The canyons of Mars

Super cool post over at Phil Plait's blog in regards to an oblique view of an exposed section in the Gale Crater on Mars, courtesy of NASA. This is some exciting stuff if you're a sed/strat nerd like me. Outcrops are the bread and butter of any geologist - unless you've got the money to drill cores or shoot seismic, subsurface geology is inferred from outcrops - and this one looks quite beautiful.

I just wish NASA would tell us a little more:

Layers near the bottom of the mound contain clay and sulfate minerals that indicate wet conditions. Overlying rock layers contain sulfates with little or no clay, consistent with these layers forming in an environment in which water was evaporating and Mars was drying out.

Since of course I'm immediately dying to know what sorts of clays, and which sulfate minerals. I'm thinking that when they're talking about sulfates consistent with Mars drying out, it'd be sulfate evaporites like gypsum, barite, or anhydrite. Which then allows my fevered imagination to bring forth images of the Paradox Formation in eastern Utah and Colorado.

Of course, I have to stop myself from getting carried away here. The Paradox Formation is in places thousands of feet thick and covers an enormous area, which is what allows it to have such a profound tectonic effect on the landscape. Looking at that outcrop, I'm having a hard time getting a sense of just how thick the evaporites would be, but probably not that much. But what it does say, about the existence of water on the surface of Mars in the past, is pretty huge. And of course - letting my imagination run just a little wild here - opens the possibility of more evaporite deposits lurking under the surface, and bigger ones, and somewhere out there, one of the salt tectonic guys is going, "squee!"