THEMIS‐VIS Investigations of Sand at Gale Crater

Abstract

Gale crater is the landing site of the Mars Science Laboratory (MSL) rover, Curiosity. Here we present Thermal Emission Imaging System Visible Imaging Subsystem (THEMIS‐VIS) mosaics in gray scale and in false color of Gale crater. We use these data products, in addition to THEMIS thermal infrared decorrelation stretch (DCS) mosaics, thermal inertia derivations, and near‐infrared spectra to investigate the MSL traverse area and sand across Gale crater. We identified several THEMIS‐VIS color units in the MSL traverse area that may correlate to the amount of sand cover that is present on each unit. This suggests that THEMIS‐VIS color is extremely useful in identifying dark basaltic sand, which appears as blue in THEMIS‐VIS false color images. We test this hypothesis by identifying small (~several pixels) blue patches on the southeast side of the central mound in Gale crater and confirming that they are patches of sand in High Resolution Imaging Science Experiment (HiRISE) images. Sand dunes on the crater floor exhibit variations in all data sets utilized in this study, with the Bagnold dunes and the western sand sea exhibiting the most notable differences. We propose that these differences are the result of a thin layer of dust that covers the western sand sea, although we do not rule out possible effects from grain size sorting.

Gardening of the Martian Regolith by Diurnal CO2 Frost and the Formation of Slope Streaks

“…The THEMIS visible camera has a resolution of 18 m/pixel and has five filters with band centers located at 425 (band 1), 540 (band 2), 654 (band 3), 749 (band 4), and 860 nm (band 5; P. R. Christensen et al., 2004). When available, we used “R2B” images, a colorized product where of band 4 (red) and band 1 (blue) are combined using 0.65 × band 1 + 0.35 × band 4 to generate a simulated green band used for the RGB composite (Bennett et al., 2018; Murray et al., 2016). When not available, we used conventional RGB composite resulting from band 4 (or, if not available, band 3), band 2, and band 1 in the blue channel (Bennett et al., 2018; Murray et al., 2016).…”

“…When available, we used “R2B” images, a colorized product where of band 4 (red) and band 1 (blue) are combined using 0.65 × band 1 + 0.35 × band 4 to generate a simulated green band used for the RGB composite (Bennett et al., 2018; Murray et al., 2016). When not available, we used conventional RGB composite resulting from band 4 (or, if not available, band 3), band 2, and band 1 in the blue channel (Bennett et al., 2018; Murray et al., 2016). Surface frosts are identified based on their blue/white hues, in stark contrast with the orange/brown/gray surrounding terrains, in spite of the challenging illumination conditions (Figure 3).…”

Surface Kinetic Temperatures and Nontronite Single Scattering Albedo Spectra From Mars Reconnaissance Orbiter CRISM Hyperspectral Imaging Data Over Glen Torridon, Gale Crater, Mars

“…Wind-blown sand deposits within Gale Crater range from the extensive barchanoid and longitudinal Bagnold Dunes (e.g., Ehlmann et al, 2017; Figures 1 and 2) to ripple-dominated sand sheets such as the Sands of Forvie (Figure 3). Bennett et al (2018) used Odyssey'sThermal Emission Spectrometer Image System multispectral data, HiRISE, and CRISM data (<2.4 μm) to evaluate sand compositions across Gale Crater's floor. Our analyses focus on Sands of Forvie at high spatial resolution (12 m/pixel), cover the full CRISM spectral range with full atmospheric corrections, incorporates HiRISE data, and uses Curiosity data for synergistic comparisons to the orbiter data.…”

Diagenesis Revealed by Fine‐Scale Features at Vera Rubin Ridge, Gale Crater, Mars

“…Sharp shows stratigraphic changes in mineralogy, observable from orbit, that are inferred to record a transition from more water-rich environments conducive to clay-mineral formation to more water-poor environments conducive to the precipitation of evaporative sulfate minerals (Milliken et al, 2010;Thomson et al, 2011 (Smith et al, 2001), with a black star showing the location of Gale crater. (b) Thermal Emission Imaging System Visible Imaging Subsystem (THEMIS-VIS) grayscale mosaic of Gale crater (Bennett et al, 2018), showing the region of exploration along the NW margin of Mt. Sharp.…”

“… (a) Global Mars Orbiter Laser Altimeter (MOLA) elevation map of Mars (Smith et al., 2001), with a black star showing the location of Gale crater. (b) Thermal Emission Imaging System Visible Imaging Subsystem (THEMIS‐VIS) grayscale mosaic of Gale crater (Bennett et al., 2018), showing the region of exploration along the NW margin of Mt. Sharp.…”