Towards Planetary Remote-Sensing Seismology: Modeling the Airglow Signature of Venus Quakes

Date: 4/25/2019

Time: 06:00 PM

Room: Fifth Avenue

Performing seismology on Venus is of great interest to understanding the interior structure and the tectonic activity of the planet, which are poorly constrained by available observations. However, the extremely high temperature at the surface is challenging for a long-lived seismic station. Therefore, atmospheric and ionospheric seismology - well-established techniques on Earth - could prove very powerful on Venus, where the coupling between the thick atmosphere and the interior of the planet is strong, about 60 times larger than on Earth.

We propose the detecting quakes using an orbiting camera by observing fluctuations in the day- and night-side infrared airglows, at 4.28 and 1.27 microns, respectively. We first make use of normal-mode summation to compute synthetic seismograms in the high atmosphere of Venus, between 90 and 150 km above the surface, and then derive the induced disturbances on the airglow emission rates. The main effects turn out to be related to vertically propagating acoustic waves induced by the Rayleigh waves traveling at the surface of the planet. The resulting airglow-grams are compared to the expected noise at the camera level, and detection techniques based on the identification of circular waveforms propagating at the speed of surface waves are discussed. An advantage of this observational method is that a single camera images the wavefield, with each pixel acting as a seismometer. Preliminary estimates of detection thresholds indicate that quakes of magnitude larger than 5 to 5.8 could be observed, depending on the wavelength and intensity of airglow emissions. Finally, the propagation of the wavefronts would lead to measurements of the Rayleigh-wave velocity and thus to valuable information about the lithosphere and the upper mantle of Venus.

Presenting Author: Philippe Lognonné

Authors