Thermal Redistribution and Recrystallization of Ice on Europa's Surface

The bulk of Europa's crust is dominated by water ice. Emplacement of internally derived hydrated salt minerals and production of sulfuric acid hydrates through the action of the jovian magnetosphere result in spatial variations in the non-ice surface composition. Recent observations from the James Webb Space Telescope (JWST) suggested the presence of H₂O ice in both crystalline and amorphous form, with evidence for rapid (~10 day) recrystallization of ice in some regions and the dominance of amorphization via plasma sputtering in others (Cartwright et al., 2025, PSJ). Sublimation and sputtering may also supply water to the exosphere, through which it is transported ballistically to other regions on Europa. Here, we use a 3D thermophysical model with coupled sputtering and exosphere transport models to examine the redistribution of water and its effect on Europa's surface composition.

 

Our results indicate that for a surface with initial non-ice concentrations of a few percent, sublimation dominates ice ablation at the low- to mid-latitudes, with net accumulation at the poles. Sputtering (also a temperature-dependent process) accounts for a few percent of net ice ablation. On diurnal to annual timescales, a prominent spatial pattern of ice concentration develops: 1) depletion of ice (enrichment in non-ice) at the equator relative to both the mid-latitudes and the polar regions, and 2) a longitudinal variation with higher ice concentrations (less ablation) at the subjovian hemisphere. The latter effect is due to the daily solar eclipse of Europa by Jupiter, which suppresses local noontime peak temperatures along with sublimation and sputtering rates. In addition to the thermophysical and ice transport results, we will present rates and spatial patterns of amorphization and thermal recrystallization to better understand the JWST observations.