Bedrock geochemistry measured by ChemCam along a 2-km eastward traverse in the Glen Torridon region, Gale crater, Mars

International audience ; In January 2019, the Mars Science Laboratory (MSL) rover Curiosity started exploring the GlenTorridon (GT) region of Gale crater, which corresponds to the topographic trough between the VeraRubin ridge and the Greenheugh pediment (Fig. 1). From orbit, this region stands out due to therelatively strong near-infrared signatures of clay minerals [1,2]. The in-situ data collected so far byCuriosity have allowed the MSL team to confirm and quantify the presence of these clay minerals[3], to characterize their organic content [4], and to document in detail their geochemical andsedimentological settings [5].In particular, the bedrock chemistry measured by ChemCam shows elevated values of the ChemicalIndex of Alteration (CIA) throughout most of Glen Torridon [6,7], which indicates an open-systemtype of alteration [8]. In addition, the ChemCam observations suggest the presence of illite in thefine-grained rocks [9] and reveal a possible relationship between grain size and geochemicalvariations [10]. Finally, they show that the light-toned rocks located just below the unconformity atthe base of the Greenheugh pediment (Fig. 1) are associated with “anomalous” bedrockcompositions that may be related to a late-stage diagenetic event at Gale [7].Here, we report the findings of the ChemCam instrument along a ~2-km eastward traverse withinthe upper member – named Glasgow – of the Glen Torridon region (Fig. 1). This traverse allowedCuriosity to investigate the lateral variability of this member, while also getting gradually closer tothe transition into the overlying sulfate-bearing unit [11].DatasetChemCam measures the chemical composition of targeted rocks and soils within a few meters of therover using laser-induced breakdown spectroscopy (LIBS). Quantification of eight major rockformingoxides is performed routinely [12]. Each ChemCam analysis consists of a raster of severalpoints a few millimeters apart from each other, and each point itself consists of a series of lasershots (typically 30). For ...