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

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Science  23 Jul 2010:
Vol. 329, Issue 5990, pp. 421-424
DOI: 10.1126/science.1189667

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Ancient Carbonate Minerals on Mars

The historical presence of liquid water on Mars together with a CO 2-rich atmosphere should have resulted in the accumulation of large deposits of carbonate minerals. Yet, evidence for the presence of carbonates on the surface of Mars has been scarce. Using data collected by the Mars Exploration Rover, Spirit, Morris et al. (p. 421, published online 3 June; see the Perspective by Harvey) now present evidence for carbonate-rich outcrops in the Comanche outcrops within the Gusev crater. The carbonate is a major outcrop component and may have formed in the Noachian era (∼4 billion years ago) by precipitation from hydrothermal solutions that passed through buried carbonate deposits. Thus, it is likely that extensive aqueous activity under neutral pH conditions did occur on Mars.