Can endogenic CO2 inflate radiolytic H2O2 in Europa’s Chaos?

Recent JWST observations reveal a higher abundance of endogenic CO2 at Tara Regio, a prominent leading hemisphere chaos (Villanueva et al., 2023; Trumbo and Brown, 2023). Prior findings from Keck also show an excess of H2O2 in the same region (Trumbo et al., 2019). Could the emplacement of the ocean-derived CO2 onto Europa’s surface influence radiolytic chemistry to boost peroxide yields in these enigmatic chaos regions? Increased H2O2 at fractured chaos terrains where ocean-surface exchange is more likely is exciting from a habitability stance, as it may facilitate oxidant delivery to the subsurface ocean. We present laboratory results that show H2O2 synthesis increases by 2-3 folds in the presence of trace amounts of CO2 (< 3 %) when compared to radiolysis of pure water ice. We also discuss correlations between CO2 and H2O2 abundances in the JWST datasets to determine whether Europa’s endogenous CO2 indeed conspires to inflate H2O2 at Tara Regio and possibly other chaos terrains. These JWST observations combined with emerging 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. References: Villanueva, G. L. et al., (2023) Science, 381, 1305–1308  Trumbo, S. K and Brown, M. E. (2023) Science, 381, 1308–1311 Trumbo, S. K. et al. (2019) Astronomical Journal, 158, 127