plains shown in the foreground, to the base of Maat Mons. The view is to the south with the volcano Maat Mons appearing at the center of the image on the horizon and rising to almost 5 kilometers (3 miles) above the surrounding terrain. Maat Mons is located at approximately 0.9 degrees north latitude, 194.5 degrees east longitude with a peak that ascends to 8 kilometers (5 miles) above the mean surface. Maat Mons is named for an Egyptian Goddess of truth and justice. Magellan synthetic aperture radar data is combined with radar altimetry to develop a three-dimensional map of the surface. The vertical scale in this perspective has been exaggerated 10 times. Rays cast in a computer intersect the surface to create a three-dimensional perspective view. A digital elevation map developed by the U.S. Geological Survey is used to enhance small-scale structure. The image was produced by the Solar System Visualization project, the Magellan Science Team at the JPL Multimission Image Processing Laboratory and the Digital Image Animation Laboratory, and is a single frame from a video being created on the Delta Supercomputer. This work is part of NASA's "Grand Challenge" research effort in the planetary science applications of high performance computers. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-40701 8/14/92 Sapas Mons is displayed in this computer generated three-dimensional perspective view of the surface of Venus. This image was created on Caltech's Intel Touchstone Delta Supercomputer. The viewpoint is located 243 kilometers (151 miles) south of Sapas Mons. Lava flows extend for hundreds of kilometers from the large volcano into the smooth plains. The view is to the north with the volcano Sapas Mons appearing at the center of the image at approximately 0.9 degrees north latitude, 188 degrees east longitude with two peaks that ascend to 3 kilometers (1.8 miles) above the mean surface. Sapas Mons is named after an ancient Phoenician Goddess. Magellan synthetic aperture radar data is combined with radar altimetry to develop a three-dimensional map of the surface. The vertical scale in this perspective has been exaggerated 10 times. Rays cast in a computer intersect the surface to create a three-dimensional perspective view. A digital elevation map developed by the U.S. Geological Survey is used to enhance small-scale structure. The image was produced by the Solar System Visualization project, the Magellan Science Team at the JPL Multimission Image Processing Laboratory and the Digital Image Animation Laboratory, and is a single frame from a video being created on the Delta Supercomputer. This work is part of NASA's "Grand Challenge" research effort in the planetary science applications of high performance computers. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-40752 1/12/93 This perspective view of the synthetic aperture radar (SAR) image of part of Bereghinya Planitia is false-colored to show the thermal emissivity (the amount of energy radiated by the surface at a given temperature, relative to the maximum amount for a perfect radiator). Emissivity varies somewhat for different rock types, and is more strongly affected by the small-scale surface texture: rougher, more porous surfaces tend to have higher emissivities. In this image purple represents an emissivity of 0.81, and red an emissivity of 0.88. The base image is a compressed once mosaicked image data record (C1-MIDR) which is a standard Magellan data product with a resolution of 0.255 kilometer/pixel, processed to enhance small features. The Magellan altimeter dataset was used to determine the shape, and thus the appearance in perspective, of the surface. Shading based on the altimetric shape (with illumination from the right in this view) was also added to the image in order to emphasize large-scale topographic features. The view is from approximately 33.88 degrees north latitude, 18.80 degrees east longitude, looking due west along a chain of arachnoids, "spider-like" features that have raised rims surrounding a central depression and are characterized by both concentric and radiating patterns of bright fractures. The bright feature in the foreground is a lava flow. The image has been vertically exaggerated by a factor of 20. Image processing was performed for the Magellan project by the U.S. Geological Survey, Flagstaff, Arizona. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-40753 1/12/93 This synthetic aperture radar (SAR) image of part of Bereghinya Planitia is false-colored to show altimetry data. Purple represents a radius of 6050.35 kilometers from the center of Venus, and red a radius of 6052.65 kilometers (the mean radius of the planet is 6051.8 kilometers). Geologically, this area consists of lowland lava plains, criss-crossed by chains of arachnoids. These "spider-like" features have raised rims surrounding a central depression and are characterized by both concentric and radiating patterns of bright fractures. A regional upward slope to the north is apparent. The base image is a compressed once mosaicked image data record (C1-MIDR) which is a standard Magellan data product with a resolution of 0.225 kilometer/pixel and is in a sinusoidal equal-area map projection. This image, centered at 45 degrees north latitude, 11 degrees east longitude, is 1613 kilometers from top to bottom and 1843 kilometers from side to side. The base image has been digitally processed to enhance small features. The intensity (brightness) information in the SAR image has been preserved, but color has been added to indicate the variation of elevations mapped by the Magellan altimeter. Image processing was performed for the Magellan project by the U.S. Geological Survey, Flagstaff, Arizona. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-40754 1/12/93 This synthetic aperture radar (SAR) image of part of Aphrodite Terra is false-colored to show the thermal emissivity (the amount of energy radiated by the surface at a given temperature, relative to the maximum amount for a perfect radiator). Purple represents an emissivity of 0.50, and red an emissivity of 0.89. Emissivity varies somewhat for different rock types, and is strongly affected by small scale surface texture: rougher, more porous surfaces tend to have higher emissivities. These relatively subtle effects are swamped by an abrupt decrease in emissivity at high elevations (greater than about 6054 kilometers from the center of the planet) almost everywhere on Venus. This decrease is believed to be due to the reaction of rocks in high, relatively cool locations with the atmosphere, forming a highly conductive mineral phase. The base image is a compressed once mosaicked image data record (C1-MIDR) which is a standard Magellan data product with a resolution of 0.225 kilometer/pixel and is in a sinusoidal equal-area projection. This image, centered at 15 degrees south latitude, 129 degrees east longitude, is 1613 kilometers from top to bottom and 1843 kilometers from side to side. The base image has been digitally processed to enhance small features. The southern edge of Aphrodite Terra, a continent-sized region of highlands centered on the Venusian equator, runs roughly horizontally across the center of the image. This highland is made up principally of complex ridged terrain (formerly called tesserae, because of their resemblance to an inlaid parquet floor) that is believed to have been formed by extensive crustal deformation. Image processing was performed for the Magellan Project by the U.S. Geological Survey, Flagstaff, Arizona. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-40755 1/12/93 This synthetic aperture radar (SAR) image of part of Aphrodite Terra is false-colored to show variations in meter scale roughness of the surface. This dataset is sensitive to slopes that extend over distances larger than the radar wavelength (tens of centimeters) but smaller than the area sampled by the instrument (tens of kilometers). In this image, purple represents a typical or root-mean-square (RMS) slope of 3.0 degrees, and red a RMS slope of 19.2 degrees. The greater roughness of the highlands compared to the lowland plains is readily apparent. The base image is a compressed once mosaicked image data record (C1-MIDR) which is a standard Magellan data product with a resolution of 0.225 kilometer/pixel and is in a sinusoidal equal-area projection. This image, centered at 15 degrees south latitude, 129 degrees east longitude, is 1613 kilometers from top to bottom and 1843 kilometers from side to side. The base image has been digitally processed to enhance small features. The southern edge of Aphrodite Terra, a continent-sized highland centered on the Venusian equator, runs roughly horizontally across the center of the image. This highland is made up principally of complex ridged terrain (formerly called tesserae, because of their resemblance to an inlaid parquet floor) and is believed to have been formed by extensive crustal deformation. To the south are lowland plains that are made up of overlapping lava flows. Image processing was performed for the Magellan Project by the U.S. Geological Survey, Flagstaff, Arizona. