Identification of Carbonate-Rich Outcrops on Mars by the Spirit Rover

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Science  03 Jun 2010:
DOI: 10.1126/science.1189667


Decades of speculation about a warmer, wetter Mars climate in the planet's first billion years call upon a denser CO2-rich atmosphere than at present. Such an atmosphere should have led to the formation of outcrops rich in carbonate minerals, for which evidence has been sparse. Using the Mars Exploration Rover (MER) Spirit, we have now identified outcrops rich in Mg-Fe carbonate (16 to 34 wt.%) in the Columbia Hills of Gusev crater. Its composition approximates the average composition of the carbonate globules in Martian meteorite ALH 84001. The Gusev carbonate probably precipitated from carbonate-bearing solutions under hydrothermal conditions at near-neutral pH in association with volcanic activity during the Noachian era