Abstract
Core formation on the Earth and Mars involved the physical separation of metal and silicate, most probably in deep magma oceans1,2,3,4. Although core-formation models explain many aspects of mantle geochemistry, they have not accounted for the large differences observed between the compositions of the mantles of the Earth (∼8?wt% FeO) and Mars (∼18?wt% FeO) or the smaller mass fraction of the martian core5,6,7. Here we explain these differences as a consequence of the solubility of oxygen in liquid iron-alloy increasing with increasing temperature. We assume that the Earth and Mars both accreted from oxidized chondritic material. In a terrestrial magma ocean, 1,200–2,000?km deep, high temperatures resulted in the extraction of FeO from the silicate magma ocean owing to high solubility of oxygen in the metal. Lower temperatures of a martian magma ocean resulted in little or no extraction of FeO from the mantle, which thus remains FeO-rich. The FeO extracted from the Earth's magma ocean may have contributed to chemical heterogeneities in the lowermost mantle8, a FeO-rich D″ layer9 and the light element budget of the core10,11.
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Acknowledgements
We thank H. Fischer, G. Herrmannsdörfer, D. Krausse and H. Schulze for technical assistance. The German Science Foundation (DFG) supported this research.
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Supplementary information
Supplementary Information 1
Justification for the extrapolation of the experimental data to high temperatures and pressures. (DOC 34 kb)
Supplementary Information 2
Electron microprobe analyses of experimental run products. (DOC 303 kb)
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Rubie, D., Gessmann, C. & Frost, D. Partitioning of oxygen during core formation on the Earth and Mars. Nature 429, 58–61 (2004). https://doi.org/10.1038/nature02473
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DOI: https://doi.org/10.1038/nature02473
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