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-40756 1/12/93 This synthetic aperture radar (SAR) image of part of Aphrodite Terra is false-colored to show variations in elevation. Purple represents a radius of 6051.7 kilometers from the center of Venus and red a radius of 6055.7 kilometers (the mean radius of the planet is 6051.8 kilometers). This image clearly shows the difference in elevation between the lowland plains in the south and the highlands to the north. A rift is located along the boundary between these two terrains. The base image is a compressed once mosaicked image data record (C1-MIDR) which is a standard Magellan data product with a resolution of 0.225 kilometer/pixel and is in a sinusoidal equal-area projection. This image, centered at 15 degrees south latitude, 129 degrees east longitude, is 1613 kilometers from top to bottom and 1843 kilometers from side to side. The base image has been digitally processed to enhance small features. The southern edge of Aphrodite Terra, a continent-sized highland centered on the Venusian equator, runs roughly horizontally across the center of the image. This highland is made up principally of complex ridged terrain (formerly called tesserae, because of their resemblance to an inlaid parquet floor) and is believed to have been formed by extensive crustal deformation. The lowland plains are made up of overlapping lava flows. Image processing was performed for the Magellan Project by the U.S. Geological Survey, Flagstaff, Arizona. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-40757 1/12/93 This synthetic aperture radar (SAR) image of part of Maxwell Montes and Fortuna Tesserae is false-colored to show the thermal emissivity (the amount of energy radiated by the surface at a given temperature, relative to the maximum amount for a perfect radiator). Purple represents the lowest values (an emissivity of 0.40) and red the highest values (an emissivity of 0.90). Emissivity varies somewhat for different rock types, and is strongly affected by small scale surface texture: rougher, more porous surfaces tend to have higher emissivities. These relatively subtle effects are swamped by the abrupt decrease in emissivity at high elevations (greater than about 6054 kilometers from the center of the planet) almost everywhere on Venus. This decrease is believed to be due to the reaction of rocks in high, relatively cool locations with the atmosphere, forming a highly conductive mineral phase. The base image is a full resolution basic image data record (F-MIDR) which is a standard Magellan data product with a resolution of 0.075 kilometer/pixel and is in a sinusoidal equal-area projection. This image, centered at 66 degrees north latitude, 12 degrees east longitude, is 538 kilometers from top to bottom and 614 kilometers from side to side. The base image has been digitally processed to enhance small features. Maxwell Montes, the highest mountain range on Venus, occupies approximately the left most one-third of the image, with its summit just outside the area shown. The remainder of the image covers part of Fortuna Tesserae, a region of complex ridged terrain that is believed to have been formed by extensive deformation of the Venusian crust. In the left center of the image is the 105-kilometer diameter crater Cleopatra. Prior to the Magellan mission, it was not clear whether Cleopatra was an impact crater or a volcano; a thin channel can be seen leading from the inner crater to a lava-flooded area to the east, but this is now believed to be the result of impact-triggered melting rather than volcanism. The impact nature of Cleopatra is clearly demonstrated by its ejecta, which partially blanket the ridges in the nearby terrain. Image processing was performed for the Magellan Project by the U.S. Geological Survey, Flagstaff, Arizona. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-40844 9/8/92 This Magellan mosaic centered at 12.5 degrees south latitude, 261 degrees east longitude, shows an unnamed volcano that straddles a narrow, angular fracture system extending southeastward from the Phoebe Regio highlands. The image, which shows an area approximately 587 kilometers (364 miles) on a side, is a synthetic aperture radar (SAR) backscatter image. While Magellan SAR images obtain information about the shape and roughness of features, there are other important data sets including the surface topography obtained from the Magellan altimeter and the emissivity. This volcano exhibits what scientists have noticed to be a widespread phenomenon on Venus -- the occurrence of lower emissivities at higher altitudes. The summit of the volcano, which is about 2 kilometers (1.2 miles) in height, displays the lowest emissivity, while the emissivity becomes progressively greater toward lower elevations. The presence of minerals such as pyrrohtite or pyrite may explain the low emissivities in some cases because of their electrical properties and their stability at the temperatures and pressures found at high altitudes on Venus. The image was produced at the JPL Multimission Image Processing Laboratory. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 PUBLIC INFORMATION OFFICE Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION Magellan P-40991 MGN-108 September 21, 1992 This Magellan image, centered at 41.3 degrees south latitude, 328.3 degrees east longitude on Venus, was obtained in early September 1992, near the end of the third mapping cycle. Dimensions of the area imaged are approximately 44 kilometers by 36 kilometers (27 miles by 22 miles). The radar-bright lineaments appear to be scarps associated with surface faulting and extension. The area pictured lies approximately 200 kilometers (124 miles) southeast of the volcano Hathor Mons, which rises about 2 kilometers (1.2 miles) above the surrounding plain. Hathor and two other large volcanoes, Ushas and Innini, were imaged by Magellan for the first time this September. This region was the largest single remaining gap in the Magellan global radar image map. The area of Venus covered by Magellan is now approximately 99% of the planet's surface or 455 million square kilometers (172 million square miles). That is approximately three times the land area of all of the Earth's continents combined. MAGELLAN PROJECT OFFICE P-41005 10/20/92 This poster explains how Magellan radar data is processed into images. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 PUBLIC INFORMATION OFFICE Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION Magellan P-41056 MGN-109 October 16, 1992 Crater Isabella, with a diameter of 175 kilometers (108 miles), seen in this Magellan radar image, is the second largest impact crater on Venus. The feature is named in honor of the 15th century queen of Spain, Isabella of Castile. Located at 30 degrees south latitude, 204 degrees east longitude, the crater has two extensive flow-like structures extending to the south and to the southeast. The end of the southern flow partially surrounds a pre-existing 40 kilometer (25 mile) circular volcanic shield. The southeastern flow shows a complex pattern of channels and flow lobes, and is overlain at its southeastern tip by deposits from a later 20 kilometer (12 mile) diameter impact crater, Cohn (for Carola Cohn, Australian artist, 1892-1964). The extensive flows, unique to Venusian impact craters, are a continuing subject of study for a number of planetary scientists. It is thought that the flows may consist of "impact melt," rock melted by the intense heat released in the impact explosion. An alternate hypothesis invokes "debris flows," which may consist of clouds of hot gases and both melted and solid rock fragments that race across the landscape during the impact event. That type of emplacement process is similar to that which occurs in violent volcanic eruptions on Earth, such as the 1991 Mount Pinatubo eruption in the Philippines. MAGELLAN PROJECT OFFICE P-41147 10/20/92 This global view of the surface of Venus is centered at 180 degrees east longitude. Magellan synthetic aperture radar mosaics from the first cycle of Magellan mapping are mapped onto a computer-simulated globe to create this image. Data gaps are filled with Pioneer-Venus Orbiter data, or a constant mid-range value. The image was produced at the JPL Multimission Image Processing Laboratory and is a single frame from a video released at the October 29, 1991, JPL news conference. