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The Perseverance rover landed in Jezero crater, Mars, to investigate ancient lake and river deposits. We report observations of the crater floor, below the crater’s sedimentary delta, finding the floor consists of igneous rocks altered by water. The lowest exposed unit, informally named Séítah, is a coarsely crystalline olivine-rich rock, which accumulated at the base of a magma body. Fe-Mg carbonates along grain boundaries indicate reactions with CO 2 -rich water, under water-poor conditions. Overlying Séítah is a unit informally named Máaz, which we interpret as lava flows or the chemical complement to Séítah in a layered igneous body. Voids in these rocks contain sulfates and perchlorates, likely introduced by later near-surface brine evaporation. Core samples of these rocks were stored aboard Perseverance for potential return to Earth.

Before Perseverance, Jezero crater’s floor was variably hypothesized to have a lacustrine, lava, volcanic airfall, or aeolian origin. SuperCam observations in the first 286 Mars days on Mars revealed a volcanic and intrusive terrain with compositional and density stratification. The dominant lithology along the traverse is basaltic, with plagioclase enrichment in stratigraphically higher locations. Stratigraphically lower, layered rocks are richer in normative pyroxene. The lowest observed unit has the highest inferred density and is olivine-rich with coarse (1.5 millimeters) euhedral, relatively unweathered grains, suggesting a cumulate origin. This is the first martian cumulate and shows similarities to martian meteorites, which also express olivine disequilibrium. Alteration materials including carbonates, sulfates, perchlorates, hydrated silicates, and iron oxides are pervasive but low in abundance, suggesting relatively brief lacustrine conditions. Orbital observations link the Jezero floor lithology to the broader Nili-Syrtis region, suggesting that density-driven compositional stratification is a regional characteristic.

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Zinc oxide films of high optical quality have been deposited onto both silica and silicon substrates using reactive sputtering, pulsed laser deposition, and an aqueous solution based technique. Films have been characterized with respect to crystalline phase and phase stability, surface morphology, and optical response by means of Xray diffraction, Raman Spectroscopy, Atomic Force Microscopy, optical transmission and ellipsometry measurements. All films studied were of the wurtzite phase, finegrained, and exhibited varying degrees of c-axis orientation with respect to the substrate normal depending upon deposition conditions. Films showed s o m e degree of residual tensile stress which was inferred.from the E2 Raman line shift relative to the single crystal frequency. The wurtzite phase was found to be stable to temperatures near 800°C, but at highertemperatures, reaction with silica led to evolution of Zn2SiO4 at the interface. Variations in Raman line intensities upon post deposition annealing has been correlated with oxidation of excess zinc in the lattice. AbstractZinc oxide films of high optical quality have been deposited onto both silica and silicon substrates using reactive sputtering, pulsed laser deposition, and an aqueous solution based technique. Films have been characterized with respect to crystalline phase and phase stability, surface morphology, and optical response by means of Xray diffraction, Raman Spectroscopy, Atomic Force Microscopy, optical transmission and ellipsometry measurements. All. films studied were of the wurtzite phase, finegrained, and exhibited varying degrees of c-axis orientation with respect to the substrate normal depending upon deposition conditions. Films showed some degree of residual tensile stress which was inferred from the E2 Raman line shift relative to the single crystal frequency. The wurtzite phase was found to be stable to temperatures near 800°C, but at higher temperatures, reaction with silica led to evolution of Zn2Si04 at the interface. Variations in Raman fine intensities upon post deposition annealing has been correlated with oxidation of excess zinc in the lattice.