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 will provide important constraints on the petrologic history, aqueous processes, and timing of key events in Jezero. However, interpreting these samples will require 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, RIMFAX 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.

Juan Manuel Madariaga

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The SuperCam instrument onboard Perseverance rover has remote imaging (RMI), VISIR, LIBS, Raman and Time-Resolved Luminescence (TRL) capabilities. RMI images of the rocks at the Octavia Butler landing site have revealed important granular texture diversities. VISIR raster point observations have revealed important differences in the 2.10-2.50 µm infrared range (metal-hydroxides); many include water features at 1.40±0.04 and 1.92±0.02 µm [1]. LIBS observations on the same points analyzed by VISIR revealed important differences in the concentrations of major elements, suggesting mineral grain sizes larger than the laser beam (300-500 µm). LIBS and VISIR show coherent results in some rock surfaces that are consistent with an oxy-hydroxide (e.g., ferrihydrite) [1]. LIBS elemental compositions are consistent with pyroxenes, feldspars, and more often feldspar-like glass, often enriched in silica. Olivine compositions [1, 2] have been observed so far in LIBS data (up to Sol 140) exclusively in rounded regolith pebbles. They have not yet been observed in the rocks themselves, which are MgO-poor compared to regolith and are consistent with FeO bearing pyroxenes (e.g., hedenbergite, ferrosilite). A 3x3 LIBS and VISIR raster (9x9 mm) acquired on a low-standing rock on sol 90 exemplifies these finding. A dark L-shaped filled void sampled by points 1 and 2 with possible ferrihydrite (H seen in LIBS and VISIR spectra). Point 5 contains abundant silica and alkali elements but is Al-depleted relative to feldspars, consistent with dacitic glass composition. Point 7 has TiO2 content consistent with ilmenite. Comparisons to (igneous) Martian meteorites are potentially useful, e.g. [3], to explain the presence of several minerals, although most Martian meteorites are olivine-rich, e.g., more mafic than the rocks at the landing site. In summary, the bedrock at Octavia Butler landing site can be interpreted as showing evidence for relatively coarse-grained weathered pyroxenes, iron and titanium oxides and feldspars, while the local soil contains pebbles from a different source (richer in MgO) incorporating olivine grains. References: [1] Mandon et al. 2021 Fall AGU, New Orleans, LA, 13-17 Dec. ; [2] Beyssac et al. 2021 Fall AGU, New Orleans, LA, 13-17 Dec. ; [3] Garcia-Florentino et al.(2021), Talanta, 224, 121863.