Seismic detection of a deep mantle discontinuity within Mars by InSight

The paper “Seismic detection of a deep mantle discontinuity within Mars by InSight” led by Quancheng Huang is out!

Summary: The depth and sharpness of a midmantle seismic discontinuity, associated with the phase transition from mineral olivine to its higher-pressure polymorphs, provide essential clues to understanding the temperature and composition of Martian mantle. Using data from NASA’s InSight mission, we examined five marsquakes located 3,400 to 4,400 km away from the InSight lander and observed triplications of the P and S waves that resulted from the interaction with a seismic discontinuity produced by the postolivine transition. Our observations indicate that the Martian mantle is more iron rich than Earth,and both planets have a similar potential temperature. Our geodynamic modeling further constrains the mantle composition and surface heat flow and indicates that the mantle was cold in the early Noachian.

Huang, Q., N.C. Schmerr, S.D. King, D. Kim, A. Rivoldini, A. Plesa, H. Samuel, R.R. Maguire, F. Karakostas, V. Lekić, C. Charalambous, M. Collinet, R. Myhill, D. Antonangeli, M. Drilleau, M. Bystricky, C. Bollinger, C. Michaut, T. Gudkova, J. C.E. Irving, A. Horleston, B. Fernando, K. Leng, T. Nissen-Meyer, F. Bejina, E. Bozdağ, C. Beghein, L. Waszek, N. C. Siersch, J.-R. Scholz, P. M. Davis, P. Lognonné, B. Pinot, R. Widmer-Schnidrig, M. P. Panning, S. E. Smrekar, T. Spohn, D. Giardini, W. B. Banerdt, Seismic detection of the Martian mantle transition zone by InSight, PNAS, doi: 10.1073/pnas.2204474119

https://www.pnas.org/doi/10.1073/pnas.2204474119

Ray path geometry and predicted travel times of mantle triplications in Mars. Teleseismic ray paths of (A) P waves and (B) S waves interacting with the discontinuities in the midmantle, colored according to their bottoming depths. Triplications formed between 60° and 85° from the InSight lander (blue triangle). Pink stars indicate the locations of five LF and BB events which are calculated from

t_{S} - t_{P}

measurements using the EH45coldCrust1 model and assuming a 30-km source depth. Reduced travel time curves (time–distance/velocity) of (C) P and (D) S triplications predicted from the EH45TcoldCrust1 model. Reduction velocities are 12 and 6.5 km/s for P and S waves, respectively. Branches A to C correspond to triplications from ∼800 km depth (associated with the opx to HP-cpx transition), and branches C to F correspond to triplications from ∼1,000 km depth (associated with the postolivine transition). The gray dashed lines highlight the epicentral distances of five LF and BB events.