Mineralogy of Aeolian Deposits in Gale Crater, Mars: The Bagnold Dunes to Glen Torridon

We select four sand deposits along the traverse of the Curiosity rover to evaluate the spatial distribution of mineralogy and grain size. While extensive work has focused on characterizing the Bagnold Dunes in-situ and from orbit, less attention has been given to deposits south of the Vera Rubin Ridge (VRR). Overall, our results illustrate a compositional dichotomy among aeolian deposits, separated by the VRR. Initial investigations of hyperspectral data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) show differences in the long wavelength spectral features and absolute reflectance measurements for the deposit south of the Bagnold Dunes. The southern deposits show a larger absorption feature at ~2.12 μm while the Bagnold Dunes region has a steeper spectral slope from 2.2-2.5 μm. Performing unmixing analysis of hyperspectral data provides an estimated probability distribution of the abundance and grain size of minerals present in the spectra of these deposits. These data suggest the 2.12 μm feature is a function of pigeonite abundance while the spectral rise is due to amorphous material. Using two of Curiosity’s stops, Mt. Desert Island and the Sands of Forvie, as anchor sites, reflectance measurements suggests a larger grain size in the Sands of Forvie compared to Mt. Desert Island. Mapping the distributions of mineral abundance and grain size, the linear Bagnold Dunes, to the north of the ridge, contain higher abundances of forsterite and amorphous material than those to the south which contain more pigeonite. Grain sizes tend to be higher in the deposits south of the ridge, specifically in regards to the amorphous material and labradorite. These findings suggest the possibility of either different wind regimes acting on different sides of the VRR or different sediment sources for deposits depending on which side of the ridge they occur.