Higher-than-usual levels of manganese were found in lakebed rocks within Gale Crater on Mars by a study team utilizing the ChemCam instrument on NASA’s Curiosity rover. This finding suggests that the sediments were generated in a river, delta, or close to the coastline of an old lake. Today’s Journal of Geophysical Research: Planets published the findings

Lead author Patrick Gasda of Los Alamos National Laboratory’s Space Science and Applications group stated, “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,”  “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.

“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. 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,” More research is necessary to fully comprehend oxidation on Mars, as these findings suggest more significant processes taking place in the Martian atmosphere or surface water, according to Gasda.

In order to measure the elemental makeup of rocks, ChemCam, a technology developed at Los Alamos and the French space agency CNES, forms a plasma on a rock’s surface using a laser and then gathers light from it.

The rover has been studying a variety of sands, silts, and mud-like sedimentary rocks. When compared to the muds that comprise the majority of the lakebed rocks in the Gale Crater, sands are more porous and allow groundwater to travel through them more readily. The research team examined what oxidant might have caused the manganese to precipitate in the rocks and how manganese could have been enhanced in these sands—for instance, by groundwater percolating through the sands on a lakeshore or delta mouth.

The presence of bacteria frequently speeds up the process by which oxygen in the atmosphere enriches manganese on Earth. The enhanced manganese content in these rocks along the lakeshore would have been a useful energy source for life if it had existed on ancient Mars. Microbes on Earth may use the various oxidation states of manganese as energy for metabolism.

“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,” “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.”