Planetary applications of atmospheric seismology: Signals from the Martian turbulent atmosphere and observation perspectives in Venus’ ionosphere
IPGP - Îlot Cuvier
Soutenances de thèses
Planétologie et sciences spatiales (PSS)
Planetary atmospheres may play an important role in extraterrestrial seismology. Indeed, as in the case of the Earth, atmospheric dynamics contributes to the environmental noise measured by a seismometer, especially if the latter is installed at the very surface. Moreover, seismic waves generated by large quakes are converted into acoustic-gravity waves and are routinely detected in Earth’s ionosphere. In this work, we review the theory describing the coupling between the interior of a terrestrial planet and its atmosphere, both at the small and large scale, and we apply it to Mars and Venus. In the case of Mars, in view of the InSight mission expected to land on November 26 2018, we model the quasi-static ground deformation induced by local pressure fluctuations, focusing on the effects of convective vortices and dust devils, which may be detected by the seismometer every few days. We also develop a pressure-decorrelation method, able to reduce pressure noise by a factor 5-10 in the 20-100 s band. Finally, we discuss strategies to retrieve the structure of the subsurface down to a few tens of meter depth from seismic and meteorological records, mainly through compliance measurements. For Venus, we apply a normal-mode based modeling of the atmospheric waves following a quake, including attenuation effects, and we investigate the seismic signature in the infrared airglow layers at 90-150 km altitude. These airglow fluctuations may be observed by a high-resolution orbiting camera and lead to the detection of quakes with magnitude larger than 5-6, and to the determination of the crustal and lithospheric structure through the measurement of Rayleigh-wave dispersion.