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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:

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----------------------------------------------------------------------

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![e-mail]  (Henry Spencer)
Subject: Re: Terraforming, sun shield

In article <[e-mail]> [e-mail] (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!"              |  [e-mail]  utzoo!henry

------------------------------

Date: 22 Feb 91 01:44:38 GMT
From: sdd.hp.com!news.cs.indiana.edu!ux1.cso.uiuc.edu![e-mail]  (Doug McDonald)
Subject: Re: Commercially-funded Space Probes (was Re: Space Profits)


In article <[e-mail]> [e-mail] (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![e-mail]  (Eddie A. McCreary)
Subject: Re: Shapes From Shading? (was: Re: Martian Mystery?)

In article <[e-mail]>, [e-mail] 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
[e-mail], 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![e-mail]  (Henry Spencer)
Subject: Re: Terraforming, sun shield

In article <[e-mail]> [e-mail] (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!"              |  [e-mail]  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![e-mail]  (Chris Hall)
Subject: Re: Terraforming, sun shield

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>In article <[e-mail]> [e-mail] (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: [e-mail]

------------------------------

Date: 22 Feb 91 17:13:46 GMT
From: haven!ncifcrf!fcs260c2![e-mail]  (Tom Schneider)
Subject: Re: Terraforming, sun shield

In article <[e-mail]> [e-mail] (Clayton Cramer) writes:
>In article <[e-mail]>, [e-mail]
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
  [e-mail]

------------------------------

Date: 22 Feb 91 20:03:21 GMT
From: borg!vangogh![e-mail]  (Jonathan Leech)
Subject: Re: Shapes From Shading? (was: Re: Martian Mystery?)


In article <[e-mail]>,
[e-mail] (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 ([e-mail])    __@/
    "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![e-mail]  (Henry Spencer)
Subject: Re: Commercially-funded Space Probes (was Re: Space Profits)

In article <[e-mail]> [e-mail] (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!"              |  [e-mail]  utzoo!henry

------------------------------

Date: 22 Feb 91 18:26:00 GMT
From: swrinde!elroy.jpl.nasa.gov!euclid.jpl.nasa.gov![e-mail]  (Peter Scott)
Subject: Re: Shapes From Shading? (was: Re: Martian Mystery?)

In article <[e-mail]>, [e-mail] 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?    |    ([e-mail])

------------------------------

Date: 22 Feb 91 20:54:44 GMT
From: borg!vangogh![e-mail]  (Jonathan Leech)
Subject: Re: Terraforming, sun shield


In article <[e-mail]>,
[e-mail] (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 ([e-mail])    __@/
    ``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![e-mail]  (Henry Spencer)
Subject: Re: Terraforming, sun shield

In article <[e-mail]> [e-mail] (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!"              |  [e-mail]  utzoo!henry

------------------------------

Date: 22 Feb 91 19:24:38 GMT
From: [e-mail]  (Ronald G Lovejoy)
Subject: Re: Terraforming, sun shield

In article <[e-mail]>, [e-mail] (Henry Spencer) writes:
|> In article <[e-mail]> [e-mail] (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
[e-mail]

------------------------------

End of SPACE Digest V13 #193
*******************