More than 185 bedrock targets examined by Perseverance in Jezero Crater’s Margin Unit show rocks were altered by water at least three times, pointing to a more complex Martian climate history.
Instead of the expected sedimentary shoreline deposits, the rover found igneous rocks whose minerals preserved separate water interactions, including carbon-dioxide-rich groundwater reacting with olivine to form carbonates.
Lower-elevation rocks below the apparent former waterline also contain silica, consistent with a later lake-related episode, while veins of calcium sulfate and fluorite indicate a third phase involving hotter underground water.
Those water-rock reactions could have produced hydrogen as a microbial energy source, and carbonate and silica may preserve chemical traces of ancient environments, sharpening Jezero’s importance in the search for past life.