Mars's quintessential "alienness" and go from there. Up till very recently we've been dealing (sometimes very acrimoniously) with concepts based on water and/or carbon dioxide. No doubt both have played and now play an important role, but recent results strongly suggest those aren't the only substances we should be concerned with.

The various acids and aqueous solutions we're considering now -- but essentially never thought of more than peripherally earlier -- may provide us with the beginnings of a comprehensive understanding, or may not. Something else again may prove more instructive.

Salt-water/acid solutions that could stay fluid at very low temperatures are certainly worth more than passing consideration.

Given conditions we see now and can extrapolate into the past, I'm reluctant to put too much stock in rain of any sort, although snow seems to be relatively widespread. Or rather "snows" since there seem to be a variety of substances snowing out depending on temperatures...

That doesn't preclude rain (acid rain or otherwise) under some conditions.

At one point, I wondered whether the sulfate deposits were being dissolved at the present time and wondered how a frigid carbon dioxide atmosphere might accomplish such dissolution. The beaded edges of the layers were among the signs of possible dissolution. Was the radiation enviornment participating in the dissolution? I wondered about the possibility the deposits were dissolving because there was so little erosion debris.

Comes now the Pot o Gold formation, and the appearance of dissolution as opposed to erosion is about as spectacular as one could ask for. Or are we looking at something that precipitated out in a fluid environment? Or did it grow much as we see it now?

Endless fascination.

Cheers, BRFelix