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.