Spectral diversity of rocks and soils in Mastcam observations along the
Curiosity rover's traverse in Gale crater, Mars
Abstract
The Mars Science Laboratory (MSL) Curiosity rover has explored over 400
meters of vertical stratigraphy within Gale crater to date. These
fluvio-deltaic, lacustrine, and aeolian strata have been well-documented
by Curiosity’s in-situ and remote science instruments, including the
Mast Camera (Mastcam) pair of multispectral imagers. Mastcam visible to
near-infrared (VNIR) spectra can broadly distinguish between iron phases
and oxidation states, and in combination with chemical data from other
instruments, Mastcam spectra can help constrain mineralogy, depositional
origin, and diagenesis. However, no traverse-scale analysis of Mastcam
multispectral data has yet been performed. We compiled a database of
Mastcam spectra from >600 multispectral observations and 1
quantified spectral variations across Curiosity’s traverse through Vera
Rubin ridge (sols 0-2302). From principal component analysis and an
examination of spectral parameters, we identified 9 rock spectral
classes and 5 soil spectral classes. Rock classes are dominated by
spectral differences attributed to hematite and other oxides (due to
variations in grain size, composition, and abundance) and are mostly
confined to specific stratigraphic members. Soil classes fall along a
mixing line between soil spectra dominated by fine-grained Fe-oxides and
those dominated by olivine-bearing sands. By comparing trends in soil
vs. rock spectra, we find that locally derived sediments are not
significantly contributing to the spectra of soils. Rather, varying
contributions of dark, mafic sands from the active Bagnold Dune field is
the primary spectral characteristic of soils. These spectral classes and
their trends with stratigraphy provide a basis for comparison in
Curiosity’s ongoing exploration of Gale crater.