Quantifying lava surface heterogeneity on Mars using THEMIS brightness temperature data

Abstract

The analysis and characterization of any planetary surface relies heavily on orbital data. The Martian surface is dominated by extrusive volcanism with most of the younger rocks being either too rough or at altitudes that are commonly inaccessible to landers or rovers. Therefore, the accurate interpretation of orbital data is critical to understanding the planet's youngest magmatic conditions and subsequent cratering and eolian history. However, the cumulative effects of surface processes such as dust deposition spanning millions of years typically obscures observable features, posing challenges for data analysis. This study focuses on the igneous terrains from Arsia Mons and into Daedalia Planum using a unique off-nadir thermal infrared (TIR) dataset acquired through special tasking of the Mars Odyssey spacecraft. Prior studies of this region indicated compositional variations were present, yet the dust cover made conclusive results impossible. This study introduces a novel methodology that combines the KRC thermal model, quantitative thermal inertia data, and the off-axis TIR observations to predict surface temperature and quantify submeter-scale surface roughness. In doing so, we reveal changes in lava flow roughness that can be correlated to relative flow ages, flow dynamics, and preferential mantling of dust. These data are compared to older, nadir pointing, THEMIS emissivity data to quantify the anisothermality caused by surface roughness. The results underscore the significance of existing orbital data acquired and processed in novel ways to retrieve new information about Martian volcanology and the ongoing dynamics acting on these surfaces.