Global Distribution of the Key Species on the Surface of Europa

Abstract The icy surface of Europa is continuously bombarded by ions and electrons from Jupiter’s magnetosphere. The bombardment of the particles dissociates water molecules on the surface of Europa and introduces impurities to the icy surface. Such processes lead to the generation of the nonwater species on the surface of Europa. These chemical species are closely related to the chemistry of the icy crust and the subsurface ocean, as well as Europa’s habitability. However, our knowledge of the global distribution of these species is limited due to the sparse satellite and telescope observations on Europa. In this study, we combine a Europa plasma model and a chemical-transport model to simulate the global distribution of the key nonwater species on the surface of Europa. The initial results from our model agree well with the existing observations on the distributions of H 2 SO 4 and SO 2 , but they show a significant discrepancy with the observed distribution of H 2 O 2 . Sensitivity tests on the reaction rate coefficients indicate that the simulated global distribution of all three species fits the observations well if the reaction rate coefficients in the ice are reduced by 1 order of magnitude. This finding provides a useful constraint on the rate coefficient of the chemical reactions in the ice. Furthermore, our model predicts that the O 2 on the surface ice of Europa is concentrated on the leading hemisphere. The simulated global distribution of the key species on Europa may provide useful guidance for future missions to Europa, such as Europa Clipper and JUICE.