Using ChemCam LIBS data to constrain grain size in rocks on Mars: Proof of concept and application to rocks at Yellowknife Bay and Pahrump Hills, Gale crater

Abstract

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Grain Size Variations in the Murray Formation: Stratigraphic Evidence for Changing Depositional Environments in Gale Crater, Mars

“…The first evidence of a return to fluvial facies is marked by cross-stratified GSR4 rocks at Newport Ledge and Heron Island (Figure 7). The coarse grain sizes and trough cross stratification in this area are similar to those at the Shaler outcrop of the Yellowknife Bay formation (Anderson et al, 2015;Edgar et al, 2017;Grotzinger et al, 2014;Rivera-Hernández et al, 2019). The Shaler depositional environment was constrained by detailed image-based analyses of grain size, sorting, shape, and bed-set geometries, leading to a fluvial interpretation (Edgar et al, 2017), with GIMS analyses demonstrating the dominance of GSR3-GSR4 targets (Rivera-Hernández et al, 2019).…”

“…Here, we apply the GIMS technique to the abundance of ChemCam LIBS data to help characterize the sedimentary facies of the Murray formation. Results from this study add to grain size information acquired using image data Stack et al, 2019;Rivera-Hernández et al, 2019). These refined grain size constraints provide new insights into the details of the depositional environments preserved in the Murray formation and thus enhance our understanding of the habitability of early Mars.…”

A Lacustrine Paleoenvironment Recorded at Vera RubinRidge, Gale Crater: Overview of the Sedimentology and Stratigraphy Observed by the Mars ScienceLaboratory Curiosity Rover

“…The facies associations and observed southward transport direction predicted that the rover would eventually encounter deposits from a body of standing water. This was confirmed when the rover drove into Hidden Valley and the Pahrump Hills and the team discovered a thick succession of fine‐grained, well laminated rocks, interpreted to have formed through lacustrine deposition (Grotzinger et al, ; Rivera‐Hernández et al, ; Stack et al, ). Evidence for plunging river plumes at the Pahrump Hills favors a freshwater lacustrine origin based on paleohydraulic modeling (Stack et al, ).…”

Studies of a Lacustrine‐Volcanic Mars Analog Field Site With Mars‐2020‐Like Instruments

“…With both instruments, bulk chemistry can always be observed by multipoint averaging, yielding data similar to APXS measurements familiar from past rover missions (Gellert et al, 2013;Golombek, 1997;Rieder et al, 2003). Additionally, a method has been developed for estimating relative grain size from the compositional spread of the observation points within a ChemCam raster (Rivera-Hernández et al, 2018). At large grain size, individual grains will dominate the chemistry as measured at one point, thus increasing the variability between points, while a grain size much smaller than the laser spot size will yield more consistent chemistry between points (Rivera-Hernández et al, 2018).…”

“…Additionally, a method has been developed for estimating relative grain size from the compositional spread of the observation points within a ChemCam raster (Rivera-Hernández et al, 2018). At large grain size, individual grains will dominate the chemistry as measured at one point, thus increasing the variability between points, while a grain size much smaller than the laser spot size will yield more consistent chemistry between points (Rivera-Hernández et al, 2018). This technique requires that samples with large grain size exhibit chemical variability and that diagenetic cements do not dominate at large grain size, as cement may cause the sample's chemistry to appear more homogenous than its true bulk chemistry.…”