Check out Nick Hoffman's White Mars website.
Nick is a geophysicist at the University of Melbourne, with past experience in oil geology and several other areas; he contends that Mars has always been cold and dry, and that the fluid erosion so dramatically visible on the surface is due not to liquid water but to carbon dioxide — in both fluid and turbidity flows (he uses the term "cryoclastic flows", in analogy with the pyroclastic flows so familiar with terrestrial volcanos; what makes them active over longer distances on Mars is the continual addition of fresh gas from the entrained solid and liquid CO2 components). The concept also naturally explains the prevalent layering on Mars, in ways sedimentary rock can't.
While we'd all love to see a warm Mars, especially one which had developed
life
(and preferably one which still had relict life), Nick's arguments are persuasive;
the cold, dry picture fits much better than the other ones, which
have tremendous problems in explaining where all that water went (in the
White Mars scenario, the water is right where it's always been: frozen in
the crust), why the amount of carbonate rocks is so small, and why the
currently-active flow gullies are formed on the cold side of the cliffs in
the martian arctic (rather than nearer the equator, on the sunlit sides).
And then there's Philip Christensen's (of Arizona State University) recent observation of olivine layers at the base of Valles Marineris, some 4.5 km below ground surface. These olivines quickly rust away when exposed to liquid water, yet they are preserved here after ~3 billion years. Therefore, the crust of Mars must have been frozen at this (equatorial) location for all of the last 3 billion years, to a depth of at least 4.5 km.
Recent statements from NASA appear to support the White Mars picture. This was also recently discussed on VodkaPundit. Don't miss Robin Goodfellow's interesting remarks in the comments section.
Submitted by: Posse member Troy Loney
What are the implications of this theory for atmosphere loss? I recall that the main claims for a "warm" Mars in the first place was a much denser atmosphere (with a considerable quantity of CO2 and H2O) capable of retaining heat. Given that the H2O seems to be missing, we still have CO2. Does the "White Mars" theory rule out a warm but very dry Mars at some point in the distant past?
Posted by: Karl Hallowell at August 26, 2003 01:10 PMKarl, as Nick Hoffman explains on his "White Mars" website, there are few reasons to suppose that Mars' atmosphere was ever very dense, at least not for very long. The young sun was fainter than at present, and the crater record on Mars extends back at least 3.5 billion years, in many cases with little erosion; it's entirely possible that Mars' CO2 froze out early on, and even when some was liberated by a large impact, it froze out again in short order (a substantial fraction of the present atmosphere freezes out onto the polar caps each winter... even with the stronger sun).
IIRC the origin of the claim that Mars once had a thick wet atmosphere was to provide enough warming that the fluid-erosion features could have been made by liquid water; Hoffman suggests they were made by CO2 flows instead, which removes the need for the extreme (and otherwise unsubstantiated) "thick" early atmosphere. Read his site; it's fascinating.
Posted by: Troy at August 27, 2003 01:32 AMAnother question. The white Mars theory would indicate that the conditions for CO2 based debris flow erosion are still present. Hence, we should be able to see recent evidence of this sort of erosion. Is there any evidence say in the giant canyons or elsewhere to indicate that this erosion process is still going on?
Posted by: Karl Hallowell at August 28, 2003 04:56 PMYep. The polar gullies which Malin and others have attributed to flowing water are presently active, but Hoffman has demonstrated that temperatures at the time of their activity are too low for water to be the fluid. Again, this is from Nick Hoffman's "White Mars" website -- the whole thing is worth reading!
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