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-41293 1/15/93 This Magellan image of volcanic features and an impact crater with a dark streak is located on the northern flank of Western Eistla Regio, centered near 26 degrees north latitude, 354 degrees east longitude, and covers an area 530 kilometers (329 miles) by 220 kilometers (136 miles). Radar- bright lava flows originating from the volcanoes Sif Mons and Gula Mons are located at the left and right hand sides of the image respectively. The 500 kilometer (310 mile) radar-dark streak cuts across a volcanic feature and terminates at a 10 kilometer (6 mile) diameter impact crater at the right side of the image. The streak is an area where the surface is smooth and is thought to have formed by shock waves transmitted through the atmosphere during the impact process. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-41294 1/15/93 This image of the central part of Beta Regio is centered at 28 degrees north latitude, 283 degrees east longitude and covers a region 1170 kilometers (725 miles) by 630 kilometers (391 miles). Lying along a north- south trend is the 1050 kilometers (651 miles) long rift valley Devana Chasma. The rift is similar to areas on the earth such as the east African Rift where the crust is being stretched and faulted. Located at the bottom left of the image is the 5 kilometer (3 mile) high volcano Theia Mons. Lava flows from this volcano contribute to infilling of the rift. Faulting along the western edge of Devana cut the volcano and its deposits indicating that the emplacement of lava and faulting have been ongoing processes. The rift is widest, 240 kilometers (149 miles), in the vicinity of Theia Mons and narrows to a width of 80 kilometers (50 miles) where it intersects a region of tessera to the north. Rhea Mons, located on the western side of the rift, is located near the top center of the image and is distinguished by a radar-dark oval area at its summit. The 37 kilometers (23 miles) diameter impact crater Somerville is located to the south of Rhea within Devana Chasma. The rim of this crater has been faulted due to extension and separated by a distance of approximately 10 kilometers (6 miles). Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-41295 1/15/93 This image, centered at 10 degrees south latitude, 78 degrees east longitude covers a region 2500 kilometers (1550 miles) by 500 kilometers (310 miles) along the southern flank of Aphrodite Terra. The highland of Aphrodite is a large area of complex ridged terrain also known as tessera. Its complex structure shows evidence of both compressional and extensional deformation. Located along the southern edge of this upland is a zone of fracturing and faulting 1000 kilometers (620 miles) long and 100 kilometers (62 miles) wide that corresponds to Ix Chel Chasma. A radar-dark oval depression 150 kilometers (93 miles) long and 80 kilometers (50 miles) wide corresponds to a large volcanic caldera located at the right hand part of the image. A radar-bright area to the north and west of the caldera corresponds to a site where material on the surface is electrically conductive and is thought to represent the presence of metallic minerals in the rock. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-41429 12/21/92 The set of Magellan radar images shown here demonstrates the use of stereo data to produce high resolution topography information. The first two images of the 24 kilometers (15 miles) diameter impact crater Riley, located at 14.05 degrees north latitude, 72.3 degrees east longitude, are from Magellan's first and third mapping cycles, respectively. The look angles for the two cycles are slightly different, allowing the images to be viewed in stereo. The third image is an orthorectified (radar distortions removed) view of the crater that is combined with topography data taken from a digital elevation model (DEM). The DEM is created using an algorithm that determines elevations from the displacement of identical features in both images. The abrupt boundary in elevations along the left part of the crater is due to missing Cycle 3 data. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-41461 12/22/92 This Magellan image mosaic shows the largest (280 kilometers in diameter [174 miles]) impact crater known to exist on Venus. The crater is located to the north of Aphrodite Terra and to the east of Eistla Regio at latitude 12.5 degrees north latitude and 57.2 degrees east longitude. The International Astronomical Union-Commission on Planetary Nomenclature has approved Mead, after Margaret Mead--the American Anthropologist (1901- 1978), as the official name for this crater. Mead is a multi-ring crater with its innermost, concentric scarp interpreted to be the rim of the original crater cavity. No inner peak- ring of mountain massifs is observed on Mead. The presence of hummocky, radar-bright ejecta that crosses the radar-dark floor terrace and adjacent outer rim scarp suggests that the floor terrace is a giant rotated block that is concentric to, but lies outside of, the original crater cavity. The flat, somewhat brighter inner floor of Mead is interpreted to result from considerable infilling of the original crater cavity by impact melt and/or by volcanic lavas. To the southeast of the crater rim, emplacement of hummocky ejecta appears to have been impeded by preexisting ridges, thus suggesting a very low ground-hugging mode of deposition for this material. Radar illumination on this Magellan image is from the left to the right. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 MAGELLAN PROJECT OFFICE P-41592 5/26/93 This Magellan radar image of Ovda Regio is a compilation of data collected during all three 8 month imaging cycles. Areas where no images were obtained are filled with topography data. The scene is centered at 0 degrees north, 80 degrees east longitude and covers an area 6,300 kilometers by 6,300 kilometers (3,900 miles by 3,900 miles). Ovda rises to an elevation of over 3 kilometers (1.9 miles) above the surrounding radar-dark (smooth) plains and is made up of a complexly deformed terrain known as tesserae. A band of east-west trending ridges located along the north central part of Ovda, near the center of the image, are interpreted to have formed by NW-SE oriented compression. Along the southern edge of the highland is a 200 kilometer (124 mile) wide zone of faulting and fracturing formed by extension. Near the northwest edge of Ovda (12.5 degrees north latitude, 57.2 degrees east longitude) is the 280 kilometer (174 mile) diameter impact crater Mead. A second, 31 kilometer (19 mile) diameter crater named Adivar, has a radar-dark parabola shaped deposit and is located to the northwest of the belt of ridges that form the northern edge of the highland. The radar-bright material at the eastern part of Ovda (center left-hand part of the image) corresponds to the highest part of this region. The extreme brightness of this area is due both to a high degree of roughness on the scale of the radar wavelength and the presence of a metallic mineral in the surface rocks. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-41843 4/2/93 The Magellan spacecraft has completed three eight-month global radar mapping cycles at Venus. During most of the second and third cycles, Magellan's radar was pointed at an angle to the surface that was slightly different than the angle used during the first cycle. Among the benefits of these new perspectives of the surface is the opportunity to measure the heights, depths and shapes of features with remarkable accuracy. In this example, a steep-sided, partially collapsed volcanic dome is viewed from opposite sides - from the left in Cycle 1 (left) and from the right in Cycle 2 (right). The dome, approximately 40 kilometers (25 miles) in diameter, lies at 16 degrees south latitude, 211.5 degrees east longitude, southeast of Atla Regio. The Cycle 1 image used an incidence angle of 40 degrees from vertical, which leads to a distortion of the image known as foreshortening. The top of the dome appears "pulled over" to the left, so that the apparent distance between the upper scarp and the westernmost pit at the base of the dome is 118 picture elements, or pixels. At 75 meters (246 feet) per pixel, this apparent distance is 8.85 kilometers (5.5 miles). In the Cycle 2 image, with an incidence angle of 25 degrees, the foreshortening is more pronounced and in the opposite direction to that in the Cycle 1 image. The apparent distance between the scarp and the pit is 243 pixels or 18.22 kilometers (11.3 miles). There is a simple mathematical equation that relates these apparent distortions, the incidence angles and the height of the feature. Solving this equation, the height of the dome is found to be 2.6 kilometers (1.6 miles), among the tallest of this class of volcanoes. