In situ evidence for serpentinization within the Máaz formation, Jezero crater, Mars.

As both a source of atmospheric H2 and a sink for liquid water, the serpentinization of olivine-bearing rocks is widely thought to have influenced the long-term evolution of the early martian atmosphere and hydrosphere. However, the mechanisms, timing, and global importance of this process are unconstrained, in part because the remnants of ancient serpentinizing systems have not been examined in situ. New geochemical and mineralogical data from multiple instruments aboard the Mars 2020 Perseverance rover record serpentinization and associated H2 production in ancient igneous rocks of the Máaz formation, exposed on the Jezero crater floor. These data, combined with petrogenetic constraints, indicate that serpentinization may have been driven by devolatilization of magmatic H2O, highlighting a potential link between H2 production and the style and tempo of magmatism within the ancient martian crust.