Early geochemical environment of Mars as determined from thermodynamics of phyllosilicates

Alternative pasts for Mars There is abundant evidence that liquid water once existed on the surface of Mars. Today's martian atmosphere is too thin to sustain the sort of greenhouse effect that could create a climate warm enough to support liquid water but, one theory goes, there may have been a carbon dioxide-rich atmosphere in the past. The apparent absence of carbonates and the low escape rates of carbon dioxide, however, have argued against that explanation. Now a thermodynamic study of clay minerals recently discovered by the OMEGA spectro-imaging instrument on-board Mars Express, has provided a clearer picture of the primitive geochemical conditions on Mars. What emerges is an atmosphere with very low carbon dioxide levels. Other greenhouse gases — methane seems the most likely — may therefore have been involved in sustaining a warm and wet climate on Mars.