SEIS, the French lead international seismometer of NASA’s InSight mission, has operated on Mars until mid-December 2022.  Thanks to a careful robotic installation and wind shielding the Very-Broad-Band sensors of SEIS have reached ultra-low noise (down to 2x10^-10 ms-2 Hz^-1/2 between 0.1-1Hz) during the first half of night. Magnitude detection threshold are M<3 in the InSight hemisphere and M~4 in the antipodal one. Noise was much larger during the rest of each day, exceeding the noise recorded on the Moon but still 10 times less than the quietest sites on Earth in the 0.1-1H bandwidth.

1319 events were detected including a Mw=4.7 marsquake, which excited surface waves and likely normal modes and 90 teleseismic events down to Mw=2.5 and for the 40 largest one with determined distances. About 8 impacts were also confirmed by orbital crater imaging, two with very large craters. About half of the events are located near Cerberus Fossae, which suggest either recent or possibly on-going volcanic seismo-tectonics.

With these seismic events, SEIS has been able to provide the first interior seismic models of the planet, from the 40 km thick crust beneath InSight down to the core. These models revealed the stratigraphy of the crust, including through surface waves anisotropy, the structure and thickness of the thermal lithosphere and the presence of a molten silicate layer at the bottom of the core, beneath a lower partially molten layer. Together with the seismic models of the Moon and Earth, obtained from the Apollo data and the international seismic networks respectively, comparison of these three terrestrial bodies is not possible, for both interior and seismic properties view.

In conclusion, SEIS not only performed the first seismic discovery of the martian interior, but contributed also in some way to the rebirth of planetary seismology. Planetary seismology will indeed continue on the Moon, not only with the  Chang’he 7 & 8 missions and the Artemis-3  LEM experiment, but also with one of the spare unit of the SEIS-VBB sensors, which will be deployed in 2026 by the JPL/CNES/IPGP FarSide Seismic Suite experiment!

These researches have been supported by the French Space Agency (CNES) and MAGIS Project of French National Research Agency (ANR-19-CE31-0008)