Carbonated ultramafic rocks in Jezero crater, Mars

Rocks explored by the Perseverance rover during a ten-kilometer traverse along the inner rim of Jezero crater, Mars consist of coarse-grained olivine, Mg-Fe carbonate, silica, and phyllosilicates. These rocks span more than 400meters in elevation, from beneath the western sedimentary fan to the upper crater rim, and are among the oldest materials exposed within Jezero. Compositions including extremely low calcium and aluminum contents suggest formation by olivine accumulation in a system of layered intrusions followed by extensive alteration by carbonation in the presence of liquid water and atmospheric carbon dioxide. Carbonation was likely enhanced by the lake system at lower elevations. Higher elevation exposures on the crater rim suggest affinity with olivine-rich rocks distributed over a vast area in the Nili Fossae region.