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Earth-like environment likely on ancient Mars

  • May 9, 2024
  • 3 min read
Earth-like environment likely on ancient Mars

A team of researchers using the ChemCam instruments on NASA’s Curiosity rover found a higher-than-usual amount of manganese in lakebed rocks within the Gale Crater on Mars. This indicates that the sediments were once formed in a river delta or close to the shoreline of an ancient lake. The results were published in Journal of Geophysical Research: Planets.

“It is difficult for manganese oxide to form on the surface of Mars, so we didn’t expect to find it in such high concentrations in a shoreline deposit,” Patrick Gasda, of Los Alamos National Laboratory’s Space Science and Applications group and lead author on the study said. “On Earth, these types of deposits happen all the time because of the high oxygen in our atmosphere produced by photosynthetic life, and from microbes that help catalyze those manganese oxidation reactions.

ChemCam was developed at Los Alamos and CNES (the French space agency). It uses a laser to form a plasma on the rock surface, collecting the light to quantify elemental composition in rocks. The sedimentary rocks explored by the rover include sands, silts, and muds.

The sandy rocks are the most porous and groundwater can easily pass through sands than mud that make up the majority of the lakebed rocks in the crater.

“On Mars, we don’t have evidence for life, and the mechanism to produce oxygen in Mars’s ancient atmosphere is unclear, so how the manganese oxide was formed and concentrated here is really puzzling,” Gasda added. “These findings point to larger processes occurring in the Martian atmosphere or surface water and shows that more work needs to be done to understand oxidation on Mars.”

The team examined how the manganese could have been enriched in the sands. One way is the percolation of groundwater trough sands on the water, such as on the shore of a lake or the mouth of a river delta. They wanted to know what oxidant could be responsible for the precipitation of manganese in the rocks.

On Earth, manganese becomes enriched due to oxygen in the atmosphere. This process is accelerated by microorganisms. These microorganisms use the many oxidation states of manganese as energy for metabolism. If there was any life on an ancient Mars, the increased quantity of manganese in the rocks along the lake sshore would be a valuable resource for them.

“The Gale lake environment, as revealed by these ancient rocks, gives us a window into a habitable environment that looks surprisingly similar to places on Earth today,” said Nina Lanza, principal investigator for the ChemCam instrument. “Manganese minerals are common in the shallow, oxic waters found on lake shores on Earth, and it’s remarkable to find such recognizable features on ancient Mars.”

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