Upper mantle structure of Mars from InSight seismic data

For two years the InSight lander has been recording seismic data on Mars that are vital to constrain the structure and thermochemical state of the planet. We2used observations of direct (P and S) and surface-reflected (PP, PPP, SS, and SSS) body wave phases from 8 low-frequency marsquakes to constrain the in- terior structure to 800 km depth. We found a structure compatible with a low-velocity zone associated with a thermal lithosphere much thicker than on Earth that is possibly related to a weak S-wave shadow zone at teleseismic distances. By combining the seismic constraints with geodynamic models, we predict that the crust is 13–20 times more enriched in heat-producing elements than the primitive mantle, greater than suggested by gamma-ray surface map- ping, and has a moderate-to-elevated surface heat flow.