[S20-1] Earth and planetary space and remote sensing seismology; i.e., seismology without seismometers

[S20-1-06] Exploring the Use of Airglow Measurements for Detecting Seismicity on Venus

^○Balthasar Kenda^{1, 2}, Philippe Lognonne¹, Attila Komjathy², Bruce Banerdt², Jim Cutts², Lauriane Soret³, Jennifer Jackson⁴ (1.Institut de Physique du Globe de Paris, Paris, France, 2.Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA, 3.Universite de Liege, Liege, Belgium, 4.California Institute of Technology, Pasadena, USA)

Investigating seismology on Venus is expected to greatly improve our knowledge of the internal structure and present-day activity of the planet: these are indeed poorly constrained by observations. However, classical seismology is currently unattainable due the extreme surface temperatures and high atmospheric pressure. Nonetheless, the thick and dense atmosphere is strongly coupled to the ground and therefore Venus is an excellent candidate for atmospheric remote-sensing seismology.

The nightside of Venus is characterized by a bright airglow layer of atomic oxygen at 90-120 km altitude and we explore the possibility of detecting fluctuations in the airglow intensity induced by quakes. On Earth, airglow response to tsunamis has been measured both with ground-based (Makela et al., 2011) and satellite (Yang et al., 2017) techniques. Here, we computed seismograms inside the airglow layer using normal-mode summation for a fully coupled atmosphere-solid planet system (Lognonne et al., 2016). The corresponding variations in the volumetric emission rate are calculated for a realistic background model (Soret et al., 2012) and vertically integrated to reproduce the signals that would be seen from orbit. The noise level of existing airglow cameras suggests that the fluctuations coupled to Rayleigh waves generated by quakes of magnitude 5 and above occurring on the nightside of the planet may be detectable up to about 60 degrees in epicentral distance. A major advantage of this technique is that a single orbiting camera may be sufficient to serve the role of a seismic network. Identification and tracking of the waves will indeed lead to source localization, magnitude estimation and measurement of Rayleigh-wave velocity. In particular, it is expected that this would significantly constrain seismicity on Venus and, through Rayleigh-wave dispersion, the structure of the crust and upper mantle.