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 PUBLIC INFORMATION OFFICE Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION Magellan P-41844 MGN-110 March 10, 1993 During the third global cycle of Magellan's radar mapping mission, images were obtained at viewing angles that were slightly different than those used in the first two cycles. This strategy was designed to produce stereo image pairs, which take advantage of distortions induced by the different views to provide details of the surface topography. This is a stereo image pair of crater Geopert-Meyer, named for the 20th century Polish physicist and Nobel laureate (60 degrees north latitude, 26.5 degrees east longitude). The crater, 35 kilometers (22 miles) in diameter, lies above an escarpment at the edge of a ridge belt in southern Ishtar Terra. West of the crater the scarp has more than 1 kilometer (0.6 mile) of relief. Perception of relief may be obtained with stereo glasses or a stereoscope. Some individuals may be able to fuse the images without the aid of those devices. The radar illumination for both images is from the west, or left side of the scene. Incidence angles are: Cycle 1 (left) 28 degrees, Cycle 3 (right) 15 degrees from vertical. Analysis of stereo image pairs allows planetary scientists to resolve details of topographic relationships on Venusian craters, volcanoes, mountain belts, and fault zones. The spatial resolution of this topographic information is approximately ten times better than that obtained by Magellan's altimetry experiment. MAGELLAN PROJECT OFFICE P-41850 4/2/93 The Magellan spacecraft has completed three eight-month global radar mapping cycles at Venus. During most of the second and third cycles, Magellan's radar was pointed at an angle to the surface that was slightly different than the angle used during the first cycle. Among the benefits of these new perspectives of the surface is the opportunity to measure the heights, depths and shapes of features with remarkable accuracy. In this example, a type of volcanic pit known as a caldera is viewed from the west side at two different angles - 42 degrees from the vertical in Cycle 1 (left) and 23 degrees from the vertical in Cycle 3 (right). The two images may be fused to form a three dimensional image by using a device such as a stereoscope that directs each image exclusively to each eye. The caldera, approximately 50 kilometers (31 miles) in diameter, lies at 9.5 degrees south latitude, 69 degrees east longitude, in the Ovda region of the Aphrodite highlands. The Cycle 1 image used an incidence angle of 42.5 degrees from vertical, which leads to a distortion of the image known as elongation. The western wall of the caldera appears "stretched out", so that the apparent distance between the fractures on the west rim and the floor of the caldera is 376 picture elements, or pixels. At 75 meters (246 feet) per pixel, this apparent distance is 28.2 kilometers (17.5 miles). In the Cycle 3 image, with an incidence angle of 22.7 degrees, the elongation is more pronounced than in the Cycle 1 image. The apparent distance between the fractures and the floor is 399 pixels or 29.9 kilometers (18.5 miles). There is a simple mathematical equation that relates these apparent distortions, the incidence angles and the depth of the feature. Solving this equation, the depth of the caldera is found to be 1.3 kilometers (0.8 miles). Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 PUBLIC INFORMATION OFFICE Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION Magellan P-41937 MGN-111 March 10, 1993 These maps of Venus show how well various regions of the surface radiate heat compared to a perfect radiator. They display in color a quantity called emissivity, observed using a Magellan Synthetic Aperture Radar (SAR) receiver during its 24 months of systematic mapping in Venus orbit. Color is used to code the emission efficiency (see color bar). Red corresponds to the highest, blue to the lowest values of emissivity. The upper image shows the portion of the planet between 69 degrees north and 69 degrees south latitude in Mercator projection; beneath it are the two polar regions covering latitudes above 44 degrees in stereographic projection. The horizontal resolution varies with latitude, being determined solely by the "footprint" of Magellan's high-gain SAR antenna beam. Near the equator the surface resolution is about 20 kilometers (12.4 miles) but at high latitudes it degrades to as much as 100 kilometers (62 miles). Emissivity of the surface is a measure of how well the surface radiates heat. Higher regions, such as the Maxwell Montes (at top left center) and Aphrodite Terra (along the equator at right center), usually show lower values of emissivity than are typical of lower-lying areas. On a cooler planet, such as Earth or Mars, water or ice might explain the puzzling observations but at the surface temperature of Venus -- 470 degrees C (878 F) -- neither can be present. Some theories call for the presence of an electrically- conducting mineral such as pyrite (the minerals have an electrical field when illuminated by radar); others suggest a material as yet unidentified that has an extremely low electrical loss. The data shown here were compiled and analyzed at the Center for Space Research, Massachusetts Institute of Technology. PUBLIC INFORMATION OFFICE Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION Magellan P-41938 MGN-112 March 10, 1993 This map of the topography of Venus was obtained by the Magellan radar altimeter during its 24 months of systematic mapping. Color is used to code elevation (see color bar), and simulated shading to emphasize relief. Red corresponds to the highest, blue to the lowest elevations. The upper image shows the portion of the planet between 69 degrees north and 69 degrees south latitude in Mercator projection; beneath it are the two polar regions covering latitudes above 44 degrees in stereographic projection. Height accuracy is better than 50 meters; horizontal ("footprint") resolution of the surface depends on spacecraft altitude, with a resolution of about 10 kilometers (6 miles) near the equator and as much as 25 kilometers (15.5 miles) at higher latitudes. The Magellan altimeter acquired topography data over 98 percent of the planet's surface. Gray areas show the coarser results from the Pioneer Venus (1978) and Venera 15/16 (1983) radar altimeters, and indicate where data were not obtained by Magellan. The elevated region in the north is Ishtar Terra, dominated by Maxwell Montes (the planet's highest mountains) which rise 11 kilometers (36,000 feet) above the planetary mean elevation. Southwest of Ishtar are the highlands of Beta Regio and Phoebe Regio, which are bisected by a major north-south trending rift zone. The scorpion-shaped feature extending along the equator between 70 and 210 degrees longitude is Aphrodite Terra, a continent-like highland that contains several spectacular volcanoes at its eastern limit: Maat, Ozza and Sapas Montes. The altimetric data shown here were compiled and analyzed at the Center for Space Research, Massachusetts Institute of Technology. MAGELLAN PROJECT OFFICE P-41938AC 4/2/93 This map of the topography of Venus was obtained by the Magellan radar altimeter during its 24 months of systematic mapping. Color is used to code elevation (see color bar), and simulated shading to emphasize relief. Red corresponds to the highest, blue to the lowest elevations. The upper image shows the portion of the planet between 69 degrees north and 69 degrees south latitude in Mercator projection; beneath it are the two polar regions covering latitudes above 44 degrees in stereographic projection. Height accuracy is better than 50 meters; horizontal ("footprint") resolution of the surface depends on spacecraft altitude, with a resolution of about 10 kilometers (6 miles) near the equator and as much as 25 kilometers (15.5 miles) at higher latitudes. The Magellan altimeter acquired topography data over 98 percent of the planet's surface. Gray areas show the coarser results from the Pioneer Venus (1978) and Venera 15/16 (1983) radar altimeters, and indicate where data were not obtained by Magellan. The elevated region in the north is Ishtar Terra, dominated by Maxwell Montes (the planet's highest mountains) which rise 11 kilometers (36,000 feet) above the planetary mean elevation. Southwest of Ishtar are the highlands of Beta Regio and Phoebe Regio, which are bisected by a major north-south trending rift zone. The scorpion-shaped feature extending along the equator between 70 and 210 degrees longitude is Aphrodite Terra, a continent-like highland that contains several spectacular volcanoes at its eastern limit: Maat, Ozza and Sapas Montes. The altimetric data shown here were compiled and analyzed at the Center for Space Research, Massachusetts Institute of Technology. