3D Monte-Carlo Simulation of Ganymede’s Water-Related Exosphere
- 1Physics Institute, University of Bern, Bern, Switzerland (audrey.vorburger@unibe.ch)
- 2Department of Physics, University of Umeå, Umeå, Sweden
- 3Space and Plasma Physics, KTH Royal Institute of Technology, Stockholm, Sweden
Ganymede’s water exosphere has been observed spectroscopically on several occasions since the first detection of atomic hydrogen in Ganymede’s exosphere in 1997 [1]. From these observations a consistent picture of Ganymede’s exosphere has emerged: Ganymede’s day-side exosphere is dominated by sublimated water with inferred column densities of up to several 1e15 cm-2, while elsewhere the exosphere is dominated by sputtered molecular oxygen (inferred column densities of several 1e14 cm-2) at low altitudes and by atomic oxygen (inferred column densities of several 1e13 cm-2) at higher altitudes [2-9]. In addition, atomic hydrogen has been observed with inferred column densities of a few 1e12 cm-2 [1, 4, 10]. Whereas many modeling approaches have been able to reproduce the inferred H2O and O2 densities, they have struggled to re-create the high inferred atomic oxygen and hydrogen column densities [11-13].
In this work, we present new simulations of Ganymede’s water-related exosphere. Our modeling results reproduce the observed H2O emissions well by sublimating water at Ganymede’s day-side surface temperature. The observed OI emission lines, which were interpreted as an O2 atmosphere, on the other hand, agree with a sputter source, with Jupiter’s magnetospheric plasma acting as the sputter agent.
Ganymede has a complex magnetic field, that shields part of the surface (mainly the equatorial regions) from impinging plasma ions and electrons, leaves the polar caps exposed to unhindered plasma precipitation, and accelerates the precipitating plasma in the separatrix, resulting in strong auroral emissions [2-8]. We show that the thermal electrons reaching the polar caps are insufficient to produce the amount of atomic oxygen and hydrogen inferred from the observations, and that an interaction between the water atmosphere and auroral electrons is necessary. In addition, we will discuss how the Particle Environment Package [14] onboard ESA’s JUpiter and ICy moons Explorer [15] will help us learn more about Ganymede’s atmosphere and plasma environment.
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How to cite: Vorburger, A., Fatemi, S., Galli, A., Carberry Mogan, S., Roth, L., and Wurz, P.: 3D Monte-Carlo Simulation of Ganymede’s Water-Related Exosphere, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-635, https://doi.org/10.5194/epsc2022-635, 2022.
