The UA-run Phoenix Mars Lander found evidence that the isotopic composition of atmospheric carbon dioxide is "pointing to an atmosphere rejuvenated by volcanic outpourings, possibly up to the very recent geologic past..." and "the atmosphere may have been chemically interacting with liquid water recently. And where there's liquid water, of course, there could be life." [right, ice in Phoenix Lander trench. Credit, UA/NASA]
A paper published today in the journal Science, co-authored by William Boynton and Dave Hamara at UA's Dept. of Planetary Sciences suggests that "low-temperature water-rock interaction has been dominant throughout martian history, carbonate formation is active and ongoing, and recent volcanic degassing has played a substantial role in the composition of the modern atmosphere."