Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from hogtown.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests) ID ; Sat, 23 Feb 91 01:47:50 -0500 (EST) Message-ID: Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Sat, 23 Feb 91 01:47:44 -0500 (EST) Subject: SPACE Digest V13 #193 SPACE Digest Volume 13 : Issue 193 Today's Topics: Re: Terraforming, sun shield Re: Commercially-funded Space Probes (was Re: Space Profits) Re: Shapes From Shading? (was: Re: Martian Mystery?) Re: Terraforming, sun shield Re: Terraforming, sun shield Re: Terraforming, sun shield Re: Shapes From Shading? (was: Re: Martian Mystery?) Re: Commercially-funded Space Probes (was Re: Space Profits) Re: Shapes From Shading? (was: Re: Martian Mystery?) Re: Terraforming, sun shield Re: Terraforming, sun shield Re: Terraforming, sun shield Administrivia: Submissions to the SPACE Digest/sci.space should be mailed to space+@andrew.cmu.edu. Other mail, esp. [un]subscription requests, should be sent to space-request+@andrew.cmu.edu, or, if urgent, to tm2b+@andrew.cmu.edu ---------------------------------------------------------------------- Date: 22 Feb 91 16:40:32 GMT From: agate!shelby!snorkelwacker.mit.edu!spool.mu.edu!sdd.hp.com!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo!henry@ucbvax.Berkeley.EDU (Henry Spencer) Subject: Re: Terraforming, sun shield In article <5705@optilink.UUCP> cramer@optilink.UUCP (Clayton Cramer) writes: >... Try big dirigibles in the upper atmosphere, carrying algae >to do the CO2 -> O2 conversion. Much more practical. Well, not really, if what you want is a habitable planet. If you think 90 atmospheres of CO2 with clouds made of sulfuric acid droplets is a hostile environment, 90 atmospheres of *oxygen* has it beat in spades. High-pressure oxygen is corrosive almost beyond imagining, especially when hot. The real problem with terraforming Venus, far more significant than the shortage of water or the nearness to the Sun, is the need to get rid of most of the atmosphere somehow. -- "Read the OSI protocol specifications? | Henry Spencer @ U of Toronto Zoology I can't even *lift* them!" | henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 22 Feb 91 01:44:38 GMT From: sdd.hp.com!news.cs.indiana.edu!ux1.cso.uiuc.edu!usenet@ucsd.edu (Doug McDonald) Subject: Re: Commercially-funded Space Probes (was Re: Space Profits) In article <9324@hub.ucsb.edu> 3001crad@ucsbuxa.ucsb.edu (Charles Frank Radley) writes: > > >+ The other part is the question of when space law will catch >+up and establish guidelines for property rights in space. This is indeed a necessary preliminary for the economic development of space. > > Unfortunately you are too late. No, too early. > The United Nations Treaty on >the Activities of States on the Moon and all Celestial Bodies, >already prohibits the private property rites which you address. So it will have to be changed in order to permit development. The situation is like on the ocean floor: if a fixed location can't be owned, it can't be developed. Even for such less well defined things as fishing in the open ocean, territorial rights are very important. Similar things apply to the ocean floor and Antarctica. Doug McDonald ------------------------------ Date: 22 Feb 91 17:56:05 GMT From: sdd.hp.com!zaphod.mps.ohio-state.edu!lavaca.uh.edu!jetson.uh.edu!acsls@ucsd.edu (Eddie A. McCreary) Subject: Re: Shapes From Shading? (was: Re: Martian Mystery?) In article <9102211652.AA08913@gemini.arc.nasa.gov>, greer%utdssa.dnet%utaivc@utspan.span.nasa.gov writes: [stuff deleted] > Also, what about _Mars: The Movie_, _Miranda: The Movie_, and _LA (you > guessed it): The Movie_. Those weren't all produced from stereographic > pairs were they? Maybe someone from JPL can tell us about shading to > shape inference > > _____________ > Dale M. Greer, whose opinions are not to be confused with those of the > Center for Space Sciences, U.T. at Dallas, UTSPAN::UTADNX::UTDSSA::GREER > While the Bill of Rights burns, Congress fiddles. -- anonymous hmmm, I believe all of these were done from stereographic data, but I could be wrong. As for deriving 3-D data from shading information, it's possible within limits. You must know information on angle of incidence of the light, specular qualities of the object, and you have to make guesses about the object shape at times (i.e. convex or concave). Oddly enough, I was going to write a program over the break to do just this for the mars data. I got a program running to do contrast enhancement, histogram modifications, and median and mean filtering, but I never got the chance to do the 3-D section. I have a couple of papers at home I tracked down on shape from shading theory if anyone needs a reference. Drop me a note. -- Eddie McCreary EMcCreary@uh.edu, Internet