Reflectance of Jezero Crater Floor: 2. Mineralogical Interpretation

The Perseverance rover landed in the ancient lakebed of Jezero crater, Mars on February 2021. Here, we assess the mineralogy of the rocks, regolith, and dust measured during the first year of the mission on the crater floor, using the visible and near-infrared spectrometer of SuperCam onboard the Perseverance rover. Most of the minerals detected from orbit are present in the bedrock, with olivine-bearing rocks at the bottom of the stratigraphy and high-Ca pyroxene-bearing rocks at the top. This is distinct from the overall low-Ca pyroxene-bearing composition of the watershed of Jezero and points toward an igneous origin. Alteration mineral phases were detected in most of the rocks analyzed in low proportions, suggesting that aqueous alteration of the crater floor has been spatially widespread, but limited in intensity and/or time. The diverse aqueous mineralogy suggests that the aqueous alteration history of the crater floor consists of at least two stages, to form phyllosilicates and oxyhydroxides, and later sulfates. We interpret their formation in a lake or under deeper serpentinization conditions and in an evaporative environment, respectively. Spectral similarities of dust with some rock coatings suggest widespread past processes of dust induration under liquid water activity late in the history of Jezero. Analysis of the regolith revealed some local inputs from the surrounding rocks. Relevant to the Mars Sample Return mission, the spectral features exhibited by the rocks sampled on the crater floor are representative of the diversity of spectra measured on the geological units investigated by the rover. Plain Language Summary We present the results of the analysis of rocks and regolith measured during the first year after landing of the Perseverance rover on Mars. The analytical technique used is reflectance spectroscopy (the measurement of the light reflected by surfaces), which primarily provides information on mineralogy. The mineralogical composition of the magmatic rocks located near the landing site indicates that they have experienced several distinct episodes of interaction with water in the past, of relatively low intensity. Soil analysis reveals a composition similar to what has been observed at other sites on Mars, with a contribution from the disintegration of local rocks. The samples that are collected by Perseverance at the crater floor and brought back to Earth are representative of the diversity of the different geological units explored by the rover.