[P-PS06] Mars and martian moons

[PPS06-06] Assessment of two-dimensional ground rigidity around the InSight landing site via compliance analysis on Martian convective vortices

Ryoji Otsuka^1,2, *Keisuke Onodera^3,4, Satoshi Tanaka², Taichi Kawamura⁴, Kiwamu Nishida³ (1.Department of Complexity Science and Engineering, The University of Tokyo, 2.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3.Earthquake Research Institute / The University of Tokyo, 4.Institut de Physique du Globe de Paris, Université Paris Cité)

Keywords:InSight, Mars, Atmosphere-ground coupling, Planetary seismology

The internal structure is one of the most important pieces of information for understanding the origin and evolution of a planet. In particular, the near-surface structure strongly reflects past geological activities, such as tectonics and volcanism. NASA's InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission, which aimed at revealing the Martian seismicity and the internal structure, quasi-continuously monitored ground motions, atmospheric pressure, wind speed and direction, and temperature until the end of December 2022 (e.g., Lognonné et al., 2023). Simultaneously, the data of the surface environment around the InSight lander has been acquired from panoramic images captured by InSight as well as from orbital images by Mars Reconnaissance Orbiter.

So far, several studies estimated the shallow subsurface structures at the InSight landing site. Taking Kenda et al. (2020) as an example, they evaluated the rigidity structure down to 20 m by measuring the ground response against external pressure variations caused by convective vortices. More recently, Onodera et al. (2023) improved their model and provided a rigidity structure up to 100 m depth. While their model is limited to 1-D, this study is trying to obtain the 2-D rigidity map to better illustrate the subsurface environment at the InSight landing site.

In this study, we estimated the direction of tilt of the seismometer from the ground acceleration data at the time of convective vortex passage and estimated the azimuth at a vortex's closest approach. Then, for each azimuth, we calculated "compliance" (the spectral ratio of ground motion against pressure fluctuation) and produced a two-dimensional map of Young's modulus near the InSight landing site.

In the presentation, we will discuss the two-dimensional subsurface structure at the InSight landing site, referring to the results of this study and previous studies (e.g., Murdoch et al. 2021; Golombek et al. 2020; Warner et al. 2022).

References:
•Golombek et al. (2020), Nat. Commun., 11, 1014.
•Kenda et al. (2020), J. Geophys. Res. Planets, 125, e2020JE006387.
•Lognonné et al. (2023), Annu. Rev. Earth Planet. Sci., 51, 643-670.
•Murdoch et al. (2021), J. Geophys. Res. Planets, 126, e2020JE006410.
•Onodera et al.(2023), J. Geophys.Res.Planets,128,e2023JE007896.
•Warner et al. (2022), J. Geophys. Res. Planets, 127, e2022JE007232.