Geologic context of the bright MARSIS reflectors in Ultimi Scopuli, South Polar Layered Deposits, Mars

TL;DR

This study uses high-resolution imaging and radar data to analyze the geologic context of bright reflectors beneath Mars' South Polar Layered Deposits, challenging the hypothesis of subglacial lakes.

Contribution

It provides a detailed geologic mapping that refutes the presence of surface modifications associated with proposed subglacial lakes.

Findings

No evidence of surface features linked to subglacial lakes

Identification of multiple geologic units with CO2 and aeolian features

Contradicts the interpretation of bright reflectors as subglacial lakes

Abstract

Radar-bright basal reflectors have been detected below the South Polar Layered Deposits (SPLD), Mars using Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) data and have an exciting but controversial interpretation: liquid water from subglacial lakes. We mapped the surface of the SPLD immediately above and surrounding the putative lakes (1:2M map scale) in order to provide geologic context for interpretation of the bright basal reflectors. We use THEMIS daytime IR (100 m/pixel), CTX (6 m/pixel), and HiRISE (25 cm/pixel) data to characterize geologic units and typical surface roughness. We find evidence for multiple geologic units with features due to CO2 and aeolian-related processes. We do not find evidence for surface modification linked to the postulated lake locations. This is not consistent with the interpretation of the MARSIS basal radar reflector as subglacial lakes.