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Extrasolare Planeten und Atmosphären
Institutsplanung und Zentrale Aufgaben
Planetenspektroskopische Labore (Arbeitsgruppe)
Astrobiologische Labore (Arbeitsgruppe)
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Derzeitig angebotene Bachelor- und Masterthesen
Master thesis: Convective heat transport in non-Newtonian fluids
Convection in solid planetary interiors is controlled by both Newtonian and non-Newtonian mechanisms. While in the former the relation between stress and strain is linear, in the latter it follows a power law. Because of computational difficulties, non-Newtonian convection is almost always neglected in numerical simulations, even though it is considered as the principal deformation mechanism acting at relatively low pressures. The thesis work will involve numerical simulations of non-Newtonian convection with the goal to characterize heat transport in these complex fluids and to assess the extent to which Newtonian convection can be used to approximate a non-linear behavior.
Master thesis: Role of variable thermal expansion on the initiation of plate tectonics
The problem of the initiation of plate tectonics regards understanding the conditions, which lead to the formation of weak zones (plate boundaries) that serve as nucleation points for the onset of subduction - the process with which tectonic plates sink into the mantle. The creation of such weak zones can be favoured by a positive feedback exerted by the temperature dependence of the coefficient of thermal expansion, which, however, is generally kept constant in plate tectonics models. The thesis work will involve numerical simulations of visco-plastic convection devoted to assess the importance of variable thermal expansivity in controlling the onset of plate tectonics on terrestrial planets.
Master thesis: Convective mixing in fluids with strongly temperature-dependent viscosity
The quantitative characterization of mixing is fundamental to understand whether and how compositional heterogeneities are preserved or destroyed by thermal convection in planetary mantles. Accurate Lagrangian techniques based on particle tracing have been successfully applied to quantify the mixing properties of the Earth’s mantle. Nevertheless, little attention has been devoted to describe mixing in systems in which a strongly temperature-dependent viscosity leads to the formation of a so-called stagnant lid, an immobile rigid upper layer, which does not participate in convection and characterizes all terrestrial bodies other than Earth. The thesis will require the application of existing techniques (Lyapunov exponents) to quantify the mixing properties of such fluids.
Master thesis: Dynamics and consequences of lunar magma ocean overturn
The composition of the Moon’s surface is best explained by assuming that the satellite was completely molten after its formation and subsequently became solid according to a specific crystallization sequence. The latter predicts the formation of a gravitationally unstable chemical stratification that is prone to overturn. The thesis work will involve numerical simulations of the overturn of this solidified “magma ocean” with the goal to understand its dynamics and the consequences for the generation of the Moon’s surface and crustal materials.
Bachelorarbeit / Praktikum: Parameter study for mantle convection
We have developed a spherical convection model that solves fluid dynamic equations to model the mantle flow in terrestrial planets. Convection processes depend on many parameters, e.g. the ratio of core radius to planetary radius (Rc/Rp), the depth dependence of the viscosity, and the surface temperature, that are often not well constrained. The influence of these specific parameters needs to be studied with a detailed parameter study - necessary to better understand the convection processes. We are looking for a student to perform this kind of parameter study.
Diplom- oder Masterarbeit: Thermal Evolution of Icy Satellites
The icy satellites of Jupiter and Saturn consist of an ice layer (varying from hundred to thousand of kilometers in thickness) on top of a silicate mantle and an iron rich core. Thus, heat from the interior, e.g. due to radioactive elements in the silicate part, is transported through these ice shells. Depending on the efficiency of heat transport, the ice layer may strongly influence the thermal evolution and thereby the volcanic and magnetic field evolution of these bodies. So far, it has been assumed that the ice layer transports very efficiently heat and a possible insulating effect has been neglected in earlier models. We want to expand an existing parameterized convection model to couple the heat transfer in the ice shell with the heat transport in the silicate mantle and the iron rich core. The aim is to examine the influence of an ice layer, e.g. its thickness, on the thermal evolution of icy satellites.
Aktuelle und abgeschlossene Arbeiten
Innerer Aufbau planetarer Körper
Mantelkonvektion in Planeten und Monden
Schwere- und Magnetfelder
Seismologie planetarer Körper
Habitabilität und thermische Evolution
Tektonik planetarer Oberflächen
Modellierung planetarer Oberflächen
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