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-41939 3/11/93 These images show the radar reflecting efficiency of the Venus surface when viewed from directly overhead by the Magellan altimeter during its 24 months of systematic mapping. The lightest shades locate areas having the highest values of reflectivity (as high as 70 percent in places), while darker shades indicate areas of low reflection efficiency. The upper image shows the portion of the planet between 69 degrees north and 69 degrees south latitude in Mercator projection; beneath it are the two polar regions covering latitudes above 44 degrees in stereographic projection. Resolution of the surface varies with spacecraft altitude, form about 10 kilometers near the equator to as much as 25 kilometers at high latitudes. Black areas indicate where no data were obtained by Magellan. There is a tendency for elevated regions, e.g. the Maxwell Montes (bright feature at top center) and Aphrodite Terra (along the equator at right), to show higher values of reflectivity than are typical of lower-lying areas. The highest values (greater than 30 percent) are puzzling to understand. On a cooler planet such as Earth or Mars, water or ice might explain the observations, but at the 470-degree-Celsius temperature of the Venus surface, neither can be present. Some theories require the presence of electrically conducting minerals such as pyrite; others suggest a material, as yet unidentified, that has extremely low electrical loss. The data shown here were compiled and analyzed at the Center for Space Research, Massachusetts Institute of Technology. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-41959 4/1/93 This poster explains how Magellan data is processed into gravity measurements. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, Calif. 91109 PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIFORNIA 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-42356AC MGN-113 May 26, 1993 Magellan's fourth eight-month cycle of Venus mapping, which began in September 1992, was dedicated to collecting gravity data. The computer-generated perspective shown here compares gravity and topography over a region 12,700 kilometers by 8,450 kilometers (7,860 miles by 5,240 miles) and extends from longitudes 180 degrees east to 300 degrees east and latitudes 40 degrees north to 40 degrees south. The highlands of Beta Regio and Atla Regio, sites of rifting and large volcanoes, have corresponding high topography and high gravity. These areas are interpreted to be sites where hot mantle material is upwelling, forming "hot spots," similar to areas on Earth such as Hawaii. The two gravity highs at Atla correspond to the volcanoes Maat Mons, the higher of the two peaks, and Ozza Mons respectively. Gravity anomalies at Atla and Beta are the largest on Venus and these may be the sites of relatively young geologic features. In contrast to Earth, it is also seen that there is a near-perfect correlation between gravity and topography with anomalies, both positive (light blue) and negative (dark blue), being correlated with topographic highs and lows. This correspondence is interpreted to indicate that, relative to Earth, the formation of features on Venus is more strongly linked to fluid motions in the mantle. The Magellan mission is managed by the Jet Propulsion Laboratory for NASA's Office of Space Science. MAGELLAN PROJECT OFFICE P-42356BC 5/26/93 Magellan's fourth Cycle of Venus mapping, which began in September of 1992, was dedicated to collecting gravity data. The global gravity map shown here is centered near 330 longitude. Gravity highs are indicated by the reds and yellows and lows by the dark blue. A gravity high corresponding to the highland of Beta Regio, an area of rifting and volcanism, is seen at the left. A second gravity high, centered on the volcanic upland of Western Eistla Regio, is located near the center of the image. Both areas are interpreted to be sites of mantle upwelling forming "hot spots", similar to areas on the Earth such as Hawaii. In the high northern and southern latitudes no a priori constraint, information based on theoretical analysis, is used to determine the gravity field. Since the resolution of the gravity data decreases with increasing spacecraft altitude (Magellan was at an altitude greater than 700 km (430 miles) in the high northern and southern latitudes), the red "waffled" features are regions where the gravity field is very poorly determined. Gravity data obtained after Magellan is placed in a circular orbit will be greatly improved in these polar regions and will give a global view at a constant resolution. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-42359 5/26/93 Magellan's fourth Cycle of Venus mapping, which began in September of 1992, was dedicated to collecting gravity data. This simple schematic shows the method by which Magellan gravity data are acquired. Gravity anomalies are expressed as changes in the planet's gravity field due to the presence of irregularities, such as mountains, valleys, craters, and/or regions of different density materials at or below the surfaced. These irregularities cause the orbiting spacecraft to speed up or slow down. The small changes in speed (less than one millimeter/sec2) or accelerations are gravity data. Earth-based radio signals transmitted to the spacecraft and returned to the Earth can resolve speed measurements to 0.1 mm/sec. The frequency shift in the received radio signals (Doppler effect) make up the raw gravity observation. The signal is sampled every two seconds and over two million data points have been acquired from the Magellan spacecraft. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIFORNIA 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-42383 MGN-114 May 26, 1993 This global view of the surface of Venus is centered at 90 degrees east longitude. Magellan synthetic aperture radar mosaics from the three eight-month cycles of Magellan radar mapping are mapped onto a computer-simulated globe to create this image. Magellan obtained coverage of 98 percent of the surface of Venus. Remaining gaps are filled with data from previous Venus missions -- the Venera 15 and 16 radar and Pioneer-Venus Orbiter altimetry -- and data from Earth-based radar observations from the Arecibo radio telescope. Simulated color is used to enhance small-scale structures. The simulated hues are based on color images obtained by the Venera 13 and 14 landing craft. The bright feature near the center of the image is Ovda Regio, a mountainous region in the western portion of the great Aphrodite equatorial highland. The dark areas scattered across the Venusian plains consist of extremely smooth deposits associated with large meteorite impacts. The image was produced by the Solar System Visualization Project and the Magellan Science team at the Jet Propulsion Laboratory Multimission Image Processing Laboratory. The Magellan mission is managed by JPL for NASA's Office of Space Science. