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 boundary2. 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 layer3. 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.
| Original language | English |
|---|---|
| Pages (from-to) | 712-717 |
| Number of pages | 6 |
| Journal | Nature |
| Volume | 622 |
| Issue number | 7984 |
| Early online date | 25 Oct 2023 |
| DOIs | |
| Publication status | Published - 26 Oct 2023 |
Bibliographical note
Funding Information:We acknowledge NASA, CNES, partner agencies and institutions (UKSA, SSO, DLR, JPL, IPGP-CNRS, ETHZ, ICL and MPS-MPG), and the operators of JPL, SISMOC, MSDS, IRIS-DMC and PDS for providing SEED SEIS data. H.S. and M.D. were granted access to the GENCI HPC resources of IDRIS under allocations A0110413017 and A0110412958. Numerical computations were partly performed on the S-CAPAD/DANTE platform, IPGP, France, and on GINZA GA-HI supercomputing facilities. Co-authors affiliated to French laboratories thank the French Space Agency CNES and ANR fund (ANR-19-CE31-0008-08). J.B. acknowledges support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 101019965-ERC advanced grant SEPtiM). Additional support was obtained from IdEx Université Paris Cité ANR-18-IDEX-0001 for H.S., Z.X., P.H.L., J.B. and T.K. V.L. acknowledges support from NASA grant 80NSSC18K1628 and NASA SSERVI Cooperative Agreement 80NSSC19M0216. J.C.E.I. acknowledges UKSA grant ST/W002515/1. This is InSight Contribution Number 224.
Funding Information:
We acknowledge NASA, CNES, partner agencies and institutions (UKSA, SSO, DLR, JPL, IPGP-CNRS, ETHZ, ICL and MPS-MPG), and the operators of JPL, SISMOC, MSDS, IRIS-DMC and PDS for providing SEED SEIS data. H.S. and M.D. were granted access to the GENCI HPC resources of IDRIS under allocations A0110413017 and A0110412958. Numerical computations were partly performed on the S-CAPAD/DANTE platform, IPGP, France, and on GINZA GA-HI supercomputing facilities. Co-authors affiliated to French laboratories thank the French Space Agency CNES and ANR fund (ANR-19-CE31-0008-08). J.B. acknowledges support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 101019965-ERC advanced grant SEPtiM). Additional support was obtained from IdEx Université Paris Cité ANR-18-IDEX-0001 for H.S., Z.X., P.H.L., J.B. and T.K. V.L. acknowledges support from NASA grant 80NSSC18K1628 and NASA SSERVI Cooperative Agreement 80NSSC19M0216. J.C.E.I. acknowledges UKSA grant ST/W002515/1. This is InSight Contribution Number 224.
Publisher Copyright:
© 2023, The Author(s).