Saponite Bearing Material Excavated During the Formation of a Recent 25‐m‐Diameter Impact Crater in Southeastern Arabia Terra on Mars

Abstract Mars Reconnaissance Orbiter's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), Context Imager (CTX), and High Resolution Imaging Science Experiment observations were analyzed for a 25‐m‐wide impact crater and associated ejecta deposits located in the dust‐covered Arabia Terra region. The crater formed within plains nestled inside the degraded rim of a Noachian‐aged crater. Temporal image coverage constrains the impact event to between the years 2010–2012. The crater morphology and proximal and far‐ranging ejecta deposits, together with lunar analogs and impact simulations, collectively indicate a hypervelocity impact from an incoming heliocentric bolide. A CRISM along‐track oversampled observation (0.45–3.75 μm) covering the crater and its ejecta deposits was processed to retrieve surface single‐scattering albedos and surface temperatures, followed by regularization of overlapping 18‐m‐wide pixels to a projected spatial resolution of 12 m/pixel. Spatial variations in mapped temperatures show that ejecta emplacement altered the surface thermophysical properties relative to the undisturbed dusty terrain. Results show that the proximal ejecta deposit, excavated from only a few meters in depth, includes magnesium saponite with more Fe 2+ than Fe 3+ in the octahedral sheet. This discovery provides a rare view into the subsurface of a dusty area and indicates that aqueous alteration is more widespread than previously inferred from surface exposures amenable to mapping via orbital spectroscopy. It is also consistent with saponite formation in an anoxic environment without complete oxidation.