SciTechDaily
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NASA’s Curiosity rover landed on Mars on August 6, 2012, and since then has roamed Gale Crater taking samples and sending the results back home for researchers to interpret. Analysis of carbon isotopes in sediment samples taken from half a dozen exposed locations, including an exposed cliff, leave researchers with three plausible explanations for the carbon’s origin — cosmic dust, ultraviolet degradation of carbon dioxide, or ultraviolet degradation of biologically produced methane.
The researchers note today (January 17, 2022) in Proceedings of the National Academy of Sciences that “All three of these scenarios are unconventional, unlike processes common on Earth.”