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:
- Orbital and in-situ data show variation between the basaltic sands
that dominate the active Bagnold dunes and Sands of Forvie sand sheet.
- The two deposits are separated by ~2.5 kilometers, so
this variation is relevant to interpretation of aeolian transport
processes on Mars.
- The variation is interpreted to result from unconstrained dune
migration versus topographically inhibited migration for the sand
sheet.
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.