The Perseverance rover surveyed rocks along a 10-kilometer track in Jezero Crater, covering 400 meters of elevation from the western sedimentary fan to the upper rim of the crater[1][2][3]. These rocks consist of coarse-grained olivine, magnesium and iron carbonates, sulfate, and phyllosilicates, including some of the oldest material in Jezero[1][2][3]. Olivine accumulated in the clay system of layered intrusions and was subsequently exposed to water and carbon dioxide, causing extensive carbonation of the silicate minerals[1][2][3]. Water alteration is more pronounced at lower elevations, while rocks at higher elevations on the rim of the crater resemble olivine rocks in the wider Nili Fossae area[1][2]. The Fe/Mg ratio in carbonates and olivine is similar, supporting in-situ carbonation, and there is evidence for multiple carbonate phases and hydrated minerals[1]. These observations show a complex alteration history including dissolution and reprecipitation[1].