A question basically for Nick Hoffman, or anyone else who has seriously thought about the "White Mars" paradigm.

As I understand it, Nick doesn't disagree that certain Martian features were cut by fluid erosion, but instead of water flow he argues they were due to catastrophic flows of CO2, either liquid or as dense, debris-laden gas flows (not unlike pyroclastic flows, I guess).

If any of the channels were cut by fluids, Mangala certainly looks like a good candidate, so I'm assuming Nick's theory would be that there was flow into Gusev in the past, but with CO2 as the fluid.

If so, I'm wondering how the deposits from CO2-charged debris flows should differ from water-derived sediments, or from aeolian depoits for that matter.

What features would distinguish sediments deposited from CO2 flows? I guess CO2 flows would be a high-energy environment so nice even silt layers would be unlikely, but can you say anything more detailed?

And, what about diagnostic minerals? Anything that you'd expect to find (or to not find) in material that has been weathered by liquid CO2? Does it react with rocks at all? I really don't have a sense for what it would do chemically.

If there are some papers that cover my questions feel free to point to them.

Of course, if there is no evidence for any sedimentation in Gusev (say it's all dust and regolith-covered lava flows), that's a problem for everyone, right? Hard to explain the valley otherwise. I recognize, though, that we might not find the relevant samples where we are. It'd sure be nice to look at those apparent delta remnants to the south.