Experimental constraints on a long-lived magma layer at the Martian core–mantle boundary
8 affiliations
- 1Bayerisches Geoinstitut, Universitaet Bayreuth, Bayreuth, Germany.
- 2Muséum National d'Histoire Naturelle, Sorbonne Université, UMR CNRS 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Paris, France.
- 3Geodynamics Research Center, Premier Institute for Advanced Studies (PIAS), Ehime University, Matsuyama, Japan.
- 4CNR-ISSMC, URT Università degli studi di Roma Tre, Rome, Italy.
- 5Institute of Geochemistry and Petrology, ETH Zürich, Zurich, Switzerland.
- 6Department of Physics and Astronomy, Kwansei Gakuin University, Sanda, Japan.
- 7Japan Synchrotron Radiation Research Institute, SPring-8, Hyogo, Japan.
- 8Institut de Physique du Globe de Paris, Université Paris Cité, CNRS, Paris, France.
Abstract
Geophysical observations from the InSight mission suggest anomalously low seismic velocities near the Martian core–mantle boundary, possibly indicating a molten silicate layer. Such a layer would have major implications for the thermal and chemical evolution of Mars, but its origin remains poorly constrained because experimental data on iron-rich Martian melts at deep-mantle conditions remain scarce. Here we use in situ ultrasonic interferometry combined with X-ray imaging and diffraction to determine the melting phase relations, ultrasonic response and chemical compositions of co-existing melts and solids under conditions relevant to the Martian core–mantle boundary. Our experiments constrain a Martian mantle solidus about 100 K lower than previous estimates. We show that incipient melting rapidly weakens the elastic response, reducing wave speeds and modifying the ultrasonic signal character. Melts generated slightly above the solidus at 18–19 GPa, equivalent to a depth of approximately 1,550 km, are strongly enriched in iron (Fe# of 0.5) and reach densities comparable to or greater than surrounding solids, implying neutral to negative buoyancy. The combination of high melt density and low wetting angles favours the formation of an interconnected dense melt layer near the core–mantle boundary from a moderately FeO-rich Martian mantle without necessarily requiring overturn of an extremely Fe-enriched primordial reservoir and remains compatible with proposed thermal models.
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BibTeX
@article{pierru2026experimental,
title = {{Experimental constraints on a long-lived magma layer at the Martian core–mantle boundary}},
author = {Rémy Pierru and Steeve Gréaux and Serena Dominijanni and Lianjie Man and Yoshio Kono and Sho Kakizawa and Yuji Higo and James Badro and Daniel J Frost and Daniele Antonangeli},
journal = {Nature Geoscience},
year = {2026},
month = sep,
doi = {10.1038/s41561-026-02104-z},
url = {https://hal.science/hal-05756838v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Experimental constraints on a long-lived magma layer at the Martian core–mantle boundary
AU - Rémy Pierru
AU - Steeve Gréaux
AU - Serena Dominijanni
AU - Lianjie Man
AU - Yoshio Kono
AU - Sho Kakizawa
AU - Yuji Higo
AU - James Badro
AU - Daniel J Frost
AU - Daniele Antonangeli
PY - 2026
DA - 2026/09/18
JO - Nature Geoscience
DO - 10.1038/s41561-026-02104-z
UR - https://hal.science/hal-05756838v1
AB - Geophysical observations from the InSight mission suggest anomalously low seismic velocities near the Martian core–mantle boundary, possibly indicating a molten silicate layer. Such a layer would have major implications for the thermal and chemical evolution of Mars, but its origin remains poorly constrained because experimental data on iron-rich Martian melts at deep-mantle conditions remain scarce. Here we use in situ ultrasonic interferometry combined with X-ray imaging and diffraction to determine the melting phase relations, ultrasonic response and chemical compositions of co-existing melts and solids under conditions relevant to the Martian core–mantle boundary. Our experiments constrain a Martian mantle solidus about 100 K lower than previous estimates. We show that incipient melting rapidly weakens the elastic response, reducing wave speeds and modifying the ultrasonic signal character. Melts generated slightly above the solidus at 18–19 GPa, equivalent to a depth of approximately 1,550 km, are strongly enriched in iron (Fe# of 0.5) and reach densities comparable to or greater than surrounding solids, implying neutral to negative buoyancy. The combination of high melt density and low wetting angles favours the formation of an interconnected dense melt layer near the core–mantle boundary from a moderately FeO-rich Martian mantle without necessarily requiring overturn of an extremely Fe-enriched primordial reservoir and remains compatible with proposed thermal models.
SN - 1752-0894
SN - 1752-0908
ER -