Chemical mapping of Martian meteorite SaU-008 using deep UV Raman and Fluorescence Spectroscopy on Earth and Mars

NASA’s Perseverance Mars rover carries a piece of Martian meteorite Sayh al Uhaymir (SaU) 008 as part of the calibration payload for the SHERLOC science instrument. We report SHERLOC observations of the SaU-008 flight piece over the first 1000 sols of the mission and compare them to measurements done prior to launch, showing consistent detection of the same deep-ultraviolet (DUV) Raman and fluorescence signatures in the same locations. Co-located X-ray fluorescence (XRF) and DUV mapping of a reference SaU-008 piece on Earth confirm that the meteorite is comprised of an igneous mineral matrix consistent with shergottite, rich in olivine, maskelynite, and Fe-Mg pyroxenes detectable by SHERLOC. Terrestrial weathering features consist of fractures and vugs filled with Ca-carbonate. Fluorescence mapping reveals two major signatures: 1) a broad-spectrum fluorescence present throughout the igneous matrix but strongest in weathering features, attributed to organic material, and 2) a narrow-band 340 nm fluorescence spatially associated with ~48 ppm Ce in <100 μm Ca-phosphate grains. Raman reveals organic material in both the igneous matrix and terrestrial carbonate in the form of macromolecular carbon (MMC) with defective and graphitic bands at ~1380 and ~1600 cm−1. Raman band parameters suggest that MMC associated with terrestrial weathering is less thermally mature, most likely the result of chemical alteration after landing on Earth. This study serves as a demonstration of SHERLOC’s capabilities when supported by co-located XRF data from PIXL, and suggests SHERLOC may be able to detect Ce in phosphate minerals at concentrations as low as 4 ppm.