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Article Dans Une Revue Nature Année : 2023

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

Henri Samuel
Mélanie Drilleau
Attilio Rivoldini
Zongbo Xu
  • Fonction : Auteur
  • PersonId : 1210868
  • IdHAL : zongboxu
Quancheng Huang
  • Fonction : Auteur
Raphaël F Garcia
Vedran Lekić
  • Fonction : Auteur
Jessica C E Irving
James Badro
James a D Connolly
Taichi Kawamura
Tamara Gudkova
  • Fonction : Auteur
William B Banerdt

Résumé

Abstract 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.
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Dates et versions

hal-04270392 , version 1 (04-11-2023)

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Henri Samuel, Mélanie Drilleau, Attilio Rivoldini, Zongbo Xu, Quancheng Huang, et al.. Geophysical evidence for an enriched molten silicate layer above Mars’s core. Nature, 2023, 622 (7984), pp.712-717. ⟨10.1038/s41586-023-06601-8⟩. ⟨hal-04270392⟩
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