PacMan returns: An electron-generated thermal anomaly on Tethys

Abstract

New Cassini observations show that Saturn’s moon Tethys, like Mimas, has a region of anomalously high thermal inertia at low latitudes centered on its leading hemisphere. Derivation of the thermophysical properties of the surface across three representative regions indicate that the bolometric Bond albedo across Tethys’ leading hemisphere remains constant, within error, whilst the thermal inertia increases from 5±1Js−1m−1K−1 outside of the anomalous region to 25±3Js−1m−1K−1 inside. The thermally anomalous region is spatially correlated with a decrease in the IR/UV surface coloration. The discovery greatly strengthens the hypothesis that high-energy electrons, which preferentially bombard the leading hemispheres on both satellites, produce dramatic alterations in surface texture.