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Surface waves and crustal structure on Mars
D Kim1,2, W B Banerdt3, S Ceylan1
1Institute of Geophysics, ETH Zürich, Zürich, Switzerland.
Science (New York, N.Y.)
|October 27, 2022
Summary
Surface waves from Martian meteorite impacts reveal distinct crustal structures. The crust north of the equatorial dichotomy shows higher density and less variation than beneath the InSight lander.
Area of Science:
- Planetary Science
- Seismology
- Geophysics
Background:
- Understanding Mars's crustal structure is crucial for deciphering its formation and evolution.
- Previous seismic studies on Mars primarily focused on the area beneath the InSight lander.
Purpose of the Study:
- To investigate Martian crustal structure away from the InSight lander using seismic surface waves.
- To determine variations in shear wave velocity and infer properties like density and porosity.
Main Methods:
- Detection and analysis of surface seismic waves generated by two meteorite impacts on Mars.
- Measurement of group velocity dispersion along paths from impact sites to the InSight lander.
- Inversion of seismic data to constrain shear wave velocity structure at various depths.
Main Results:
- Shear wave velocity in the Martian crust north of the equatorial dichotomy (5-30 km depth) is approximately 3.2 km/s with minimal variation.
- This seismic velocity suggests higher crustal density or lower porosity compared to the region beneath the InSight lander.
- The layered, lower-velocity structure observed beneath the InSight lander is not a global characteristic of the Martian crust.
Conclusions:
- Martian crustal structure exhibits significant regional variations, particularly between the equatorial dichotomy and the InSight landing site.
- These findings challenge global models of Martian crustal thickness and formation, highlighting the need for more spatially diverse seismic data.
- Seismic surface wave analysis provides a powerful tool for probing subsurface structures on Mars and other terrestrial planets.
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