Compositional Variations in Sedimentary Deposits in Gale Crater as
Observed by ChemCam Passive and Active Spectra
Abstract
During the first 2934 sols of the Curiosity rover’s mission 33,468
passive visible/near-infrared reflectance spectra were taken of the
surface by the mast-mounted 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 (PCA) and various spectral parameters including the
band depth at 535 nm and the slope between 840 nm and 750 nm. Four
endmember 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 near-infrared (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 towards
steeper near-infrared slope is seen in the Hutton interval, indicative
of changing depositional conditions or increased diagenesis.