Modélidation de la propagation des ondes sismiques et des ejecta dans les astéroïdes: application à l'érosion des cratères de l'astéroïde 433-Eros

Céline Blitz 1
1 Magique 3D - Advanced 3D Numerical Modeling in Geophysics
LMAP - Laboratoire de Mathématiques et de leurs Applications [Pau], Inria Bordeaux - Sud-Ouest
Abstract : This PhD describes the application of seismology to asteroids, with two main objectives: estimating the behavior of an asteroid following the occurrence of a seismic excitation and explaining the deficit in small craters observed on asteroid 433 Eros. This asteroid, imaged in the years 2000-2001 by the NEAR spacecraft, exhibits a surface covered by regolith (loose material resulting from rocks crushed by impacts) but depleted in craters with a diameter lower than 200 m (Chapman et al., 2002). The first objective consists in simulating the vibrations triggered by a seismic source for 2-D and 3-D models of the asteroid Eros based on the spectral-element numerical method (e.g., Komatitsch et Tromp, 1999).This method approximates the solution of the seismic wave equation on a mesh of the object under study. The simulations that we performed for different models of asteroid Eros suggest that the regolith layer has an important effect by acting as a wave guide and increasing the amplitude of the seismic signals at the surface of the models. We also show that the presence of a regolith layer reduces the importance of the details of the internal structure of the asteroid, such as the presence of a fracture network. The second objective consists in explaining the observed deficit in small craters on asteroid Eros. The simulation of crater infilling by the deposit of ejecta resulting from impacts explains only part of the erased craters (Blitz et al., 2009). We therefore simulated an impact-induced seismic shaking erasure process that triggers slumping on crater walls (Richardson et al., 2005). The simultaneous action of these two erasure processes (ejecta coverage and seismic shaking) results in a crater population curve that is close to the observed data for an exposure time of about 600 Ma in the Main Asteroid Belt.
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Submitted on : Tuesday, December 15, 2009 - 1:05:59 PM
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Céline Blitz. Modélidation de la propagation des ondes sismiques et des ejecta dans les astéroïdes: application à l'érosion des cratères de l'astéroïde 433-Eros. Sciences de la Terre. Institut de physique du globe de paris - IPGP, 2009. Français. ⟨tel-00441253⟩

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