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIFORNIA 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-42384 MGN-115 May 26, 1993 The northern hemisphere is displayed in this global view of the surface of Venus. The north pole is at the center of the image, with 0 degrees, 90 degrees, 180 degrees, 270 degrees east longitudes at the 6, 3, 12, and 9 o'clock positions, respectively, of an imaginary clock face. Magellan synthetic aperture radar mosaics from the three eight-month cycles of Magellan radar mapping are mapped onto a computer-simulated globe to create this image. Magellan obtained coverage of 98 percent of the surface of Venus. Remaining gaps are filled with data from previous missions, (the Soviet Venera 15 and 16 radar and Pioneer-Venus Orbiter altimetry) and data from Earth-based radar observations from the Arecibo radio telescope. Simulated color is used to enhance small-scale structures. The simulated hues are based on color images recorded by the Venera 13 and 14 landing craft. Maxwell Montes, the planet's highest mountain at 11 kilometers (6.6 miles) above the average elevation, is the bright feature in the lower center of the image. Other terrain types visible in this image include tessera, ridge belts, lava flows, impact craters and coronae. The image was produced by the Solar System Visualization Project and the Magellan Science team at the Jet Propulsion Laboratory Multimission Image Processing Laboratory. The Magellan mission is managed by JPL for NASA's Office of Space Science. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIFORNIA 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-42385 MGN-116 May 26, 1993 Magellan radar image and altimetry data are combined in this view of three volcanoes in the southern hemisphere of Venus. The colors represent elevations at the surface, with red and magenta being the highest and blue being the lowest. The area shown is centered at 33 degrees south latitude, 326 degrees east longitude, and is 2,300 kilometers by 1,650 kilometers (1,380 miles by 990 miles) in size. The data were acquired in September 1992 during the third and final phase of Magellan's radar mapping cycles. From north to south, the volcanoes are Ushas, Innini and Hathor Montes. Ushas Mons rises slightly less than 2 kilometers (1.2 miles) above the surrounding plains, and is marked by numerous bright lava flows and a set of north-south trending fractures. Innini, at 2.8 kilometers (1.7 miles), and Hathor, at 2.6 kilometers (1.6 miles), are taller than Ushas but are less distinct in the appearance of their volcanic deposits. The chain of three volcanoes is thought to result from a large zone of hot material upwelling from the Venusian mantle, a phenomenon known on Earth as a "hot spot." The image was produced by the Magellan Science Team at the Jet Propulsion Laboratory Multimission Image Processing Laboratory. The Magellan mission is managed by JPL for NASA's Office of Space Science. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIFORNIA 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-42386 MGN-117 May 26, 1993 Ushas Mons, a 2-kilometer-high (1.25-mile) volcano in the southern hemisphere of Venus is shown in this Magellan radar image. The image is centered at 25 degrees south latitude, 323 degrees east longitude, and shows an area approximately 600 kilometers (360 miles) on a side. The volcano is marked by numerous bright lava flows and a set of north-south trending fractures, many of which appear to have formed after the lavas were erupted onto the surface. In the central summit area, however, younger flows remain unfractured. An impact crater can be seen among the fractures in the upper center of the image. The association of faulting and volcanism is common on this type of volcano on Venus, and is believed to result from a large zone of hot material upwelling from the Venusian mantle, a phenomenon known on Earth as a "hot spot." Simulated color is used to enhance small-scale structures. The simulated hues are based on color images recorded by the Venera 13 and 14 landing craft. The data were acquired during the third eight-month cycle of Magellan's radar mapping, which end in September 1992. Several narrow gaps in the Magellan coverage are filled with low-resolution radar data obtained by the Earth-based Arecibo radio telescope. The image was produced by the Solar System Visualization Project and the Magellan Science Team at the Jet Propulsion Laboratory Multimission Image Processing Laboratory. The Magellan mission is managed by JPL for NASA's Office of Space Science. MAGELLAN PROJECT OFFICE P-42387 5/26/93 Ushas Mons, a 2 kilometer high (1.6 mile) volcano in the southern hemisphere of Venus is shown in this Magellan radar image. The image is centered at 25 degrees south latitude, 323 degrees east longitude, and shows an area approximately 600 kilometers (360 miles) on a side. The volcano is marked by numerous bright lava flows and a set of north-south trending fractures, many of which appear to have formed after the lavas were laid down. In the central summit area, however, younger flows remain unfractured. An impact crater can be seen among the fractures in the upper center of the image. The association of faulting and volcanism is common on this type of volcano on Venus, and is believed to result from a large zone of hot material upwelling from the Venusian mantle, a phenomenon known on Earth as a "hot spot". The data were acquired during the final phase of Magellan's radar mapping cycles, in September, 1992. Several narrow gaps in the Magellan coverage are filled with low resolution radar data obtained by the Earth-based Arecibo radio-telescope. The image was produced by the Magellan Science Team at the JPL Multimission Image Processing Laboratory. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-42388 5/26/93 This global view of the surface of Venus is centered at 180 degrees east longitude. Magellan synthetic aperture radar mosaics from the full two years of Magellan radar mapping are mapped onto a computer-simulated globe to create this image. Magellan obtained coverage of 98% of the surface of Venus. Remaining gaps are filled with data from previous Venus missions: the Venera 15/16 radar and Pioneer-Venus Orbiter altimetry. Simulated color is used to enhance small-scale structure. The simulated hues are based on color images recorded by the Venera 13/14 landing craft. The twisting bright features that cross the globe from the lower left toward the upper right are the highly fractured mountains and canyons of the eastern Aphrodite highland. Just to the right of center is the Atla region, dominated by three large volcanoes: Sapas, Maat and Ozza Montes. The image was produced by the Solar System visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIFORNIA 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-42392 MGN-118 May 26, 1993 This computer-generated perspective view of the highland of Ovda Regio on Venus shows Magellan radar data superimposed on topography. This scene is made up of a compilation of radar images collected during all three of Magellan's eight-month mapping cycles. Simulated color, based on color images obtained by the Venera 14 and 15 landers, is used to enhance small-scale structure. The view is from the northeast looking to the southwest and vertical exaggeration is 22.5 times. Exaggeration of relief is a common tool scientists use to enhance relationships between structure (for example, faults and fractures) and topography. Ovda Regio covers an area 6,300 kilometers by 2,100 kilometers (3,900 miles by 1,300 miles), rises over 3 kilometers (1.9 miles) above the surrounding plains, and is made up of complex ridge terrain, also know as tessera. At the bottom right of this scene, along the northern edge of the highland, are a series east-west trending ridges that are interpreted to have formed by northwest-southeast-oriented compression. In several places the ridges are flooded by radar-dark (smooth) lava flows, indicating that volcanic activity postdates the formation of the ridges. The terrain in the interior of Ovda forms a chaotic pattern indicating multiple directions of deformation. The Magellan mission is managed by the Jet Propulsion Laboratory for NASA's Office of Space Science. PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIFORNIA 91109. TELEPHONE (818) 354-5011 PHOTO CAPTION MAGELLAN P-42393 MGN-119 May 26, 1993 This computer-generated perspective view of the highland of Ovda Regio on Venus shows Magellan radar data superimposed on topography. This scene is made up of a compilation of radar images collected during all three of Magellan's eight-month mapping cycles. Simulated color, based on color images obtained by the Venera 14 and 15 landers, is used to enhance small-scale structure. The view is from west to east and vertical exaggeration is 22.5 times. Exaggeration of relief is a common tool scientists use to enhance relationships between structure (for example, faults and fractures) and topography. Ovda Regio covers an area 6,300 kilometers