Seismic detection of a deep mantle discontinuity within Mars by InSight

Huang, Quancheng, Schmerr, Nicholas C., King, Scott D., Kim, Doyeon, Rivoldini, Attilio, Plesa, Ana-Catalina, Samuel, Henri, Maguire, Ross R., Karakostas, Foivos, Lekić, Vedran, Charalambous, Constantinos, Collinet, Max, Myhill, Robert, Antonangeli, Daniele, Drilleau, Mélanie, Bystricky, Misha, Bollinger, Caroline, Michaut, Chloé, Gudkova, Tamara, Irving, Jessica C.E., Horleston, Anna, Fernando, Benjamin, Leng, Kuangdai, Nissen-Meyer, Tarje, Bejina, Frederic, Bozdağ, Ebru, Beghein, Caroline, Waszek, Lauren, Siersch, Nicki C., Scholz, John-Robert, Davis, Paul M., Lognonné, Philippe, Pinot, Baptiste, Widmer-Schnidrig, Rudolf, Panning, Mark P., Smrekar, Suzanne E., Spohn, Tilman, Pike, William T., Giardini, Domenico, and Banerdt, W. Bruce (2022) Seismic detection of a deep mantle discontinuity within Mars by InSight. Proceedings of the National Academy of Sciences of the United States of America, 119 (42). e2204474119.

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Abstract

Constraining the thermal and compositional state of the mantle is crucial for deciphering the formation and evolution of Mars. Mineral physics predicts that Mars' deep mantle is demarcated by a seismic discontinuity arising from the pressure-induced phase transformation of the mineral olivine to its higher-pressure polymorphs, making the depth of this boundary sensitive to both mantle temperature and composition. Here, we report on the seismic detection of a midmantle discontinuity using the data collected by NASA's InSight Mission to Mars that matches the expected depth and sharpness of the postolivine transition. In five teleseismic events, we observed triplicated P and S waves and constrained the depth of this discontinuity to be 1,006 ± 40 km by modeling the triplicated waveforms. From this depth range, we infer a mantle potential temperature of 1,605 ± 100 K, a result consistent with a crust that is 10 to 15 times more enriched in heat-producing elements than the underlying mantle. Our waveform fits to the data indicate a broad gradient across the boundary, implying that the Martian mantle is more enriched in iron compared to Earth. Through modeling of thermochemical evolution of Mars, we observe that only two out of the five proposed composition models are compatible with the observed boundary depth. Our geodynamic simulations suggest that the Martian mantle was relatively cold 4.5 Gyr ago (1,720 to 1,860 K) and are consistent with a present-day surface heat flow of 21 to 24 mW/m².

Item ID: 76386
Item Type: Article (Research - C1)
ISSN: 1091-6490
Keywords: interior of Mars, mantle transition zone, thermal evolution of Mars
Copyright Information: © 2022 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).
Date Deposited: 25 Oct 2022 06:35
FoR Codes: 37 EARTH SCIENCES > 3706 Geophysics > 370609 Seismology and seismic exploration @ 50%
51 PHYSICAL SCIENCES > 5109 Space sciences > 510905 Solar system planetary science (excl. planetary geology) @ 50%
SEO Codes: 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280107 Expanding knowledge in the earth sciences @ 50%
28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280120 Expanding knowledge in the physical sciences @ 50%
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