E.L. Moreland1, R.E. Arvidson2, 3, R.V. Morris4, T. Condus2, 3, M.N. Hughes2, 3, C.M. Weitz5, and S.J. VanBommel2, 3
1Department of Earth, Environmental, and Planetary Sciences, Rice University, Houston, TX.
2Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, MO.
3McDonnell Center for the Space Sciences, Washington University in St. Louis, St. Louis, MO.
4ARES, NASA Johnson Space Center, Houston, TX.
5Planetary Science Institute, Tucson, AZ.
Draft for Journal of Geophysical Research: Planets
06/21/22
Corresponding author: Eleanor Moreland (morelandellie@rice.edu)
Key Points:
Abstract
The Bagnold linear dune field investigated by Curiosity at Mount Desert Island (MDI) is in Gale crater, north of the ~5.5 km high Aeolis Mons mound. False-color images (RGB, 2.496, 1.802, and 1.235 µm, respectively) generated from Mars Reconnaissance Orbiter (MRO) Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) data show the dune field has a reddish-brown color. A sand sheet located south of the Bagnold dunes, the Sands of Forvie (SoF), is darker and lacks the reddish-brown color. Single scattering albedo (SSA) spectra retrieved at 12 m/pixel using along‑track oversampled CRISM observation FRT00021C92 show a long wavelength (1.7 to 2.5 µm) rise for the MDI dunes. Over the same wavelength interval, SoF is characterized by a broad ~2.2 µm absorption feature, consistent with color differences between the two deposits. Checkerboard unmixing of the SSA image cube isolated spectral endmembers within the MDI and SoF. Nonlinear modeling using Hapke (2012) theory implies finer grain sizes for MDI compared to SoF, with inferred abundances of basaltic glass > feldspar > olivine > pigeonite > augite for MDI, and basaltic glass > feldspar > augite > olivine for SoF. These results are similar for the mean spectra of each region and coincide with Curiosity ‑based observations that MDI contains smaller ripples with overall finer grains, while SoF has large megaripples and concentrated coarser grains on the crests. Although these deposits are only located ~2.5 kilometers away from one another, wind and local topographic controls influence their grain size and mineralogy.
Plain Language Summary
In Gale Crater, both the Mount Desert Island (MDI) area within the Bagnold dune field and the Sands of Forvie (SoF) deposit located to the south of Glen Torridon have been shown, using Curiosity rover data, to consist of basaltic materials. We employed along-track oversampled CRISM hyperspectral image data (0.50 to 2.6 µm) covering these areas and processed images to retrieve surface spectra free of the influence of atmospheric aerosols and gases. Non-linear modeling of the spectra on a pixel-by-pixel basis shows that spectral differences between the two sand sheets are a consequence of differences in glass and pigeonite contents, together with coarser grains in the Sands of Forvie deposit. Results are consistent with wind-induced preferential migration of finer grains up onto the Greenheugh pediment for SoF, as opposed to the uninhibited downwind migration of the MDI sands. Results are also relevant to understanding wind-blown sand deposits in the Martian rock record, considering that the two sand deposits are located only ~2.5 kilometers from one another, yet have different characteristics that are a consequence of local topographic controls.
1 Introduction
The Mars Science Laboratory (MSL) rover Curiosity has explored the northwestern floor of Gale crater and its central ~5.5 km tall mound, Aeolis Mons (informally named Mount Sharp), focusing on investigating exposed strata to infer past environments of deposition and overall potential for ancient habitability (Grotzinger et al., 2012, 2015; Vasavada et al., 2014; Bennett et al., 2022; and references therein). The local radiation environment, atmospheric dynamics, and the nature of modern sand deposits have also been investigated (e.g., Vasavada et al., 2014 and references therein). Sand measurements using Curiosity ’s instrument payload have been conducted at multiple locations, largely focusing on the Bagnold dune field to the north of Mount Sharp (e.g., Bridges & Ehlmann et al., 2018; Lapotre & Rampe, 2018; Figure 1). In-situ data from the sands have also been used synergistically with Mars Reconnaissance Orbiter (MRO) Compact Imaging Spectrometer for Mars (CRISM; Murchie et al., 2007) observations to extend interpretations of the nature of the dunes from the relatively small areas characterized by the rover to larger regions covered by hyperspectral imaging data (e.g., Lapotre et al., 2017a; Rampe et al., 2018). Within the Bagnold dune field, observations at the Namib barchan dune and at the Nathan Bridges and Mount Desert Island (MDI) linear dune deposits were made (Lapotre & Rampe, 2018). On Mt. Sharp, Curiosity -based measurements were acquired at the northern edge of the Sands of Forvie (SoF) sand sheet located on the southern edge of Glen Torridon (Weitz et al., 2022; Sullivan et al., 2022; Figure 1). In this paper we extend the synergistic and comparative analyses of Curiosity and CRISM-based data sets to include Curiosity ’s southern Bagnold dune measurements (MDI area) and the SoF sand sheet. We utilize CRISM along-track oversampled observation (ATO) FRT00021C92 which covers both sites to add orbital perspectives to the analyses.