The Influence of Non‐Thermal Collisions in Europa's Atmosphere

Abstract

Abstract In this study, we show that non‐thermal collisions can play a significant role in shaping Europa's exospheric structure. Collisions between radiolytically produced O2 and the O produced via electron impact dissociation of O2 affect the exospheric structure and escape rates. Specifically, O + O2 collisions lead to the production of a non‐thermal O2 population, and increase the O2 escape while decreasing the O escape. These collisions are dependent on three specific physical parameters: (a) the density of O2, (b) the electron impact dissociation rate of O2, and (c) the O + O2 collision cross section. We demonstrate here that O + O2 collisions affect Europa's atmosphere even in the lowest limits considered. Thus, to more accurately determine the influence O + O2 collisions have on Europa's atmosphere in preparation for the forthcoming spacecraft missions, Europa Clipper and the JUpiter ICy moons Explorer (JUICE), these physical parameters need to be better constrained.