The chemical composition of the Soi crater region on Titan.

The Soi crater region, with the well-preserved Soi crater in its center, covers almost 10% of Titan’s surface. Schoenfeld et al. (2023) [1] mapped this region at 1:800,000 scale and produced a geomorphological map showing that the area consists of 22 distinct geomorphological units. The region includes the boundaries between the equatorial regions of Titan and the mid-latitudes and extends into the high northern latitudes (above 50o). We analyzed 262 different locations from several Visual and Infrared Mapping Spectrometer (VIMS) datacubes using a radiative transfer technique [2] and a mixing model [3], yielding compositional constraints on Titan’s optical surface layer and near-surface substrate compositional constraints using RADAR microwave emissivity. We have derived combinations of top surface materials between dark materials, tholin-like materials, water-ice, and methane. We found no evidence of CO2 and NH3 ice. We discuss our results in terms of origin and evolution theories.[1] Schoenfeld, A., et al. (2023), JGR-Planets 128, e2022JE007499; [2] Solomonidou, A., et al., (2020a), Icarus, 344, 113338; [3] Solomonidou, A., et al. (2020b), A&A, 641, A16.