Extensive carbonate deposits reported on Mars

According to a new paper published in Nature Geoscience, large deposits of carbonates have been found buried about six kilometres (four miles) below the surface of Leighton crater (exposed by the original impact), near the huge shield volcano in the Syrtis Major region. Small deposits have been found before on the surface, including recently by the rover Spirit, but much larger amounts would be additional evidence of a warmer, wetter ancient Mars, with a thicker atmosphere of carbon dioxide. Notably, carbonates are formed in non-acidic (alkaline) liquid water. So this finding would again reinforce the idea of ancient lakes, seas or oceans on the surface. But were those waters cold or warm? What about those icebergs? It seems like every time another piece of the puzzle is found, it just raises more questions…