At 12:07 PM 3/24/2004 +0900, Michael Turner wrote:
Not to be the killjoy troublemaker (who, me?), but what I mainly see in this announcement is evidence of *liquid* movement. Isn't "standing body of liquid" the safer hypothesis?
And what would that liquid be, if not water? Well, there is some scientist in Australia with alternative models of Mars that are much more CO2-based. In one of these models, Mars had, for a relatively brief epoch, a very dense CO2 atmosphere with liquid CO2 seas. Isn't it possible that evidence of water chemistry and evidence of CO2 fluid flow (both liquid and gaseous) could co-exist in the same environment, each from a different time, but with CO2 the main contributor to the larger-scale phenomena? (By the way, that's not a rhetorical question, because I'm not a planetary scientist. ;-)
The evidence for liquid is the layering data referred to in the quoted article. Over the past several weeks data has also been accumulated for the existence of several salts in the rocks. The salts would require water or some other ionic solvent. Carbon dioxide would never dissolve these minerals in the first place, so for them to be deposited, it could not have been the solvent. Water is far more likely to have occurred on the surface any likely past Mars than liquid CO2 in any case, ergo we assume that the liquid that made the layering pattern was water. The model going around JPL is that Meridiani was a kind of salt flat, like the Great Salt Lake, where mineral-laden water evaporated and was replaced by more mineral-laden water, creating layers of salty sediment deposit. This explains the salts and cross-bedding nicely.
Gregg
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