Europa's ice-related atmosphere: The sputter contribution

Our results match available observational data and previously published modeling efforts well. Europa's exosphere is dominated by thermally accommodated O2 close to the surface (below a few 100 km), and the much lighter H2 molecules at higher altitudes. The water-ice related species that stick to the surface (freeze out) are liberated by cold and hot plasma sputtering in about equal amounts. In addition, in the case of H2, O2, and H2O2, electrons contribute almost as significantly to the sputter yield as ions do.