Laboratory predictions for the night-side surface ice glow of Europa

Europa’s surface continuously experiences high fluxes of charged particles due to the presence of Jupiter’s strong magnetic field. These high-energy charged particles, including electrons, interact with ice- and salt-rich surface, resulting in complex physical and chemical processes. Here we report that Europa ice analogs emit characteristic spectral signatures in the visible region when exposed to high-energy electron radiation. The strongest emission (ice glow) we observed was centered at ~525 nm. We found that the presence of sodium chloride and carbonate strongly quenched, while epsomite enhanced, the radiation-induced ice glow. These emission characteristics could be used to determine the chemical composition of Europa’s surface during night-time low-altitude flybys of spacecraft such as the Europa Clipper. We estimate that the Europa Clipper Wide Angle Camera could record between 500 and 280,000 counts per second through different color filters, depending on the chemical composition of Europa’s surface. Though we focus here on Europa, our study may be relevant to other bodies exposed to high doses of ionizing radiation, such as Io and Ganymede. With its extreme radiation environment, rich surface geology, and compositional diversity, the radiation-induced ice glow on Europa could enable more precise surface characterization and provide unique night-time views.