Redox-Driven Mineral and Organic Associations in Jezero Crater, Mars

The Perseverance rover has explored and sampled igneous and sedimentary rocks within Jezero crater to characterize early Martian geological processes and habitability and search for potential biosignatures7. Upon entering Neretva Vallis, on Jezero crater’s western edge, Perseverance investigated distinctive mudstone and conglomerate outcrops of the Bright Angel formation. Here we report a detailed geological, petrographic, and geochemical survey of these rocks and show that organic carbon bearing mudstones in the Bright Angel formation contain sub-millimeter-scale nodules and mm-scale reaction fronts enriched in ferrous iron phosphate and sulfide minerals, likely vivianite and greigite, respectively. This organic carbon appears to have participated in post-depositional redox reactions that produced the observed Fe-phosphate and Fe-sulfide minerals. Geological context and petrography indicate that these reactions occurred at low temperatures. Within this context, we review the various pathways by which redox reactions that involve organic matter can produce the observed suite of Fe-, S-, and P-bearing minerals in laboratory and natural environments on Earth. Ultimately, we conclude that analysis of the core sample collected from this unit using high-sensitivity instrumentation on Earth will enable the measurements required to determine the origin of the minerals, organics, and textures it contains.