YAY! Check it out: http://gsa.confex.com/gsa/2002AM/finalprogram/abstract_36936.htm

Ever since sulfuric acid was recognized as a significant player in the deposits in Meridiani, I've wondered what sort of similarities and differences there might be between a more or less familiar "watery" environment on Mars and one that was highly acidic.

At the link above and at this link http://gsa.confex.com/gsa/2002AM/finalprogram/abstract_36934.htm
from the same conference -- and I'm sure there are more -- the topic is considered (c. 2002), based on such terrestrial analogies as are known, and on laboratory experiment. Cool.

Well, it turns out that a sulfuric acid enviornment would be characterized by an absence of carbonates which may begin to explain why there is apparently so little carbonate rock anywhere on Mars. Is it possible that pure or salty water is actually quite rare on Mars -- and has always been rare? Is it possible that the more prevalent fluid is not water at all but a sulfuric acid solution?

Although I'm not inclined to say that's what it is at this point, the question needs to be raised, and the consequences need to be considered.

Since there are acidophilic species on Earth, an acid fluid environment does not preclude the presence of biology on Mars, but if the typical solvent on Mars has always been sulfuric acid, not water, then we would have to think through how biology might originate in such a fluid, or how (in a panspermia model) life which originated in water can adapt to acidic planetary environments.

Particularly interesting for me are some findings about how sulfuric acid behaves as a surface fluid compared to water.

Among findings in the second cite above are the following:

• acid solutions act like fluidized sediment flows in which grains are carried on top of the liquid

• the acid solutions also contained unique depositional and syndepositional features. These include "crater" air bubbles and surface cracks developed due to the density of the acid solution.

• The features produced by the acid solutions in these experiments resemble features seen in photographs returned from Mars. For example, small craters on Martian alluvial fans look similar to crater air bubbles produced by acid flows

• Also, syndepositional cracks produced by experimental acid runs resemble mysterious cracks in photographed in the Nilo Syrtis region.

And this most interesting finding:

• It has been proposed that a 39% sulfuric acid solution would be a stable liquid on Mars’ surface today (Clark, 1994)

While I doubt sulfuric acid answers for everything, certainly a number of otherwise inexplicable features on the Martian surface (or explicable only by the most tortuous means) start to make some sense.

Reviewing our understanding of the surface in light of the presence and action of sulfuric acid might be well worthwhile...

Cheers, BRFelix