Ozone Production by Electron Irradiation of Regolith Ice: Laboratory Study for the Icy Moons

We irradiate fine‐grained regolith pure water ice in ultra high vacuum with and electrons to study the radiolysis of water ice. The ice regolith is designed to closely mimic the physical characteristics of the surfaces of the icy moons of the Solar System. We analyze the species sputtered by the electron irradiation using a time‐of‐flight mass spectrometer, recording the mass spectra before and during irradiations. We sublimate the ice with high‐flux irradiations to release the trapped species. We find that oxygen and ozone are produced and stored in the ice. The ozone to molecular oxygen ratio is consistent with the observations of the surface of Ganymede. Since there are no other requirements than electron irradiation and water ice regolith, we expect ozone production to be widespread in the icy bodies in the Solar System.