Ocean-sourced CO2 Boosts Radiolytic Oxidants at Europa’s Chaos

Abstract James Webb Space Telescope (JWST) observations of Europa’s leading hemisphere reveal enhanced CO 2 abundances over equatorial chaos terrains where the subsurface ocean is thought to have breached the ice shell. Hydrogen peroxide, synthesized radiolytically by Jovian magnetospheric charged particles impinging on Europa’s ice, is also elevated in these geologically active regions, spatially coinciding with CO 2 . This correlation implicates CO 2 in H 2 O 2 synthesis, consistent with laboratory experiments showing increased radiolytic peroxide yields in carbon-bearing ices. Our radiolysis model – which incorporates charged-particle precipitation through electromagnetic fields accounting for Europa’s interaction with Jupiter’s magnetosphere – predicts enhanced H 2 O 2 on the leading hemisphere equatorial regions. The relative dearth of energetic electrons in this region shields peroxide from destruction, leaving a notably higher abundance towards the leading apex compared to the mid-latitude regions or the trailing side. Integrating the inferred CO 2 abundance and the associated boost in peroxide yield, we show that ocean-derived CO 2 acts as a multiplier, further elevating H 2 O 2 concentrations within the fractured surfaces of Tara and Powys Regiones. Together, these results imply that geologic resurfacing at Europa’s chaos terrains and precipitating radiation conspire to contribute to the excess peroxide observed by JWST, with endogenic CO 2 amplifying oxidant production in these potentially ocean-linked regions.