Compositional Variations in Sedimentary Deposits in Gale Crater as Observed by ChemCam Passive and Active Spectra

During the first 2934 sols of the Curiosity rover's mission 33,468 passive visible/near-infrared (NIR) reflectance spectra were taken of the surface by the mast-mounted Chemistry and Camera (ChemCam) instrument on a range of target types. ChemCam spectra of bedrock targets from the Murray and Carolyn Shoemaker formations on Mt. Sharp were investigated using principal component analysis and various spectral parameters including the band depth at 535 nm and the slope between 840 and 750 nm. Four end-member spectra were identified. Passive spectra were compared to Laser Induced Breakdown Spectroscopy (LIBS) data to search for correlations between spectral properties and elemental abundances. The correlation coefficient between FeOT reported by LIBS and BD535 from passive spectra was used to search for regions where iron may have been added to the bedrock through oxidation of ferrous-bearing fluids but no correlations were found. Rocks in the Blunts Point-Sutton Island transition that have unique spectral properties compared to surrounding rocks, that is flat NIR slopes and weak 535 nm absorptions, are associated with higher Mn and Mg in the LIBS spectra of bedrock. Additionally, calcium-sulfate cements, previously identified by Ca and S enrichments in the LIBS spectra of bedrock, were also shown to be associated with spectral trends seen in Blunts Point. A shift toward a steeper NIR slope is seen in the Hutton interval, indicative of changing depositional conditions or increased diagenesis.

Automated summary

During the first 2934 sols of the Curiosity rover's mission, the ChemCam instrument on the rover collected 33,468 passive visible/near-infrared reflectance spectra of various types of bedrock on Mount Sharp. The spectra were analyzed using principal component analysis and various spectral parameters, leading to the identification of four different end-member spectra. Correlations between spectral properties and elemental abundances were investigated, and associations between unique spectral properties and higher Mn and Mg concentrations in the bedrock were found. The presence of calcium-sulfate cements and a shift in the NIR slope in the Hutton interval were also observed.