AbstractsAstronomy & Space Science

Europa, the second of Jupiter’s Galilean moons, has attracted strong interest from the scientific community. This is because it could harbour a sub-surface ocean of liquid water beneath its icy surface, which could be habitable. Recent observations indicate the existence of water vapour plumes at Europa’s south pole. The in-situ measurements of the plume particles (both neutral and ionized) may allow the direct sampling of Europa’s (potentially habitable) sub-surface ocean environment, without the need of an expensive landing or surface-ice penetrating mission. The instrument that could be able to perform in-situ sampling of the plumes is PEP (Particle Environment Package). PEP has been selected to fly on-board the European Space Agency's JUICE mission (JUpiter ICy moons Explorer) to be launched in 2022. PEP is under development now at the Swedish Institute of Space Physics (Institutet för rymdfysik or IRF) in Kiruna, Sweden. PEP is an instrument suite with six sensors to characterize the plasma and neutral environment in the Jovian system in-situ and remotely (via fast neutral imaging). The JUICE mission will perform two flybys of Europa. Related to the development of PEP and future observations of Europa’s plumes a Master’s thesis project with the following goal has been proposed: “Determine if PEP can observe Europa's water vapour plume by modelling: (a) the trajectories of neutral and ionized particles from Europa’s water vapour plumes with test-particle simulations and (b) the respective instrument observation.” In the test-particle simulations method the trajectories of particles through background electric and magnetic fields are determined by treating each particle as an isolated test particle. The project focusses on the JDC (Jovian plasma Dynamics and Composition analyser) and NIM (Neutral and Ion Mass Spectrometer) sensors that are part of PEP. We developed a model of the neutral and ionized plume particle environment. We simulated observations of these particles with respectively the NIM and JDC sensor, and demonstrated observations of plume particles is possible even for plumes that have lower mass flux (≲ 1 kg/s) than what has been observed (7000 kg/s). The developed neutral plume particle model is applicable when the particles in the plume are non-collisional. The ionized plume particle model is applicable to the case where the plume ion density is lower than the typical ion density at Europa. This limits the applicability to plumes with a mass flux ≲ 1 kg/s. We argue that future Europa plume models should consider the collisions between plume particles. Furthermore the expected high ion density will strongly influence the electric fields at Europa, this effect should be taken into account.