Carbonates of iron-magnesium on the surface of Mars

NASA's Mars Exploration Rover Spirit has obtained some significant data on the detailed chemical composition of the rock exposed on the ground surface of the Columbia Hills of the Gusev crater. It was found that the rock is a Mg-Fe carbonate (Mc_0.62Sd_0.25Cc_0.11Rh_0.02, where Mc = magnesite, Sd = siderite, Cc = calcite, and Rh = rhodochrosite) and a forsteritic olivine (Fo_0.72Fa_0.28, where Fo = forsterite and Fa = fayalite). This could suggest extensive aqueous activity under near-neutral pH conditions that would be conducive to habitable environments on early Mars. On this occasion, in addition to a X-ray spectrometer, a Mossbauer (MB) spectrometer and Miniature Thermal Emission Spectrometer (Mini-TES) greatly contributed to the findings. For more information, see the paper, "Identification of Carbonate-Rich Outcrops on Mars by the Spirit Rover", R. V. Morris et al., Science 329, 421 (2010).