A team of researchers, using NASA’s Curiosity rover’s ChemCam instrument, made a fascinating discovery on Mars within Gale Crater: higher-than-usual levels of manganese in lakebed rocks. Published in the Journal of Geophysical Research: Planets, this finding suggests that the sediments were formed in a river, delta, or near the shoreline of an ancient lake.
Patrick Gasda, from Los Alamos National Laboratory’s Space Science and Applications group and lead author of the study, expressed surprise at the presence of manganese oxide in such concentrations in a shoreline deposit on Mars. On Earth, similar deposits are common due to the oxygen in our atmosphere, produced by photosynthetic life and microbes that catalyze manganese oxidation reactions. However, the mechanism for manganese oxide formation on Mars, where evidence for life is lacking and oxygen production is unclear, remains puzzling.
ChemCam, developed by Los Alamos and CNES, employs a laser to create a plasma on rock surfaces, allowing for the quantification of elemental composition. The sedimentary rocks studied by Curiosity consist of sands, silts, and muds, with sandy rocks being more porous. The research team explored how groundwater could have enriched manganese in these sands, such as through percolation along the shore of a lake or at the mouth of a delta, and what oxidant might have precipitated manganese in the rocks.
On Earth, manganese enrichment occurs due to atmospheric oxygen, often accelerated by microbial presence. This process can serve as an energy source for metabolism in microbes. Nina Lanza, principal investigator for the ChemCam instrument, noted that the Gale lake environment depicted by these ancient rocks resembles habitable environments on Earth today, where manganese minerals are common in shallow, oxygen-rich waters found on lake shores.
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Journal Reference:
- P. J. Gasda, N. L. Lanza, P.‐Y. Meslin, S. N. Lamm, A. Cousin, R. Anderson, O. Forni, E. Swanner, J. L’Haridon, J. Frydenvang, N. Thomas, S. Gwizd, N. Stein, W. W. Fischer, J. Hurowitz, D. Sumner, F. Rivera‐Hernández, L. Crossey, A. Ollila, A. Essunfeld, H. E. Newsom, B. Clark, R. C. Wiens, O. Gasnault, S. M. Clegg, S. Maurice, D. Delapp, A. Reyes‐Newell. Manganese‐Rich Sandstones as an Indicator of Ancient Oxic Lake Water Conditions in Gale Crater, Mars. Journal of Geophysical Research: Planets, 2024; 129 (5) DOI: 10.1029/2023JE007923