Subsurface signatures of bright terrain formation models on Ganymede by 3D radar sounder simulations

Abstract

The Radar for Icy Moon Exploration (RIME) on-board the JUICE mission will look for dielectric and mechanical interfaces below the icy crust of the Galilean moon Ganymede. Previous missions suggest that the surface of Ganymede is covered by two types of terrains, namely the dark terrain and bright terrain. The bright terrain covers two-thirds of the surface, and presents two main morphologies, i.e. the grooved and smooth bright terrains. For understanding the geological history of Ganymede, a still-open question regards the sequence and styles of processes that formed these morphologies. While in the literature different formation hypotheses are highly debated, direct evidence of these can be proven by subsurface probing, for which RIME will offer a unique opportunity. In this work, we aim to understand whether RIME can actually detect and differentiate between the different hypotheses. To this purpose, we perform 3D simulations of RIME radargrams, following a progressive insertion approach which allows to simplify the data interpretability. We focus on the bright terrain morphologies and analyze in detail the RIME detectability of geological components that can support the formation hypotheses of the grooved and smooth bright terrains. The results suggest that RIME can possibly detect the subsurface interfaces associated with the geological components, and differentiate between their radar responses. We also provide a key to interpretation of the RIME data over these targets, and link the radar responses to the formation hypotheses debated in the literature.