A Global Plume-Fed Europan Exosphere: Structure, Composition, Temporal Variability, and Surface Interactions

Abstract:

We present results from our Europa global exospheric modeling, which includes both sputtering / radiolytic and potential plume sources, and a sophisticated treatment of the exosphere-surface interaction, i.e., surface adsorption, regolith diffusion, polar cold trapping, and re-sputtering of adsorbed materials. We consider the effect of Europa’s gravity in pulling plume vapor back to the surface and the subsequent spreading of adsorbed and exospheric material by thermal desorption and re-sputtering across the entire body. Our results show the global spatial distribution and temporal evolution of the surface exospheric density and composition for several scenarios, e.g., a solely sputtered / radiolytic exosphere, and the inclusion of transient and/or steady plume sources with an Enceladus-like composition. The model provides a useful tool for interpreting remote observations, and for extrapolating possible neutral and ion densities and compositional profiles along potential future spacecraft trajectories.