Geophysical evidence for an enriched molten silicate layer above Mars's core.

Autor: Samuel H; Université Paris Cité, Institut de physique du globe de Paris, CNRS, Paris, France. samuel@ipgp.fr., Drilleau M; Institut Supérieur de l'Aéronautique et de l'Espace ISAE-SUPAERO, Toulouse, France., Rivoldini A; Royal Observatory of Belgium, Brussels, Belgium., Xu Z; Université Paris Cité, Institut de physique du globe de Paris, CNRS, Paris, France., Huang Q; Department of Geophysics, Colorado School of Mines, Golden, CO, USA.; University of Maryland, College Park, MD, USA., Garcia RF; Institut Supérieur de l'Aéronautique et de l'Espace ISAE-SUPAERO, Toulouse, France., Lekić V; University of Maryland, College Park, MD, USA., Irving JCE; School of Earth Sciences, University of Bristol, Bristol, UK., Badro J; Université Paris Cité, Institut de physique du globe de Paris, CNRS, Paris, France., Lognonné PH; Université Paris Cité, Institut de physique du globe de Paris, CNRS, Paris, France., Connolly JAD; ETH Zurich, Zurich, Switzerland., Kawamura T; Université Paris Cité, Institut de physique du globe de Paris, CNRS, Paris, France., Gudkova T; Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia., Banerdt WB; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.
Jazyk: angličtina
Zdroj: Nature [Nature] 2023 Oct; Vol. 622 (7984), pp. 712-717. Date of Electronic Publication: 2023 Oct 25.
DOI: 10.1038/s41586-023-06601-8
Abstrakt: The detection of deep reflected S waves on Mars inferred a core size of 1,830 ± 40 km (ref. 1 ), requiring light-element contents that are incompatible with experimental petrological constraints. This estimate assumes a compositionally homogeneous Martian mantle, at odds with recent measurements of anomalously slow propagating P waves diffracted along the core-mantle boundary 2 . An alternative hypothesis is that Mars's mantle is heterogeneous as a consequence of an early magma ocean that solidified to form a basal layer enriched in iron and heat-producing elements. Such enrichment results in the formation of a molten silicate layer above the core, overlain by a partially molten layer 3 . Here we show that this structure is compatible with all geophysical data, notably (1) deep reflected and diffracted mantle seismic phases, (2) weak shear attenuation at seismic frequency and (3) Mars's dissipative nature at Phobos tides. The core size in this scenario is 1,650 ± 20 km, implying a density of 6.5 g cm -3 , 5-8% larger than previous seismic estimates, and can be explained by fewer, and less abundant, alloying light elements than previously required, in amounts compatible with experimental and cosmochemical constraints. Finally, the layered mantle structure requires external sources to generate the magnetic signatures recorded in Mars's crust.
(© 2023. The Author(s).)
Databáze: MEDLINE
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