This self-portrait of NASA's Curiosity Mars rover shows the vehicle at the "Quela" drilling location in the "Murray Buttes" area on lower Mount Sharp.NASA/JPL–CALTECH/MSSS
NASA’s Curiosity rover has collected samples on Mars that show an excess of carbon-12 compared to carbon-13. The finding was reported in the paper, “Depleted carbon isotope compositions observed at Gale crater, Mars,” published in the Proceedings of the National Academy of Sciences (PNAS).
On Earth, the global carbon cycle describes how this element cycles through different reservoirs at a planetary scale, from the atmosphere to the oceans, and through rocks and even living organisms. Isotopic changes in carbon atoms can be a signature of the processes that carbon goes through in this cycling. Sometimes on Earth, an excess of carbon-12 has been interpreted as a ‘signature’ of ancient life when it appears alongside other features, such as geological formations that indicate possible ancient microbial mats, or the presence of diverse and complex organic molecules formed by life.
On Mars, those additional features haven’t been identified, and the processes leading to an excess of carbon-12 are very different. In the recent publication, the authors discuss three plausible explanations for Curiosity’s findings: cosmic dust, the photoreduction of carbon dioxide, and photolysis of methane produced by biology. Each of these explanations is unconventional compared to what we see on Earth, and only one would have involved life. Further information about the martian environment would be needed to determine if any of the three scenarios could explain the results.
A recent post by Many Worlds discusses Curiosity’s findings and how they are helping astrobiologists better understand the history of the martian environment and the potential for life in the planet’s past. To read the full post, visit:
https://manyworlds.space/2022/01/22/tantalizing-carbon-signals-from-mars/
Related Links:
NASA’s Curiosity Rover Measures Intriguing Carbon Signature on Mars
The Many Worlds Blog chronicles the search for evidence of life beyond Earth written by author/journalist Marc Kaufman. The “Many Worlds” column is supported by the Lunar Planetary Institute/USRA and informed by NASA’s NExSS initiative, a research coordination network supported by the NASA Astrobiology Program. Any opinions expressed are the author’s alone.