Collection and in situ analyses of regolith samples by the Mars 2020 rover: Implications for their formation and alteration history

The Perseverance rover has sampled mm-size lithic fragments containing olivine likely from at least two source regions from the surface of an inactive megaripple surface, and fine-grained material from the surface and to a depth of ~ 4-6 cm. Some of the mm-size grains lack a coherent diffraction pattern measured by PIXL, consistent with the presence of poorly-ordered secondary phases . Analysis of these materials on Earth will allow examination of evidence of ancient aqueously altered environments that could have been habitable, and, if Mars contained life, possibly biosignature-containing. Fluorescence of three different patterns was detected, which are consistent with inorganic emissions from silica defects or Rare Earth Elements in certain mineral phases, though organic origin cannot be excluded. Analysis of ACI and WATSON images of the subsurface material and MEDA thermal inertia measurements indicate grain sizes of ~125 µm and ~150 μm, respectively, for the bulk material within the megaripple.Examination of the fine-grained material in the sampling location indicates chemical compositions similar to previously proposed global components as well as the presence of airfall dust. In situ and associated atmospheric measurements also provide evidence of recent atmospheric processes likely including water vapor in the formation of soil crusts. This sample will help elucidate the formation processes of martian soils as well as allow the study of current surface-atmosphere interactions. The composition, shape, and size distribution of dust grains is valuable for studies of past and present martian climate (in which dust radiative and microphysical effects are important) and for assessing potential health and other risks to human missions.