by 2,100 kilometers (3,900 miles by 1,300 miles), rises over 3 kilometers (1.9 miles) above the surrounding plains, and is made up of complex ridge terrain, also know as tessera. Located in the foreground is a 400 kilometer by 250 kilometer (250 mile by 155 mile) oval depression that contains abundant faults and fractures. This feature is surrounded by radar-dark lava flows and is a site of volcanism and extension. The dark volcanic plains flood surrounding complex ridge terrain indicating that lava emplacement postdates the tesserae. The enhanced radar brightness of the complex ridge terrain in the background is due to both roughness on the scale of the radar wavelength and the presence of a metallic mineral in the surface. The Magellan mission is managed by the Jet Propulsion Laboratory for NASA's Office of Space Science. MAGELLAN PROJECT OFFICE P-42611 7/14/93 Magellan's third global cycle of radar mapping was devoted primarily to obtaining repeat coverage of regions seen in previous cycles, using a different viewing angle. The resulting "stereo" pairs provide details of the surface topography at a resolution comparable to the image resolution (about 120 meters or 400 feet). By directing each image exclusively to each eye with a stereoscopic viewer, the images can be fused to create a three-dimensional scene. When viewed with a standard stereoscope, the perceived height differences are exaggerated 5 to 10 times relative to the horizontal scale of the images. In this image, centered at 11.6 degrees south latitude, 89.7 degrees east longitude, channels that once drained molten lava from the site of an eruption extend like tentacles from a large collapse pit. The pit is as deep as 1 kilometer in places. The highlands of Aphrodite Terra, though dominated by tectonically disrupted terrains, also include fresher- appearing volcanic terrains such as this one. The image is 73 kilometers wide. Three-dimensional views of Venus allow geologists to reconstruct the details of geologic events. The high resolution of these stereo image pairs allows the construction of digital topographic maps (digital elevation models or DEMs) from which precise measurements can be made of the heights, depths, slopes and volumes of geologic structures. Magellan observed over 20 per cent of the surface in this dual-perspective mode, and analysis of the third dimension of Venus is sure to continue for decades. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-42612 7/14/93 Magellan's third global cycle of radar mapping was devoted primarily to obtaining repeat coverage of regions seen in previous cycles, using a different viewing angle. The resulting "stereo" pairs provide details of the surface topography at a resolution comparable to the image resolution (about 120 meters or 400 feet). By directing each image exclusively to each eye with a stereoscopic viewer, the images can be fused to create a three-dimensional scene. When viewed with a standard stereoscope, the perceived height differences are exaggerated 5 to 10 times relative to the horizontal scale of the images. In this image, centered at 58.5 degrees north latitude, 26.5 degrees east longitude, the crater Geopert-Meyer (named for the Polish Nobel laureate physicist), is precariously perched at the edge of a deformed mountain belt in Ishtar Terra. The crater rim appears to have been disrupted by later faulting, and its northwest portion has collapsed into the 1 kilometer-deep trough below. The image is 154 kilometers wide. Three-dimensional views of Venus allow geologists to reconstruct the details of geologic events. The high resolution of these stereo image pairs allows the construction of digital topographic maps (digital elevation models or DEMs) from which precise measurements can be made of the heights, depths, slopes and volumes of geologic structures. Magellan observed over 20 per cent of the surface in this dual-perspective mode, and analysis of the third dimension of Venus is sure to continue for decades. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-42613 7/14/93 Magellan's third global cycle of radar mapping was devoted primarily to obtaining repeat coverage of regions seen in previous cycles, using a different viewing angle. The resulting "stereo" pairs provide details of the surface topography at a resolution comparable to the image resolution (about 120 meters or 400 feet). By directing each image exclusively to each eye with a stereoscopic viewer, the images can be fused to create a three-dimensional scene. When viewed with a standard stereoscope, the perceived height differences are exaggerated 5 to 10 times relative to the horizontal scale of the images. In this image, centered at 9.5 degrees south latitude, 69 east longitude, a 1.3 kilometer-deep volcanic caldera lies in a fractured terrain in the Ovda region of Aphrodite Terra. Such features are believed to form by the collapse of the surface following the withdrawal of magma from an underground storage chamber. The smooth, radar-dark floor suggests that lava may have ponded there at a late stage of the caldera's evolution. The image is 60 kilometers wide. Three-dimensional views of Venus allow geologists to reconstruct the details of geologic events. The high resolution of these stereo image pairs allows the construction of digital topographic maps (digital elevation models or DEMs) from which precise measurements can be made of the heights, depths, slopes and volumes of geologic structures. Magellan observed over 20 per cent of the surface in this dual-perspective mode, and analysis of the third dimension of Venus is sure to continue for decades. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-42614 7/14/93 Magellan's third global cycle of radar mapping was devoted primarily to obtaining repeat coverage of regions seen in previous cycles, using a different viewing angle. The resulting "stereo" pairs provide details of the surface topography at a resolution comparable to the image resolution (about 120 meters or 400 feet). By directing each image exclusively to each eye with a stereoscopic viewer, the images can be fused to create a three-dimensional scene. When viewed with a standard stereoscope, the perceived height differences are exaggerated 5 to 10 times relative to the horizontal scale of the images. In this image, centered at 7 degrees south latitude, 69.6 degrees east longitude, isolated hills and ridges are all that remain from a region of tessera in western Aphrodite that has subsided and been flooded by later volcanic flows. Remnants of tessera are found in virtually all regions of Venus, and may represent an earlier era of widespread tectonic deformation. The image is 77 kilometers wide. Three-dimensional views of Venus allow geologists to reconstruct the details of geologic events. The high resolution of these stereo image pairs allows the construction of digital topographic maps (digital elevation models or DEMs) from which precise measurements can be made of the heights, depths, slopes and volumes of geologic structures. Magellan observed over 20 per cent of the surface in this dual-perspective mode, and analysis of the third dimension of Venus is sure to continue for decades. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-42615 7/14/93 Magellan's third global cycle of radar mapping was devoted primarily to obtaining repeat coverage of regions seen in previous cycles, using a different viewing angle. The resulting "stereo" pairs provide details of the surface topography at a resolution comparable to the image resolution (about 120 meters or 400 feet). By directing each image exclusively to each eye with a stereoscopic viewer, the images can be fused to create a three-dimensional scene. When viewed with a standard stereoscope, the perceived height differences are exaggerated 5 to 10 times relative to the horizontal scale of the images. In this image, centered at 41.8 degrees north latitude, 89.6 east longitude, at the eastern edge of the Tellus upland, large quasi-circular areas of tessera appear to have collapsed and been flooded by volcanic materials. Numerous small volcanic domes (1 to 5 kilometer diameter) have formed on the smooth plain developed in the low-lying areas. The image is 154 kilometers wide. Three-dimensional views of Venus allow geologists to reconstruct the details of geologic events. The high resolution of these stereo image pairs allows the construction of digital topographic maps (digital elevation models or DEMs) from which precise measurements can be made of the heights, depths, slopes and volumes of geologic structures. Magellan observed over 20 per cent of the surface in this dual-perspective mode, and analysis of the third dimension of Venus is sure to continue for decades. