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Thermodynamics of Fe-S-O-C-H liquids: Implications for the Martian core

van Driel, Jac; Vočadlo, Lidunka; Brodholt, John; (2025) Thermodynamics of Fe-S-O-C-H liquids: Implications for the Martian core. Earth and Planetary Science Letters , 668 , Article 119540. 10.1016/j.epsl.2025.119540. (In press). Green open access

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Abstract

We present a comprehensive investigation into the composition of the Martian core. We use new density functional theory (DFT) calculations, which consider in detail the magnetic properties of the Fe alloys, essential for obtaining the correct density and velocities. We then fit our results to a new Gaussian Process Regression (GPR) equation of state (EOS). Using this GPR-EOS we search for all compositions of the Martian core in the system Fe-S-O-CH that match both the density and compressional wave speeds of a liquid Martian core throughout its entire depth range. We consider different models for the interior of Mars -- in particular, those with and without a deep melt layer at the base of the Martian mantle (Irving et al., 2023; Samuel et al., 2023; Khan et al., 2023). The existence of a deep melt layer is important as it revises previous estimates for the core’s size and density. We consider a range of core-mantle boundary temperatures from 1900 K to 2850 K, although we find that temperature has a relatively small effect on the possible compositions. As with previous studies, and also for the Earth, we find many different compositions that are able to match the geophysical observations of Mars’ core density (

Type: Article
Title: Thermodynamics of Fe-S-O-C-H liquids: Implications for the Martian core
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.epsl.2025.119540
Publisher version: https://doi.org/10.1016/j.epsl.2025.119540
Language: English
Additional information: Crown Copyright © 2025 Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Keywords: Martian core, Magnetism, Iron alloys
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/10211561
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