Oxygen Sources on Europa
Abstract
Europa, one of the Galilean satellites, has a tenuous, oxygen-dominated atmosphere that is usually referred to as a collision-less exosphere. It's generally understood that the primary source of oxygen is the sputtering of Europa's surface ice by energetic particles coming from the Jovian magnetosphere, particularly the positive ions such as H+, O+, and S+. However, high-energy (hundreds of keV to tens of MeV) electrons in the Jovian magnetosphere are able to dissociate water molecules when bombarded on Europa's surface ice and produce oxygen inside the ice, which can diffuse radially inward and outward. Oxygen diffusing outwards can be regarded as an oxygen source that contributes to the atmosphere. Observations have also revealed the presence of a tenuous ionosphere on Europa in contact with the surface and coupled to the neutral atmosphere. Such an ionosphere is thought to be produced by solar photoionization and electron-impact ionization of the oxygen in the atmosphere. However, a recent study showed that the maximum ionosphere coincides with intermittent water plume on Europa, suggesting that water plays an important role in the formation of the ionosphere. Therefore, there may be another oxygen source initiated by water photolysis and photoionization. Here, we use a 1D chemical-transport model KINETICS to simulate the photochemical and electron-impact reactions in Europa's atmosphere. These two oxygen sources together will provide a better understanding of the different processes that are happening in both Europa's atmosphere and surface ice. The study also has implications for the chemical composition of Europa's subsurface ocean, and may give us insight into Europa's habitability and suggestions for future measurements.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.P11C3474L
- Keywords:
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- 1060 Planetary geochemistry;
- GEOCHEMISTRY;
- 5210 Planetary atmospheres;
- clouds;
- and hazes;
- PLANETARY SCIENCES: ASTROBIOLOGY;
- 5220 Hydrothermal systems and weathering on other planets;
- PLANETARY SCIENCES: ASTROBIOLOGY;
- 5419 Hydrology and fluvial processes;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS