Hydrogen is the most abundant element in the universe, making it one of the most plausible light element of the Earth's core. However, by compiling the existing data we found that the hydrogen content of the Earth's core vary from about 50 ppm to about 1 wt%. Such differences have important implications not only on the physical and chemical properties of the Earth's core, but also on the sources of planetary volatiles and the timing at which they were accreted to growing planets. Here we present new experiments simulating the earliest conditions of planet accretion by performing molten metal – silicate liquid partitioning experiments between 1 and 20 GPa, and use them to determine an accurate picture of the behaviour of hydrogen during terrestrial core formation. The originality of our approach is to use concentrations of volatile elements (C, H, and S) that are close to those supposed to be during the accretion of terrestrial planets. The results show that the metal-silicate partition coefficients of hydrogen are < 1 for pressures < 5 GPa, consistent with the experimental studies at similar conditions (e.g. