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Theses

Etude du cryovolcanisme sur Europe

Abstract : Europa is a Jupiter’s moon covered with a water-ice layer, hiding a global liquid water ocean approximately 100 km thick. Europa’s interior is heated by the tidal forces induced by Jupiter, that provide enough energy to maintain a vigorous geological activity on this moon. Europa’s surface is very young, with an age estimated around 70-90 Ma, which demonstrates a recent resurfacing of the moon. Various geological features have been identified at Europa’s surface, and some of them, like the smooth plains, domes and chaos might indicate the presence of sub-surface reservoirs of liquid water or brines (cryomagma). In this thesis, we propose a cryovolcanic eruption model from a cryomagma reservoir stored in the ice crust. The overpressure generated during the cryomagma freezing could be high enough to fracture the ice crust and let the cryolava rise toward the surface and spread on it. This predictive model allows us to know the duration of an eruption, and the total cryolava volume erupted as a function of the reservoir depth in the ice crust. It also allows us to calculate the pressure in the reservoir and the fluid velocity in the fracture during the eruption. We investigated the influence of the cryomagma composition and the ice crust rheology on the possibility of an eruption. We finally modeled the deformation of a reservoir stored in a viscoelastic ice crust. A few images taken by the Galileo spacecraft during the 1990’s show quasi-circular smooth features, that may be interpreted as cryolava flows. We wanted to use these images to constrain our eruption model by measuring the volume of these objects. To do this, we generated digital elevation models (DEMs) of these images thank to the photoclinometry technique. We used the AMES StereoPipeline (ASP) tool, provided by the NASA. We estimated the uncertainties on the DEMs produced by the ASP by doing a sensitivity study of this tool. We also measured the volume of four smooth plains and deduced the size of reservoir needed to generate these thanks to our eruption model. Two missions, JUICE (ESA) and Europa Clipper (NASA) will be launch in the next years and should provide new insights on Europa’s sub-surface. In this context, this thesis could help to select the zones the more likely to show biosignatures. The smooth plains studied in this thesis might be linking the interior and the surface of the Europa, which could present a great interest for the future exploration of this moon.
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https://tel.archives-ouvertes.fr/tel-03150075
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Submitted on : Tuesday, February 23, 2021 - 6:15:15 PM
Last modification on : Thursday, February 25, 2021 - 3:26:46 AM

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  • HAL Id : tel-03150075, version 2

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Elodie Lesage. Etude du cryovolcanisme sur Europe. Planétologie et astrophysique de la terre [astro-ph.EP]. Université Paris-Saclay, 2020. Français. ⟨NNT : 2020UPASJ008⟩. ⟨tel-03150075v2⟩

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