Exchange of impact-generated dust between the Galilean moons
1University of Oulu, Faculty of Science, Astronomy
|Online Access:||PDF Full Text (PDF, 7 MB)|
|Persistent link:|| http://urn.fi/URN:NBN:fi:oulu-202004251556
Oulu : K. Matilainen,
|Publish Date:|| 2020-04-27
|Thesis type:||Master's thesis
The dust environment of Jupiter consists of various dynamically different parts: tenuous dust rings around the planet, dust streams emanating from the volcanic plumes of Io, impact-generated dust clouds around the Galilean moons, and dilute populations of dust in the outer parts of the Jupiter system. The main source of dust material in the jovian system is impact ejection from the surface of (especially the smaller) moons, caused by high-velocity micrometeoroid impacts. The dust particles are relatively short-lived, and their orbital evolution is influenced by various different forces, including gravitational forces, solar radiation forces, electromagnetic forces and drag due to plasma in the system.
In the vicinity of the Galilean moons there exists a faint ring, consisting of dust material ejected from the surface of Galilean moons by micrometeoroid impacts. In contrast to the dust detached from the small moons in the inner Jupiter system, most of the material ejected from the Galilean moons moves on ballistic trajectories and re-impacts the surface of the moons. From the dust material ejected from the surface of the Galilean moons, only a small fraction manages to escape into circumjovian orbits. These escaped grains form a broad, but extremely faint ring, concentrated between the orbits of Io and Europa.
Historically, a good majority of research in the Jovian dust environment has focused on the dynamics of the ring system, whereas dust in the vicinity of the Galilean satellites has attracted less attention. However, the measurements in this region by the Galileo dust instrument and the detection of impact-generated clouds have stipulated new interest, especially in view of the forthcoming missions to the Jupiter system, like the Jupiter Icy Moons Explorer by the European Space Administration, and the Europa Clipper -mission by the National Aeronautics and Space Administration, both planned for launch in the 2020s.
The goal of the thesis was to derive the fluxes of dust on the surfaces of each of the Galilean moons, using the results on the dust environment of the moons from the Jovian Meteoroid Environment Model (JMEM). To this end, a program using the software Interactive Data Language was created, that directly employs functions from JMEM and then constructs the fluxes on a given surface element of a moon. To visualize the final results, contour plots of the flux distributions on the surface of the four moons were produced, explaining the effect of different parameters for the dust configuration.
To support the interpretation of the final dustmap results in terms of orbital motion and evolution of dust, a simple analytical model using a fixed semimajor axis and a model distribution of eccentricities for the simulated orbits of dust, was used to produce a theoretical distribution of impact angles of dust on the surface of the Galilean moons. Through the created contour plots, leading-trailing asymmetries for the flux of dust impacting on the surface of the moons were identified and interpreted in light of this analytical model.
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