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Venus Radar Request, From Earth
Guest_BruceMoomaw_*
post Mar 9 2006, 01:03 AM
Post #16





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In reality, it wouldn't make a tinker's damn to Venus' chances of sustaining life whether it had a large moon or not -- its death warrant was signed the moment it formed close enough to the Sun to activate the "moist greenhouse" effect that stripped it of all its initial water and so allowed its volcanically released CO2 to build up and produce a huge blanket with a killer greenhouse effect.

Kevin Zahnle has an interesting new LPSC abstract ( http://www.lpi.usra.edu/meetings/lpsc2006/pdf/2359.pdf ) in which he claims that an Earthlike planet like Dune -- which started out with less water than Earth, but not NO water -- would actually be capable of sustaining a small biosphere much closer to the Sun than a planet which started out with a large water supply, because its moist-greenhouse effect would be minimal. However, he doesn't explain how that small initial amount of water could lock up most of the planet's CO2 in carbonate rocks, and thus why that planet wouldn't simply proceed to Venus' final fate much more directly. (Come to think of it, didn't we learn in the first Dune book that the planet actually had quite a bit of water overall, but the Little Makers sealed most of it off underground and prevented it from reaching the surface? If so, then before the Sandworms evolved -- since the Little Makers are their larval stage -- the planet must have been relatively wet and friendly. Kind of a reverse-Gaia effect.)
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Bob Shaw
post Mar 9 2006, 03:09 PM
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Bruce:

The Gaia effect - shorn of it's New Age mystical baggage - is just a handy catch all for homeostatic systems on a planetary environmental scale, so the Little Makers and the Sand Worms on Dune are simply ensuring that their environment suits their own needs, and in turn that environment has allowed them to fit it's paramaters. No real mystery there - except to the over-mystically inclined. Venus, however, is possibly a homeostatic system which has suffered catastrophic feedback and collapse to a more-or-less steady state which is quite inimical to life, and as such stands as a grim warning to us all regarding the changes we are wreaking on our own planet. Should we make the discovery of death (as opposed to the absence of life) on Venus then it should, I hope, have a profound effect on how we act here. I confess that I am rather concerned by our current effects on the Earth, not so much in terms of a few islands being drowned as a profound alteration to the whole environment (for example, as a result of clathrate decomposition in what was once tundra) and it'd be nice to have some changes made here and there before it's too late!

Bob Shaw


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AndyG
post Mar 9 2006, 04:01 PM
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QUOTE (Bob Shaw @ Mar 9 2006, 03:09 PM) *
Venus, however, is possibly a homeostatic system which has suffered catastrophic feedback and collapse to a more-or-less steady state which is quite inimical to life...

Perhaps on the surface - maybe not higher up the atmospheric column.

But that collapse of a system: is it due solely, as Bruce suggests, to the insolation received by the planet, or is it a deeper issue? If Venus had had a large Moon for example, and a higher rotation rate, and therefore more active tides and subsequent tectonic activity more akin to that of the Earth, wouldn't that have buried - sorry, sequestrated, to use the modern word ;-) - the excess CO2 efficiently?

The early Venus received 1800 watts per square metre compared to our 1380 today - that's not a huge difference compared to other locales in the Solar System. A spun-up Venus with a Moon might have been a suitable place for early life as well as the Earth.

(Perhaps I'm just hankering for the pre-probe SF Venus - dinosaurs wandering among the swampy jungles of our twin planet...)

Andy
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ljk4-1
post Mar 9 2006, 04:10 PM
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QUOTE (AndyG @ Mar 9 2006, 11:01 AM) *
(Perhaps I'm just hankering for the pre-probe SF Venus - dinosaurs wandering among the swampy jungles of our twin planet...)

Andy


So did the Soviets in the 1960s - they designed Venera 4 to float if it
came down upon a Venusian ocean!

http://www.hightechscience.org/venera-4_spacecraft_model.htm

http://www.kolumbus.fi/jimenez/photos/avaruus2000/


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"After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance.
I see that such intercourse long continued would make one thoroughly prosaic, hard,
and coarse. But the longest intercourse with Nature, though in her rudest moods, does
not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

- Henry David Thoreau, November 15, 1853

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Decepticon
post Mar 9 2006, 09:46 PM
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^Thanks for those Links!

Those models are so cool. cool.gif
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Gsnorgathon
post Mar 10 2006, 05:14 AM
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QUOTE (Bob Shaw @ Mar 9 2006, 03:09 PM) *
...
Should we make the discovery of death (as opposed to the absence of life) on Venus
...

Bob - that's absolute genius. I'd say it's beautiful, but somehow that doesn't seem quite the right word.
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JTN
post Mar 12 2006, 12:12 AM
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Going back to the subject of planetary radar: although they don't add much to the links already posted re Venus specifically, the following have some good material (eye candy!) for other objects:
http://www.naic.edu/~pradar/pradar.htm
http://www.naic.edu/~nolan/radar/
(more by Googling arecibo planetary radar or just "planetary radar")
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Decepticon
post Mar 12 2006, 12:29 AM
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Great links!

Going threw each one.
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Guest_DonPMitchell_*
post May 5 2006, 04:55 AM
Post #24





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QUOTE (ljk4-1 @ Mar 9 2006, 09:10 AM) *
So did the Soviets in the 1960s - they designed Venera 4 to float if it
came down upon a Venusian ocean!


Russian scientists mostly believed in the greenhouse theory. In the Venera-1 articles in Pravda, it describes a surface that is so hot that the rocks are "red hot". That must have been the official line from Keldysh. Lebedinsky did seem to believe in the ionospheric model, and proposed some varations of his own. He also believed in life on Mars, and installed a Sinton-band methane detector on Mars-1.

Actually, the Soviet radioastronomer Korol'kov was the first to measure microwave limb darkening of Venus (before Mariner-2), which he also interpreted as supporting the hot-surface theory.

The landers were made to float just as a contingancy.
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Guest_BruceMoomaw_*
post May 5 2006, 06:32 AM
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Yes -- remember that they were extensively insulated, which is why Venera-4 was standing up quite nicely to 280 deg C at the time air pressure crushed its hull.
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