Carbonates identified by the Curiosity rover indicate a carbon cycle operated on ancient Mars.
basic_science · Level V
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- Record sourced from PubMed, PMID 40245143.
- Also identified by DOI 10.1126/science.ado9966.
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Abstract
Ancient Mars had surface liquid water and a dense carbon dioxide (CO<sub>2</sub>)-rich atmosphere. Such an atmosphere would interact with crustal rocks, potentially leaving a mineralogical record of its presence. We analyzed the composition of an 89-meter stratigraphic section of Gale crater, Mars, using data collected by the Curiosity rover. An iron carbonate mineral, siderite, occurs in abundances of 4.8 to 10.5 weight %, colocated with highly water-soluble salts. We infer that the siderite formed in water-limited conditions, driven by water-rock reactions and evaporation. Comparison with orbital data indicates that similar strata (deposited globally) sequestered the equivalent of 2.6 to 36 millibar of atmospheric CO<sub>2</sub>. The presence of iron oxyhydroxides in these deposits indicates that a partially closed carbon cycle on ancient Mars returned some previously sequestered CO<sub>2</sub> to the atmosphere.