The Earth’s core as a reservoir of water

Using ab initio molecular dynamics and thermodynamic integration techniques, two TYC members were part of a team who conducted calculations to show that water prefers to be in liquid iron rather than silicate melt, concluding that the Earth’s core may host most of the planet’s water inventory.  The paper was published in Nature Geoscience Volume 13 and corresponding image used for the cover.

Current estimates of the budget and distribution of water in the Earth have large uncertainties, most of which are due to the lack of information about the deep Earth. Recent studies suggest that the Earth could have gained a considerable amount of water during the early stages of its evolution from the hydrogen-rich solar nebula, and that a large amount of the water in the Earth may have partitioned into the core. Here we calculate the partitioning of water between iron and silicate melts at 20–135 GPa and 2,800–5,000 K, using ab initio molecular dynamics and thermodynamic integration techniques. Our results show that water always partitions strongly into the iron liquid under core-formation conditions. We therefore conclude that the Earth’s core may act as a large reservoir that contains most of the Earth’s water.

Nature Geoscience Volume 13

  • Hydrogen exhibits siderophile behaviour, preferring to enter liquid iron rather than the silicate melt under core-mantle differentiation and core-mantle boundary conditions. The image shows the trajectories of hydrogen atoms in the equilibrated iron and silicate melts, with more in the iron region (the lower part) and less in the silicate region (the upper part).

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