LEAVING GLEN TORRIDON: BEDROCK GEOCHEMISTRY MEASURED BY CHEMCAM EN ROUTE TO THE SULFATE UNIT OF GALE CRATER
Résumé
Since January 2019, the Mars Science Laboratory (MSL) rover Curiosity has been exploring the Glen Torridon (GT) region of Gale crater, which corresponds to the topographic trough between the Vera Rubin ridge and the Greenheugh pediment (Fig. 1). From orbit, this region stands out due to the rela-tively strong near-infrared signatures of clay minerals [1,2]. The data collected on the ground by Curiosity 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 and sedimentological settings [5].
In particular, the bedrock chemistry measured by ChemCam shows elevated values of the Chemical Index of Alteration (CIA) throughout most of Glen Torridon [6,7], which indicates an open-system type of alteration [8]. In addition, the ChemCam observations suggest the presence of illite in the fine-grained rocks [9] and reveal a possible relationship between grain size and geochemical variations [10]. Finally, they show that the light-toned rocks located just below the uncon-formity at the base of the Greenheugh pediment (and drilled at Hutton; Fig. 1) are associated with “anoma-lous” bedrock compositions that may be related to a late-stage diagenetic event at Gale [7].
Here, we report the findings of the ChemCam instrument during the last stretch of the GT campaign, from Bloodstone Hill to the Sands of Forvie (Fig. 1). At the conference, we will also present the data acquired in early 2021, as Curiosity approaches the transition into the sulfate-bearing unit.
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