re: Thoughts on The Opportunity Rocks...
I'd like to see what the mini-TES and APXS readings are for the subsurface of the bedrock material. If it suggests large amounts of sulfur all the way through, does that suggest sulfate? Might it be a volcanic ash deposit instead?
The news reports suggest there is still some debate among the scientists on the water vs. ash fall interpretation, which suggests there is still no slamdunk data on the issue.
If the APXS were to show carbon, I guess that would have to be carbonate though.
It it didn't? I think then that would be strong evidence the white near surface material widespread on Mars is probably either sulfate or an ash fall deposit.