Mineralogically Diverse and Salt-Rich Regolith in Jezero Crater Characterized Using X-Ray Spectroscopy

The Planetary Instrument for X-ray Lithochemistry (PIXL) onboard the Perseverance rover has characterized the composition of Martian regolith at a scale of hundreds of microns using micro-focus X-ray fluorescence spectroscopy. PIXL data reveal a diverse population of regolith grains with distinct spectral, chemical, and crystallographic properties, through which we identified the mineralogy of individual regolith components. Olivine, phyllosilicate, carbonate-bearing phases, Cr-Ti-spinel, plagioclase, and Fe-sulfate are all inferred from the data, and potential local and regional bedrock sources are proposed for each. PIXL also inspected dust and soil components, which were found to be geochemically similar to analogous components characterized elsewhere by preceding missions. Unlike other sites, regolith on the western fan front of Jezero crater contains fewer sulfates, but is highly enriched in Cl (up to 2.0 ± 0.5 wt. %), which likely includes chlorides, chlorates, and/or perchlorates. PIXL also finds evidence of hydration in the regolith, potentially carried by salts, as interstitial water, and/or in adsorbed phases. PIXL's observations of diverse amorphous and crystalline components, multiple styles of aqueous alteration, and enrichments of brine-forming salts provide exciting new justification for the return of a Martian regolith sample to Earth for further study.