That must be a big plank in the argument against life having evolved on Mars. I can see some logic in that - on Earth, life has fixed Nitrogen into Nitrates and Amino Acids. Of course, Mars could be different. I do not know of any other possible mineral sinks for Nirtogen. Similarly, CO2 could only sink into carbonates. I had guessed incorrectly that Mars would have Nitrate somewhere, because on Earth, Nitrate and Sulfate are often associated.

I make speculative posts that often have little foundation in evidence. Some people are highly critical of this. My intent is just to stimulate some discussion, and maybe someone with the time to do more may incorporate some good point into a larger, well founded argument. That said...

I see the possibility that most of Mars is underlain by deep layers of sediments. The basalt regions could have deep seated sediments below, that are just not exposed. I think Mars may have had huge, planet smothering oceans the thickness of Earths crust, or more, not a paltry few miles deep. This ocean would have taken a long time to burn off in the Noachian, even with no magnetic field. The CO2 could have been taken up in this vast ocean, and exist in deep layers that are not exposed. Thinking: Carbonate precipitates before Sulfate, so if the bottom of the Valles Marineris is extensive Magnesium Sulfate layers (not just later hot spring deposits), then the Carbonate could be deeper, and not exposed. Only when much of the oceans had ablated would the sulfuric acid concentration go up and basalt be leached to form the Sulfates, etc.

Earth may have had more and much longer tectonism, but Mars possibly had these extensive and cataclysmic interactions of its atmosphere, extensive hydrosphere, and light element lithosphere. There may have been huge, planet wide depositions, leaching and alteration on great scales. Its the Shriveled Mars Theory.

A significant mass loss such as this would put Mars into a more distant orbit, no? Could it also result in axial instability? Is there any hard evidence for large mass loss?

A good link to recent developments:
http://www.spacedaily.com/news/mars-water-science-04d-printready.html