Exploration of subsurface structure in eastern Coprates and Capri Chasmata, Mars using radar sounding data

Abstract:

Valles Marineris, the largest stratigraphic exposure on Mars, has been characterized by ancient water‐related geologic features (e.g., a variety of aqueous minerals and fluvial topography) and abundant recurring slope lineae (RSLs). We surveyed the subsurface structure in eastern Coprates and Capri Chasmata, the eastern portion of Valles Marineris, using high‐resolution visible images, digital terrain models, and radar sounding data. We identified subsurface reflectors in four areas of the chasmata. At the stratigraphic exposure on the chasmata walls, the plausible corresponding depth of the reflector is ∼60 m. The bulk dielectric constants of the layers above the reflectors are calculated as 3.4–4.0. This bulk dielectric constant constrains the bulk porosity: 39.3 ∼ 46.1% and the upper limit of the water ice fraction: ∼7.8 and 21.2% of layers above a Hesperian lava. This high bulk porosity can be explained by emplacements of aeolian, fluvial, and/or porous volcanic materials in the Hesperian. In any case, evidence of repetitive drastic geological changes of the Hesperian environment and/or volcanic activity, which produce alternating layers of lower and higher porosity layers, is exposed on the chasmata wall. Considering the current instability of water ice in low‐latitude terrain, if water-ice actually exists, further studies and discussions are required on the mechanism necessary to maintain it within this region.