Modelling Europa’s collisional atmosphere using the DSMC method

Abstract

In this study, we present preliminary results of modelling the potentially collisional atmosphere of the Jovian satellite Europa using the Direct Simulation Monte Carlo (DSMC) method [1]. In the DSMC method particular gas flows are calculated through the collision mechanics of representative atoms or molecules that are subject to binary collisions to simulate macroscopic gas dynamics.NASA's Europa Clipper mission [2] and ESA's JUpiter Icy Moons Explorer (JUICE) [3] will encounter Europa with flybys in the 2030s to sample the atmosphere of the icy moon using mass spectroscopy. Measurements with the MAss Spectrometer for Planetary EXploration (MASPEX) onboard Europa Clipper and the Neutral gas and Ion Mass spectrometer (NIM) onboard JUICE will determine the composition of Europa's exosphere and, potentially, sample the plume material. From the exosphere measurements, the chemical composition of Europa's surface could be derived, whereas plume measurements would potentially allow conclusions about the chemical conditions of Europa's subsurface ocean.Models of the collision-less exosphere for the icy moon [4, 5] have shown that Europa’s ice-sputtered atmosphere is dominated by O2 near the surface with an extended H2 corona at higher altitudes. Here, we compare the results of these studies with the DSMC model including deeper layers of Europa's collisional atmosphere.[1] Bird, G. A. (1994). Molecular gas dynamics and the direct simulation of gas flows.[2] Phillips, C. B., and Pappalardo, R. T. (2014). Eos, Transactions AGU, 95(20), 165-167.[3] Grasset, O., et al. (2013). Planetary and Space Science, 78, 1-21.[4] Vorburger, A., and Wurz, P. (2018). Icarus, 311, 135-145.[5] Vorburger, A., and Wurz, P. (2021). J. Geophys. Res. Space Phys., 126(9), e2021JA029690.