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-42616 7/14/93 Magellan's third global cycle of radar mapping was devoted primarily to obtaining repeat coverage of regions seen in previous cycles, using a different viewing angle. The resulting "stereo" pairs provide details of the surface topography at a resolution comparable to the image resolution (about 120 meters or 400 feet). By directing each image exclusively to each eye with a stereoscopic viewer, the images can be fused to create a three-dimensional scene. When viewed with a standard stereoscope, the perceived height differences are exaggerated 5 to 10 times relative to the horizontal scale of the images. This image shows Warren crater located at 11.8 degrees south latitude, 176.5 degrees east longitude. The image is 90 kilometers in width. Warren crater, named for the American colonial woman of letters Mercy Warren, is among the larger impact craters of Venus, with a diameter of 50 kilometers. Much of the floor of the crater consists of a relatively smooth, yet radar- bright material of unknown composition. Most of the tectonic deformation of this area, which is associated with the Dali Chasma trough system to the south, appears to pre-date the impact event. Three-dimensional views of Venus allow geologists to reconstruct the details of geologic events. The high resolution of these stereo image pairs allows the construction of digital topographic maps (digital elevation models or DEMs) from which precise measurements can be made of the heights, depths, slopes and volumes of geologic structures. Magellan observed over 20 per cent of the surface in this dual-perspective mode, and analysis of the third dimension of Venus is sure to continue for decades. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-42617 7/14/93 Magellan's third global cycle of radar mapping was devoted primarily to obtaining repeat coverage of regions seen in previous cycles, using a different viewing angle. The resulting "stereo" pairs provide details of the surface topography at a resolution comparable to the image resolution (about 120 meters or 400 feet). By directing each image exclusively to each eye with a stereoscopic viewer, the images can be fused to create a three-dimensional scene. When viewed with a standard stereoscope, the perceived height differences are exaggerated 5 to 10 times relative to the horizontal scale of the images. A zone of fracturing and extension emanates from the southwest margin of Latona Corona. The valleys developed in this rift zone clearly indicate that the crust has been pulled apart in an east-west direction, opening gashes and down-dropping intervening blocks known as graben. The image is centered at 25.7 degrees south latitude, 166 degrees east longitude, and is 98 kilometers wide. Three-dimensional views of Venus allow geologists to reconstruct the details of geologic events. The high resolution of these stereo image pairs allows the construction of digital topographic maps (digital elevation models or DEMs) from which precise measurements can be made of the heights, depths, slopes and volumes of geologic structures. Magellan observed over 20 per cent of the surface in this dual-perspective mode, and analysis of the third dimension of Venus is sure to continue for decades. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-42618 7/14/93 Magellan's third global cycle of radar mapping was devoted primarily to obtaining repeat coverage of regions seen in previous cycles, using a different viewing angle. The resulting "stereo" pairs provide details of the surface topography at a resolution comparable to the image resolution (about 120 meters or 400 feet). By directing each image exclusively to each eye with a stereoscopic viewer, the images can be fused to create a three-dimensional scene. When viewed with a standard stereoscope, the perceived height differences are exaggerated 5 to 10 times relative to the horizontal scale of the images. The Diana Chasma-Dali Chasma trough system dominates the topography of east-central Aphrodite Terra. Shown here is a portion of Diana Chasma that displays total relief of about 6 kilometers. Controversy exists concerning the origin of these great valleys. One theory involves a process similar to that found at the Earth's subduction zones. The image is centered at 14 degrees south latitude, 155.5 degrees east longitude and is 151 kilometers wide. Three-dimensional views of Venus allow geologists to reconstruct the details of geologic events. The high resolution of these stereo image pairs allows the construction of digital topographic maps (digital elevation models or DEMs) from which precise measurements can be made of the heights, depths, slopes and volumes of geologic structures. Magellan observed over 20 per cent of the surface in this dual-perspective mode, and analysis of the third dimension of Venus is sure to continue for decades. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-42619 7/14/93 Magellan's third global cycle of radar mapping was devoted primarily to obtaining repeat coverage of regions seen in previous cycles, using a different viewing angle. The resulting "stereo" pairs provide details of the surface topography at a resolution comparable to the image resolution (about 120 meters or 400 feet). By directing each image exclusively to each eye with a stereoscopic viewer, the images can be fused to create a three-dimensional scene. When viewed with a standard stereoscope, the perceived height differences are exaggerated 5 to 10 times relative to the horizontal scale of the images. One of Magellan's most intriguing discoveries was the class of volcanoes known as steep-sided domes or "pancakes." Centered at 25.9 degrees south latitude, 80 degrees east longitude, this dome sits near the rim of a corona-like structure in Aino Planitia. At 40 kilometers in diameter and near 2 kilometers in height, this dome is much larger than the terrestrial rhyolite domes that provide Earth's best analog. The image is 90 kilometers wide. Geologists are continuing to analyze data on the steep- sided domes to determine the composition and dynamics of their lavas. Three-dimensional views of Venus allow geologists to reconstruct the details of geologic events. The high resolution of these stereo image pairs allows the construction of digital topographic maps (digital elevation models or DEMs) from which precise measurements can be made of the heights, depths, slopes and volumes of geologic structures. Magellan observed over 20 per cent of the surface in this dual-perspective mode, and analysis of the third dimension of Venus is sure to continue for decades. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109 MAGELLAN PROJECT OFFICE P-42620 7/14/93 Magellan's third global cycle of radar mapping was devoted primarily to obtaining repeat coverage of regions seen in previous cycles, using a different viewing angle. The resulting "stereo" pairs provide details of the surface topography at a resolution comparable to the image resolution (about 120 meters or 400 feet). By directing each image exclusively to each eye with a stereoscopic viewer, the images can be fused to create a three-dimensional scene. When viewed with a standard stereoscope, the perceived height differences are exaggerated 5 to 10 times relative to the horizontal scale of the images. In this image, Latona Corona, centered at 20.6 degrees south latitude, 172.5 degrees east longitude, is bounded on its north rim by Dali Chasma. The southern half of the corona consists of a series of roughly concentric scarp-and-trough features, the innermost of which is shown here. Near the left edge of the image, the trough is over 4 kilometers deep. The image is 135 kilometers wide. Three-dimensional views of Venus allow geologists to reconstruct the details of geologic events. The high resolution of these stereo image pairs allows the construction of digital topographic maps (digital elevation models or DEMs) from which precise measurements can be made of the heights, depths, slopes and volumes of geologic structures. Magellan observed over 20 per cent of the surface in this dual-perspective mode, and analysis of the third dimension of Venus is sure to continue for decades. Jet Propulsion Laboratory California Institute of Technology National Aeronautics and Space Administration Pasadena, California 91109