I looked through several of the 2012 LPSC abstracts on the MSL landing site at Gale Crater and was struck by the Niles and Michalski paper (http://www.lpi.usra.edu/meetings/lpsc2012/pdf/2575.pdf.)
An unstated implication of their hypothesis is that the phyllosilicates (clay minerals) at the base of the mound may have formed by brines percolating through the mound. If so, then the clay-bearing “beds” detected by CRISM (reported by Miliken et al., 2010, http://www.agu.org/pubs/crossref/2010/2009GL041870.shtml [abstract only]) may not be recording climate conditions of very ancient Mars (when neutral or alkaline surface water was presumably abundant) but a secondary alteration of (basaltic?) materials at a later time. So, it seems there’s some question as to whether Curiosity will actually be examining clays that date from a more clement and habitable period of Mars’ history. It may be that the clays at Gale formed around the same time as the sediments at Meridiani—a period when surface water was generally acidic and much less common.
I’m sure this observation is nothing new to those “in the loop,” but it was a revelation to me. Hopefully, Curiosity will be able to determine the true origin of these clays. I guess I’m preparing myself just in case the press reports “disappointing” results from Curiosity sometime next year.
Tom
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