Classification of ChemCam LIBS targets from Glen Torridon, Gale crater, Mars

Point-by-point classification of all ChemCam LIBS targets in the Glen Torridon region (sols 2301 to 3007). The targets from the Greenheugh pediment are included for completeness, even though they are not studied in detail here (see Bedford et al., this issue). Columns 5 to 9 contain the geographic and stratigraphic locations of the targets. Columns 10 to 12 contain descriptions of the material that was sampled by the laser at each point, based on visual inspection of rover imagery. Column 13 indicates the quality of the data with respect to focus, based on the examination of the focus curves returned by the instrument each time an autofocus is performed (Peret et al., 2016): “poor” corresponds to a flat or noisy curve; “suboptimal” corresponds to a curve with a maximum at the edge of the range of distances scanned by the autofocus; and “uncertain” corresponds to points for which no focus curve is available, but that are likely out-of-focus given the local target topography visible in the RMI images of the target. Column 14 contains the spacecraft clock, which is unique to each row and enables identification and download of the associated spectra from the Planetary Data System (http://pds-geosciences.wustl.edu/missions/msl/). Columns 15 to 42 contain the major-element oxide composition of each point, except for targets with poor focus or very high FeOT (e.g., iron meteorites), or located beyond 6 meters. Abundances are in wt%. The RMSEP (root mean squared error of prediction) reflects the model accuracy as detailed in Clegg et al. (2017). The “shots stdev” reflects the standard deviation across the laser shots (excluding the first 5). Columns 45 to 49 contain the corrected abundances for SiO2, Al2O3, Na2O and K2O, as well as the corrected sum of oxides, for targets beyond 3.5 m (Wiens et al., 2021). Column 50 contains the calculated value of the Chemical Index of Alteration. Abbreviations used: BH = Bloodstone hill; CB = Central butte; CBU = clay-bearing unit; LT = lateral traverse; MA = Mary Anning; TB = Tower butte; WB = Western butte.