| Summary: | Observations of Europa’s leading hemisphere reveal elevated H _2 O _2 in the warmer, low-latitude chaos terrains compared to the colder, polar regions. This distribution disagrees with prior laboratory radiolysis studies of pure water ice, which show higher H _2 O _2 yields at colder temperatures. The regions with higher peroxide abundance, Tara and Powys Regiones, also present increased amounts of CO _2 , possibly sourced from Europa’s interior. To investigate whether CO _2 influences radiolysis of water ice to boost H _2 O _2 production, we irradiated water ice doped with varying amounts of CO _2 with 10 keV electrons at 70 and 100 K. Our results indicate that CO _2 , even in trace amounts (<3%), significantly enhances H _2 O _2 yields at temperatures relevant to Europa. We discuss the mechanisms by which CO _2 boosts peroxide synthesis and quantify H _2 O _2 creation and destruction cross sections and G -values across different CO _2 concentrations. These findings provide a plausible explanation for the perplexing H _2 O _2 distribution on Europa and has implications for understanding peroxide on other icy bodies such as Ganymede and Charon, where it has been detected alongside CO _2 .
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