A research team analyzing data from NASA’s Curiosity rover has made an intriguing discovery: unusually high levels of manganese in rocks within Gale Crater on Mars. This suggests that these sedimentary rocks were formed in a river, delta, or near the shoreline of an ancient lake. The findings, published today in the Journal of Geophysical Research: Planets, shed light on the Martian environment and raise questions about the planet’s past.
Lead author Patrick Gasda, from Los Alamos National Laboratory’s Space Science and Applications group, expressed surprise at the presence of manganese oxide in shoreline deposits on Mars. On Earth, such deposits are common due to the abundance of oxygen in our atmosphere, largely produced by photosynthetic life. However, without evidence of life on Mars and with uncertainty about oxygen production in its ancient atmosphere, the source of manganese oxide on the Red Planet remains puzzling.
The ChemCam instrument, developed by Los Alamos and CNES (the French space agency), played a crucial role in this discovery. By using a laser to create a plasma on the surface of a rock and analyzing the emitted light, ChemCam provided valuable data on the elemental composition of Martian rocks.
The sedimentary rocks studied by Curiosity are a mixture of sands, silts, and muds, with the sandy rocks being more porous. The research team investigated how manganese could have become concentrated in these sands, possibly through the percolation of groundwater in lake shores or delta mouths. They also considered potential oxidants responsible for manganese precipitation in the rocks.
On Earth, manganese enrichment is often linked to atmospheric oxygen, a process accelerated by microbial activity. If life existed on ancient Mars, the presence of manganese in these rocks could have served as an energy source for microbial metabolism.
Principal investigator Nina Lanza highlighted the similarities between the Gale lake environment on Mars and certain Earth habitats. Manganese minerals are commonly found in shallow, oxygen-rich waters along lake shores, mirroring conditions observed in Gale Crater.
The study, titled “Manganese-rich sandstones as an indicator of ancient oxic lake water conditions in Gale Crater, Mars,” was funded by NASA’s Jet Propulsion Laboratory.