To thine own self be true... EMcCreary@UHOU, BITNET University of Houston ------------------------------ Date: 22 Feb 91 21:18:17 GMT From: swrinde!cs.utexas.edu!news-server.csri.toronto.edu!utzoo!henry@ucsd.edu (Henry Spencer) Subject: Re: Terraforming, sun shield In article <1991Feb22.192438.26397@athena.mit.edu> tardis@athena.mit.edu (Ronald G Lovejoy) writes: >I'm not sure that that's really much of a problem. CO2 is a heavier gas >than O2 and since Venus and Earth have about the same mass (and Earth has >1 atmosphere of pressure), a lot of that liberated O2 may escape into space. >Additionally, when these microorganisms take in the carbon and some of the >sulfur, a lot of it will percipitate out of the atmosphere... Unfortunately, O2 is not that much lighter; note that Earth has held an atmosphere of oxygen and nitrogen (even lighter) for geological ages. Having 90 times as much of it doesn't increase the loss rate, in percent per year, much. It isn't going to magically go away. If we want results within mere megayears :-), we have to do something more drastic. The microorganisms take in the carbon and sulfur and precipitate it... but when they die, they get oxidized, and it goes right back into the atmosphere. We have to get rid of the oxygen; that is the big problem. >One possibility for solving the water problem may lie with the sulfuric >acid. ... acids should have a hydrogen radical. By seperating out the >hydrogen and combining it with oxygen, one can supply the water needed >for the algae. Unfortunately, there is really not very much sulfuric acid there. We can get a little bit of water out of it, but not very much. Venus lost almost all of its water long ago through photochemical dissociation into hydrogen and oxygen -- hydrogen *does* escape quickly from Earth-sized planets. >Also, there should be some hydrogen locked up in the rocks on the surface. Very little, by current estimates. Most of the water of hydration has been baked out. -- "Read the OSI protocol specifications? | Henry Spencer @ U of Toronto Zoology I can't even *lift* them!" | henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 22 Feb 91 22:08:22 GMT From: swrinde!cs.utexas.edu!news-server.csri.toronto.edu!helios.physics.utoronto.ca!aurora.physics.utoronto.ca!hall@ucsd.edu (Chris Hall) Subject: Re: Terraforming, sun shield In article <1991Feb22.164032.16901@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes: >In article <5705@optilink.UUCP> cramer@optilink.UUCP (Clayton Cramer) writes: >>... Try big dirigibles in the upper atmosphere, carrying algae >>to do the CO2 -> O2 conversion. Much more practical. > >when hot. The real problem with terraforming Venus, far more significant >than the shortage of water or the nearness to the Sun, is the need to get >rid of most of the atmosphere somehow. We need to put it where the Earth put it's atmosphere; in limestone. That's what the critters are good for. Now the trick would be to get carbonate fixing micro-organisms to settle onto the surface without re-releasing the CO2. At the present surface temperatures of Venus, this might be tricky. Maybe this is where a sun shield could come in handy? Hmmmmmmm Chris M. Hall Dept. of Physics, Geophysics Division University of Toronto, Toronto, Ontario, Canada Internet: hall@aurora.physics.utoronto.ca ------------------------------ Date: 22 Feb 91 17:13:46 GMT From: haven!ncifcrf!fcs260c2!toms@louie.udel.edu (Tom Schneider) Subject: Re: Terraforming, sun shield In article <5705@optilink.UUCP> cramer@optilink.UUCP (Clayton Cramer) writes: >In article <28676.27c07594@kuhub.cc.ukans.edu>, 2fmzmumble@kuhub.cc.ukans.edu writes: >> Problem: Terraform Venus. Method: Orbit a large shield in front of the sun >> to cut incident visible sunlight by 50%. Assume: Manufacturing and > >First problem -- it's own gravitation would cause it crush down to a >little sphere in no time. Any object with a mass equivalent to a >200 mile sphere conforms itself into a round shape, rapidly. I'm >afraid your shield won't last. WHOA! How about giving it a little spin on its axis? Just enough to have it stay spread out! Toss in a few cables if there is too much stress... I bet a good engineer could get you a design that worked! >If you put it in orbit around Venus, it will, as they say, orbit >Venus -- so you don't have much of a shield several hours of the day. OK! But who says he has to have only one? How about a whole bunch of them? It wouldn't matter that they block off the stars at night! Design it so that as one leaves the next slides into place. You could even have them at several different orbital heights to avoid traffic problems... >Clayton E. Cramer {uunet,pyramid,pixar,tekbspa}!optilink!cramer >> Kevin J. Rice Tom 'just a bit of imagination will do it' Schneider National