what is the speciality of it's atmosphere?
The surface-bounded atmosphere forms through radiolysis, the dissociation of molecules through radiation. Solar ultraviolet radiation and charged particles from the Jovian magnetospheric environment collide with Europa's icy surface, splitting water into oxygen and hydrogen constituents.
Europa (moon)
 The surface-bounded atmosphere forms through radiolysis, the dissociation of molecules through radiation. Solar ultraviolet radiation and charged particles (ions and electrons) from the Jovian magnetospheric environment collide with Europa's icy surface, splitting water into oxygen and hydrogen constituents.
which of jupiter's moons has water ice surface Europa who discovered it? Galileo Galilei was he the one who named it? The naming scheme was suggested by Simon Marius, who attributed the proposal to Johannes Kepler
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Europa (moon) [SEP] Atmosphere
Molecular hydrogen never reaches the surface, as it is light enough to escape Europa's surface gravity. Observations of the surface have revealed that some of the molecular oxygen produced by radiolysis is not ejected from the surface. Because the surface may interact with the subsurface ocean (considering the geological discussion above), this molecular oxygen may make its way to the ocean, where it could aid in biological processes. One estimate suggests that, given the turnover rate inferred from the apparent ~0.5 Gyr maximum age of Europa's surface ice, subduction of radiolytically generated oxidizing species might well lead to oceanic free oxygen concentrations that are comparable to those in terrestrial deep oceans.