Mineralogy, Morphology, and Emplacement History of the Maaz Formation on the Jezero Crater Floor From Orbital and Rover Observations

The first samples collected by the Perseverance rover on the Mars 2020 mission were from the Maaz formation, a lava plain that covers most of the floor of Jezero crater. Laboratory analysis of these samples back on Earth would provide important constraints on the petrologic history, aqueous processes, and timing of key events in Jezero crater. However, interpreting these samples requires a detailed understanding of the emplacement and modification history of the Maaz formation. Here we synthesize rover and orbital remote sensing data to link outcrop-scale interpretations to the broader history of the crater, including Mastcam-Z mosaics and multispectral images, SuperCam chemistry and reflectance point spectra, Radar Imager for Mars' subsurface eXperiment ground penetrating radar, and orbital hyperspectral reflectance and high-resolution images. We show that the Maaz formation is composed of a series of distinct members corresponding to basaltic to basaltic-andesite lava flows. The members exhibit variable spectral signatures dominated by high-Ca pyroxene, Fe-bearing feldspar, and hematite, which can be tied directly to igneous grains and altered matrix in abrasion patches. Spectral variations correlate with morphological variations, from recessive layers that produce a regolith lag in lower Maaz, to weathered polygonally fractured paleosurfaces and crater-retaining massive blocky hummocks in upper Maaz. The Maaz members were likely separated by one or more extended periods of time, and were subjected to variable erosion, burial, exhumation, weathering, and tectonic modification. The two unique samples from the Maaz formation are representative of this diversity, and together will provide an important geochronological framework for the history of Jezero crater.Plain Language Summary The Perseverance rover on the Mars 2020 mission is collecting samples from Jezero crater for potential return to Earth via Mars Sample Return, and the first samples collected by the rover were from the Maaz formation, a lava plain that covers much of the crater floor. These igneous samples can be used to date when the lavas crystallized and to better understand their subsequent interactions with water, both of which will be important for reconstructing the history of habitable environments in Jezero crater. In this study we use images and reflectance spectra from the rover and orbiters, along with ground penetrating radar from the rover, to determine the history of the Maaz formation lavas. We find evidence for significant erosion and weathering in between successive flows, suggesting that they were emplaced over a long period of time. Some of the lavas underlie the Jezero delta, and so their age will provide limits on the timing of lake activity in Jezero crater, while others retain craters, so their age will help to better understand crater density-based age estimates for surfaces across Mars.