Radar-derived Compositional Diversity of the Youngest Martian Volcanics: An Exploratory Study

Abstract Understanding the compositional diversity of young Martian volcanics is crucial for tracing magmatic processes and the thermal evolution of the planet. Here, we build on previous orbital radar-based dielectric analyses of lava flows by applying the SHAllow RADar split-chirp technique, which decomposes the radar signal into multiple bands to estimate bulk loss tangent (tan δ ). We apply this method to subsurface detections at nine Amazonian volcanic deposits with thickness greater than about 30 m, spanning a range of ages and regions. By leveraging an empirical framework derived from lunar sample analyses, we investigate the geochemical controls on subsurface radar attenuation. Our results reveal a broad range of loss values, most aligning with plausible oxide and density constraints. These findings highlight the potential for orbital radar loss estimates to distinguish igneous geochemical variations, providing a pathway toward a global-scale compositional mapping strategy for Martian volcanism. To provide context for our volcanic compositional analysis, we also undertook new loss estimates of glacial deposits, revealing significantly lower tan δ values that are consistent with near-pure ice. Cautious use of the split-chirp technique across all viable lava flow deposits could offer insights into Martian compositional diversity and magma evolution over the last three billion years, informing future in situ analyses and sample collection efforts.