[X] My Assistant

[dvandorn]

As we all know, Martian meteorite ALH84001 has interesting structures that have now been debated endlessly as to their origins. The more interesting point, however, is that these structures occur within carbonate inclusions in the rock.

Carbonate Martian rocks have generally not been found from orbit by remote sensing equipment. And in ALH84001, the carbonate "nuggets" are rather tiny inclusions.

If there *are* carbonate rocks on Mars, how the heck do we find them? And if they tend to exist merely as tiny inclusions in other rocks, how do we analyze them (or even see that they're there) in situ?

-the other Doug

[dvandorn]

Well.

We seem to have, if not an answer, at least more information. Carbonates have been detected via evolved gas analysis by TEGA and by their distinctive crystalline structures in the only useful AFM image I've seen. They seem to be tiny grains in the soil (at least in the soils at the Phoenix site), and make up (if I heard the quote correctly) something like 6% of the samples analyzed.

So, we now have direct evidence of both the presence of carbonates and of their current structural state in the regolith. I understand the perils of globally generalizing to multiple soils based on what is seen at this admittedly non-representative location... but we're seeing enough carbonates here to at least start asking questions like:

A. How much carbonate rock is ground up into the soils of Mars?

B. For a given range of estimates of (A.) above, how much carbonate rock would have to have been emplaced and subsequently eroded into dust to account for the total mass? (i.e., are we talking about massive deposits from large ocean beds, or small emplacements in scattered lakes and small seas? Or just a few scattered crater lakes here and there?)

C. For a given range of estimates of (B.) above, and with a given range of atmospheric models, how much standing water had to have been available to form the estimated mass of carbonates, and for how long did the standing water have to persist to form that mass?

D. To what degree would a competing sulfur dioxide cycle have modified the known terrestrial example of carbonate formation?

I, for one, would feel comfortable designing a lander (or series of landers) designed to give us enough information to start answering those questions. And I think these are important questions in understanding the climate history of Mars.

-the other Doug