Cancer Institute Laboratory of Mathematical Biology Frederick, Maryland 21702-1201 toms@ncifcrf.gov ------------------------------ Date: 22 Feb 91 20:03:21 GMT From: borg!vangogh!leech@mcnc.org (Jonathan Leech) Subject: Re: Shapes From Shading? (was: Re: Martian Mystery?) In article <1991Feb22.182600.13314@elroy.jpl.nasa.gov>, pjs@euclid.jpl.nasa.gov (Peter Scott) writes: |> I didn't work on these movies, but I attended a technical presentation |> about them a couple of years ago. They use a combination of |> altitude data (where available) and photoclinometry (like you said, |> figuring out shape from shading). People really interested in this might want to track down the Ph.D. thesis (Caltech dept of Geology & Planetary Science)) and publications of Randolph Kirk (no, I don't have references). I know he did a lot of work in this area and I think he's working at JPL these days. I could well be wrong but it seems like some duplication of effort was/is going on in the planetary science and image processing communities in this area. -- Jon Leech (leech@cs.unc.edu) __@/ "Enhanced 386... Runs Unit, Zenix, 0s/s & DOS..." - Competitive Computer Components Ad, Computer Shopper 1/89 ------------------------------ Date: 22 Feb 91 18:08:47 GMT From: bonnie.concordia.ca!news-server.csri.toronto.edu!utzoo!henry@uunet.uu.net (Henry Spencer) Subject: Re: Commercially-funded Space Probes (was Re: Space Profits) In article <9324@hub.ucsb.edu> 3001crad@ucsbuxa.ucsb.edu (Charles Frank Radley) writes: > Unfortunately you are too late. The United Nations Treaty on >the Activities of States on the Moon and all Celestial Bodies, >already prohibits the private property rites which you address. This is the "Moon Treaty" which Brian in fact mentioned. Fortunately, it has been ratified by almost nobody, and in particular the US has not ratified it and isn't going to. It's effectively dead. All glory to the late, lamented L5 Society, which singlehandedly killed it, saving space for free men and thereby earning the undying hatred of the US State Department. For those unfamiliar with it, the Moon Treaty was a particularly ghastly example of rampant socialism at work. No property rights. Inspection of your facilities at any time, without regard for privacy or protection of proprietary processes and without any need to show probable cause. Regulation of your operation by an international "regime" which is also your state-run competitor. Some ill-defined, potentially large, fraction of your revenues to be paid (basically) to the Third World. What, you object to taxation without representation? That's tough; the Moon Treaty mandated it. The only reason this horror had any chance of ratification in the beginning was that nobody had really read it or thought about the implications. > I hope you do not plan to defy the United Nations.......these >days that can become very unpleasant. Defying the UN is usually quite harmless, and often highly desirable since the Third World came to dominate a lot of its decision-making. Korea and Kuwait are the rare exceptions, the first because the Soviet Union stomped out of the Security Council in a huff and wasn't around to veto it, and the second because the Cold War didn't last quite long enough for Saddam Hussein to get his dirty work done under cover of a Soviet veto. -- "Read the OSI protocol specifications? | Henry Spencer @ U of Toronto Zoology I can't even *lift* them!" | henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 22 Feb 91 18:26:00 GMT From: swrinde!elroy.jpl.nasa.gov!euclid.jpl.nasa.gov!pjs@ucsd.edu (Peter Scott) Subject: Re: Shapes From Shading? (was: Re: Martian Mystery?) In article <9102211652.AA08913@gemini.arc.nasa.gov>, greer%utdssa.dnet%utaivc@utspan.span.nasa.gov writes: > But there are people who have worked and are working on this > problem, mainly in the area of computer vision. I found a book in the UTD > library about computer vision called _From Pixels To Predicates_, edited > by Alex Pentland, which has a chapter about infering shapes from shading. > Also, what about _Mars: The Movie_, _Miranda: The Movie_, and _LA (you > guessed it): The Movie_. Those weren't all produced from stereographic > pairs were they? Maybe someone from JPL can tell us about shading to > shape inference I didn't work on these movies, but I attended a technical presentation about them a couple of years ago. They use a combination of altitude data (where available) and photoclinometry (like you said, figuring out shape from shading). I never heard any mention of using stereographic information to construct terrain models. -- This is news. This is your | Peter Scott, NASA/JPL/Caltech brain on news. Any questions? | (pjs@euclid.jpl.nasa.gov) ------------------------------ Date: 22 Feb 91 20:54:44 GMT From: borg!vangogh!leech@mcnc.org (Jonathan Leech) Subject: Re: Terraforming, sun shield In article <1991Feb22.184557.18844@bradley.bradley.edu>, moonman@buhub.bradley.edu (Craig Levin) writes: |> Could one use close approaches by minor planets or comets to |> somehow plow off the atmosphere? I mean, if we're at a level where |> you're considering huge sheets of Mylar up there, we can definitely |> tug around a few comets here and there. This has been restricted to sci.space due to lack of relevance to sci.