Mineral–Organic Associations in Jezero Crater Mudstones: Speculations on Ancient Martian Life

Recent analyses by NASA’s Perseverance rover have revealed centimeter-scale mineral and organic features in Jezero Crater mudstones that bear a striking resemblance to microbially mediated textures on Earth. A rock core from the Bright Angel Formation, informally named Cheyava Falls, contains “leopard spot” halos and “poppy-seed” nodules enriched in iron phosphate (vivianite) and iron sulfide (greigite), colocated with organic carbon. On Earth, these mineral assemblages commonly arise from microbial iron and sulfur cycling in anoxic sediments. While abiotic mechanisms are possible, the absence of thermal or acidic alteration in the sample makes such pathways less likely. Here, I review the rover’s observations, situate them within the context of Mars' paleoenvironment, and explore plausible metabolic analogs, including Fe(III) reduction, sulfate reduction, phosphite oxidation, and methanogenesis, that could have sustained an anaerobic microbial ecosystem in Jezero’s ancient lake. Also the implications for biosignature detection, astrobiological exploration, and panspermia, given the potential parallels between Martian and terrestrial biogeochemistry considered. Although definitive proof awaits sample return and laboratory study, the combined mineralogical, organic, and textural evidence strongly warrants classification of these features as potential biosignatures. This work highlights the importance of integrative analyses in evaluating life’s plausibility beyond Earth and underscores the need for continued investigation of Jezero’s sediments in the search for ancient Martian life.