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

Abstract

The Mars Reconnaissance Orbiter Compact Imaging Spectrometer for Mars (CRISM) covers the spectral range from 0.362 to 3.92 μm with a midafternoon local solar time data acquisition. For equatorial to midlatitudes, depending on the season and surface materials, wavelengths longer than ∼2.65 μm exhibit spectral radiances on sensor that include sunlight and thermal‐emission related terms. We developed a radiative transfer based neural network approach to model both solar and emitted terms in which surface kinetic temperatures are retrieved for each image pixel, together with single scattering albedo spectra, over the full CRISM wavelength range. We applied the method to along‐track oversampled scene FRT00021C92 over Glen Torridon within Gale Crater, where the Curiosity rover traversed and acquired remote sensing and in‐situ data. Synergistic analysis of orbital and rover‐based data, coupled with laboratory analyses of ferric‐rich smectites, provide a self‐consistent set of results for the presence of desiccated nontronite associated with Murray formation mudstones exposed as periodic bedrock ridges located just to the south of Vera Rubin ridge. The desiccated nature is consistent with Curiosity's CheMin data, which for Glen Torridon drill samples indicate an abundance of nontronite having a collapsed structure resulting from loss of interlayer H2O.

CRISM‐Based High Spatial Resolution Thermal Inertia Mapping Along Curiosity's Traverses in Gale Crater

“…Surface kinetic temperature retrieval was accomplished via a combination of radiative transfer modeling at a series of fixed surface temperatures to estimate the corresponding albedo, and a neural network-based approach to optimize the choice of retrieved surface temperatures based on the overall spectral shape. These methods are similar to those presented in Kreisch et al (2017) and He et al (2022).…”

“…As discussed in He et al. (2022), a larger value in the I/F spectrum at 3.7 μm as compared to 2.5 μm indicates that a strong enough thermal signal has been detected for a reliable temperature retrieval.…”

“…Second, the presence of a detectable thermal emission signal within each pixel was checked by comparing the CRISM I/F values at 2.5 and 3.7 μm. As discussed in He et al (2022), a larger value in the I/F spectrum at 3.7 μm as compared to 2.5 μm indicates that a strong enough thermal signal has been detected for a reliable temperature retrieval. ATI retrieval errors were estimated by adding or subtracting the expected temperature error of 2.9 K to the retrieved CRISM temperature, then inverting with the THM model to calculate a set of upper and lower bounds (Figures 3b and 3c).…”

“…(2019) to denoise and regularize the CRISM observation to 12 m per pixel, along with the methodology developed by He et al. (2022) to separate solar and thermal radiative terms. From these retrieved radiative terms, we then retrieve bolometric Bond albedo (referred to as “albedo” throughout this paper) and surface kinetic temperature on a pixel‐by‐pixel basis from the CRISM observation, which are then used to estimate thermal inertia at 12 m per pixel.…”

“…In particular, we focus on an oversampled CRISM observation covering regions traversed by the Mars Science Laboratory Curiosity rover (Figure 1; Grotzinger et al, 2012). We employ the methodology developed by Kreisch et al (2017) and He et al (2019) to denoise and regularize the CRISM observation to 12 m per pixel, along with the methodology developed by He et al (2022) to separate solar and thermal radiative terms. From these retrieved radiative terms, we then retrieve bolometric Bond albedo (referred to as "albedo" throughout this paper) and surface kinetic temperature on a pixel-by-pixel basis from the CRISM observation, which are then used to estimate thermal inertia at 12 m per pixel.…”