{optics,physics}. Assuming I didn't drop any decimal points below, it would be difficult. For handwaving purposes, let's say we can couple 100% of the kinetic energy of a cometary impact to the atmosphere, and there are no hydrodynamic losses. Then the mass of Venus' atmosphere is ~(9*10^4 gm/cm^2)(4 pi (6*10^8 cm)^2) = 4*10^23 gm. Escape velocity is ~10 km/sec and if we assume a mean impact velocity of 20 km/sec (should be somewhat higher, that figure is for Earth-crossing asteroids), we need 1/4 that mass of comet or 10^23 gm. Assuming iceballs at 1 gm/cm^3 - actually much lower - we need one comet ~300km in radius (we actually want glancing impacts with a whole bunch of smaller ones, I think). In reality the coupling is going to be inefficient, so much more mass would be needed. So this technique doesn't look too useful unless we can move Chiron-sized objects around or have a lot of time and energy to spend chasing down small comets. Personally I can think of better uses for comets and asteroids than wasting them on making a tropical sauna planet, but maybe we could give Venus it's own moon while we're at it :-) -- Jon Leech (leech@cs.unc.edu) __@/ ``Even by the 22nd century, no way had yet been discovered of keeping elderly and conservative scientists from occupying crucial administrative positions. Indeed, it was doubted if the problem ever would be solved.'' - Arthur Clarke, _Rendezvous with Rama_ ------------------------------ Date: 22 Feb 91 21:10:48 GMT From: swrinde!cs.utexas.edu!news-server.csri.toronto.edu!utzoo!henry@ucsd.edu (Henry Spencer) Subject: Re: Terraforming, sun shield In article <1991Feb22.184557.18844@bradley.bradley.edu> moonman@buhub.bradley.edu (Craig Levin) writes: > Could one use close approaches by minor planets or comets to >somehow plow off the atmosphere? ... I saw a paper in JBIS proposing impacts by the largest half-dozen asteroids, to simultaneously blast off a fair bit of the atmosphere and spin up the planet (its rotation is annoyingly slow). My dim recollection is that the blast-off scheme does not, in fact, work as well as the authors proposed. It's really hard to get rid of 90atm of gas around an Earth-sized planet. -- "Read the OSI protocol specifications? | Henry Spencer @ U of Toronto Zoology I can't even *lift* them!" | henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 22 Feb 91 19:24:38 GMT From: tardis@athena.mit.edu (Ronald G Lovejoy) Subject: Re: Terraforming, sun shield In article <1991Feb22.164032.16901@zoo.toronto.edu>, henry@zoo.toronto.edu (Henry Spencer) writes: |> In article <5705@optilink.UUCP> cramer@optilink.UUCP (Clayton Cramer) writes: |> >... Try big dirigibles in the upper atmosphere, carrying algae |> >to do the CO2 -> O2 conversion. Much more practical. |> |> Well, not really, if what you want is a habitable planet. If you think |> 90 atmospheres of CO2 with clouds made of sulfuric acid droplets is a |> hostile environment, 90 atmospheres of *oxygen* has it beat in spades. |> High-pressure oxygen is corrosive almost beyond imagining, especially |> when hot. The real problem with terraforming Venus, far more significant |> than the shortage of water or the nearness to the Sun, is the need to get |> rid of most of the atmosphere somehow. I'm not sure that that's really much of a problem. CO2 is a heavier gas than O2 and since Venus and Earth have about the same mass (and Earth has 1 atmosphere of pressure), a lot of that liberated O2 may escape into space. Additionally, when these microorganisms take in the carbon and some of the sulfur, a lot of it will percipitate out of the atmosphere, thereby reducing the atmospheric mass some more. One possibility for solving the water problem may lie with the sulfuric acid. Although I haven't had any Chemistry since my freshman year, I understand that acids should have a hydrogen radical. By seperating out the hydrogen and combining it with oxygen, one can supply the water needed for the algae. Also, there should be some hydrogen locked up in the rocks on the surface. This particular discussion seems to be getting away from the actual focus of this group, so how about a new newsgroup, sci.terraform? Ron Lovejoy tardis@athena.mit.edu ------------------------------ End of SPACE Digest V13 #193 *******************