MINERALOGY AND STRATIGRAPHY OF GALE CRATER RIM, WALL, AND FLOOR UNITS
Our analyses show Fe,Mg-phyllosilicates are detected over a significant area of Gale and are a key mineralogical component of the bedrock and crater floor units. The Fe-Mg smectites and hydrated phases observed on the floor of Gale and in the Mt. Sharp sediments may be formed in situ or transported. If transported, the sedimentary smectites should match source material spectral properties. However the wavelength of the metal-OH absorption varies slightly in different outcrops. A key difference in all spectra is the presence of a 2.23-micron absorption characteristic of AlFe-OH in Mt. Sharp sediments that is absent in the wallrock and floor materials. Additionally there is regional variability in the strength of water-related absorptions with some regions displaying only absorptions associated with hydroxylation and not water. These imply that the lower Mt. Sharp phyllosilicate unit and the phyllosilicate-bearing materials found elsewhere in Gale differed in starting protolith and/or the chemistry of altering fluids. We are currently mapping the stratigraphic relationships of the wall, valles, and floor units.
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