Ocean-sourced CO2 inflates radiolytic H2O2 at Europa’s Chaos

JWST observations of Europa’s leading hemisphere show excess CO₂ over chaos terrains where the ocean is likely to have breached the ice shell. Analysis of the 3.5 µm peroxide absorption reveals elevated amounts of H₂O₂ in these chaos regions. Laboratory experiments motivated by these observations show that trace inclusions of CO₂ can substantially inflate the radiolytic peroxide yield, more so than in pure water ice. These experiments suggest that endogenic CO₂ amplifies H₂O₂ synthesis in the chaos terrain when processed by Jupiter’s magnetospheric particles. We combine the CO₂-enhanced H₂O₂ yields with the energy dose delivered by the magnetospheric particles onto the leading hemisphere to generate a peroxide distribution map to compare with the observed distribution. Our results suggest that geologic activity at Europa’s chaos conspires with precipitating radiation to contribute to the excess peroxide observed by Webb. The rapid transport of the peroxide to the underlying ocean via brine-percolated conduits underscores strong implications for Europa’s habitability. Additionally, these JWST observations combined with laboratory measurements set the stage for detailed mapping of CO2 (via its 2.7 and ~4.23-4.29 µm absorptions) and H2O2 (via its 3.5 µm absorption) with MISE (Europa Clipper) and MAJIS (JUICE) at unprecedented spatial resolution.