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Orbital and internal dynamics of terrestrial planets
Walterová, Michaela ; Běhounková, Marie (advisor) ; Efroimsky, Michael (referee) ; Brož, Miroslav (referee)
Title: Orbital and internal dynamics of terrestrial planets Author: Michaela Walterová Department: Department of Geophysics Supervisor: RNDr. Marie Běhounková, Ph.D., Department of Geophysics Abstract: Close-in exoplanets are subjected to intense tidal interaction with the host star and their secular evolution is strongly affected by the resulting tidal dissipation. The tidal dissipation not only provides an additional heat source for the planet's internal dynamics but it also contributes to the evolution of the planet's spin rate and orbital elements. At the same time, the tidal dissipation itself is also determined by the planet's thermal state and by the spin-orbital parameters. The evolutions of the orbit and of the interior are, therefore, intrinsically linked. In this work, we combine analytical and numerical techniques to gain insight into the interconnection between the internal properties and the orbital evolution, with special focus on the role of tides. After a general study of parametric dependencies of the tidal heating and tidal locking, we present a semi-analytical model assessing the coupled tidally-induced thermal-orbital evolution in systems consisting of a host star and one or two planets. Specifically, we study the thermal-orbital evolution in three systems inspired by existing low-mass...
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Evolution of magmatic oceans in tidally heated terrestrial exoplanets
Verkinová, Natália ; Běhounková, Marie (advisor) ; Čížková, Hana (referee)
The thesis focuses on the study of terrestrial exoplanets that are tidally heated, which can give rise to the formation of magma oceans. The primary objective is to analyze the impact and evolution of the magma ocean and thermal processes in two distinct celestial bodies: an Earth-like body and an Io-like body. We model parametrical evolution of thermal and tidal dissipation that are coupled. As part of the thesis, we investigated the influence of orbital, rheological parameters and the effect of surface temperature on the thermal evolution of the mantle. We included scaling relations developed for models heated from below as well as from within. If the tidal heating is sufficiently intense to induce the presence of a molten layer within the body, then mechanical decoupling of part of the mantle occurs, and thus the tidal response changes and less energy starts to dissipate in the body. Two possible cases have been considered for melt distribution: the case where all the melt is retained in the mantle, and the case where some of the melt reaches the surface and hence more efficient heat transfer occurs. 1
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Hydrosphere structure of icy satellites
Košíková, Terézia ; Běhounková, Marie (advisor) ; Kalousová, Klára (referee)
The exploration of potential life on other celestial bodies within the Solar System is one of the key questions in planetary science. In this work, we focused on determining the hydrosphere of the icy moons Ganymede and Europa in order to determine possible obstacles in habitability due to the presence of the high-pressure ices. We used known thermodynamic properties and satellite parameters to create an algorithm that deter- mined their structures. We found that on Ganymede high-pressure ices are present in a wide range of pressure and temperature conditions, which may prevent the transfer of minerals between the silicates and the subsurface ocean. For Europa, we found that the occurrence of high-pressure ice phases is very unlikely in its hydrosphere. However, the latest data for Europa complicates the exact determination of its structure and Europa may contain thinner hydrosphere and ocean than originally thought. 1
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Insolation pattern and surface temperature on extrasolar planets
Káňová, Michaela ; Běhounková, Marie (advisor) ; Čadek, Ondřej (referee)
We study evolution and distribution of surface and near-surface temperature on tidally locked extrasolar terrestrial planets without atmosphere. In order to determine the temperature, insolation patterns depending on eccentricity, obliquity and spin-orbit resonance are computed and thermal diffusion equation is solved in a spherical shell. We discuss the dependence of temperature distribution on physical and geometrical parameters including orbit eccentricity, obliquity of rotational axis, type of spin-orbital resonance, thermal inertia and irradiance incident on the planetary surface (the extra- solar constant). The mean annual temperature is driven especially by the extrasolar constant and may rise up to thousand of kelvins in the most irradiated regions. Effect of eccentricity, obliquity and thermal inertia, in some cases, is on the scale of hundreds of kelvins.
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Evolution of terrestrial exoplanets
Káňová, Michaela ; Běhounková, Marie (advisor) ; Čadek, Ondřej (referee)
Observations of terrestrial exoplanets provide a unique statistical set that may improve our knowl- edge of their formation, structure as well as internal and orbital evolution. Close-in extrasolar planets are subjected to strong stellar tides, resulting in an extensive dissipation of mechanical energy (tidal heating), long-term orbital evolution and evolution of the rotational frequency. For the exoplanets on eccentric orbits, the traditional tidal theories predict locking into pseudo-synchronous spin states, for which the rotational frequency is slightly higher than the orbital frequency. Such predictions are, how- ever, in contradiction with the observations of moons in the Solar system, and are a consequence of simplified rheological assumptions. Here, we focus on a numerical approach to the tidal evolution of planetary orbit and rotation in a single-planet system, assuming a Maxwell viscoelastic rheology. We find equillibrium spin states, including the spin-orbit resonances, and discuss their connection with the minima of tidal heating. Locking into a spin-orbit resonance results in an irregular insolation pattern and an unequal surface temperature distribution, affecting the internal dynamics of the planet. The second part of the thesis therefore deals with the evaluation of the surface temperature and...
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Viscoelastic deformation of ice bodies in the Solar System
Kihoulou, Martin ; Kalousová, Klára (advisor) ; Běhounková, Marie (referee)
Two icy bodies of the Solar System, a moon of Saturn Titan and a dwarf planet Pluto, are studied in this thesis. Titan's polar radius is smaller than expected, which can be explained by soaking of the ethane rain followed by methane- ethane substitution in the crust. We treat the crust as continuum with viscoelastic (Maxwell) rheology and solve its loading by spectral method. We obtain results in agreement with those published. On Pluto, the position of Sputnik Planitia crater close to the tidal axis might be a sign of subsurface ocean. This unlikely location can be explained by reorientation of the body, if the gravity anomaly of the crater is positive. This requires isostatic compensation, which would mean a material denser than ice, e.g. water, filling the lower crater. Solving by spectral method we obtain results consistent with the hypothesis. However, solving viscous deformation in domain with free surface by finite element method indicates that the lower crater relaxes too fast to explain reorientation. 1
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Anelastic deformation of planetary bodies
Vach, Dominik ; Čadek, Ondřej (advisor) ; Běhounková, Marie (referee)
Observations indicate an existence of subsurface oceans for some of the icy moons in the Solar System which are heated by the tidal forces. In order to describe this anelastic deformation, the methods well-known from the continuum mechanics were employed, and thus the dissipation was calculated for various bodies. In the thesis, Maxwell and Kelvin-Voigt model were compared in their ability to predict the heating power of the bodies. In contrast to the Maxwell model, the Kelvin-Voigt model, which is generally not used in geophysics, repre- sents reversible processes, and thus could explain the effects which are otherwise explained only by the gravity. A program in Fortran was developed in order to compare the models by modelling 3D anelastic deformation of planetary bodies under the effect of tidal forces. The results indicate the predicted power can be various for both models and Kelvin-Voigt model could be used e.g. to describe short run deformation processes. 1
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