10.03 - Planetary Seismology | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS


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  10.03 - Planetary Seismology

Type de publication:

Book Chapter


Treatise on Geophysics (Second Edition), Elsevier, Oxford, p.65 - 120 (2015)








<p>Abstract To date, successful in situ extraterrestrial seismic measurements have been limited to data collected during the Apollo lunar missions. These data have significantly contributed to our understanding of the Moon's interior structure, leading to the development of feasible thermal and mineralogical models. In addition, the seismic activity recorded by the Apollo stations has provided information on both internal (moonquakes) and external (meteoroid) sources of seismic activity. The seismic activity of other extraterrestrial bodies, notably Mars and Venus, has never been directly measured. It can be estimated, however, using approximations of those bodies’ lithospheric thermal structures, strain rates, and plausible present-day tectonic activity. Both Mars and Venus likely experience events that would be detectable by surface seismometers. Mars is estimated to endure 50 (respectively 10) quakes annually with moment magnitudes (Mw) greater than 3.8 (respectively 4.5). In addition, impacts large enough to create seismic effects may occur at a rate comparable to the Moon’s impact rate. Meanwhile, Venus experiences an estimated 100(25) quakes annually with Mw greater than 5(6). Such seismic activity, which is much larger than the lunar activity, justifies the deployment of seismic monitoring systems on these planets. Mars will most likely be the next new body to be explored using surface landers, with the deployment of a modern geophysical observatory planned for 2016, as part of the InSight mission. Our current understanding of the interior structure, seismic noise levels, and scattering of Mars indicates that body-wave and regional surface-wave investigations could yield enormous insight into the structure and evolution of this planet. Asteroids or icy satellites, such as Europa, might also provide productive targets for passive seismic experiments, and returning to the Moon with more sensitive seismometers could yield additional knowledge as well. The deployment of surface landers with long-lasting instruments might be much more difficult on Venus, given the planet's high surface temperature. But the acoustic coupling of a planet's atmosphere with its internal body provides opportunities for seismic investigations, and the coupling effect can be exploited on Venus, which is a planet with a dense atmosphere, or on the giant planets. On Venus, signals at a given height in the atmosphere for a given quake magnitude can have amplitudes 600 × their terrestrial counterparts for a given quake seismic moment. Detecting Venusian quakes from orbit can be achieved by analyzing the near-source thermal and albedo signatures and ionospheric perturbations associated with Rayleigh waves. Detecting the normal modes of Jupiter and other giant planets, on the other hand, might be possible through the use of ground- or space-based techniques, and these techniques may allow for the future exploration of the giant planets’ interiors.</p>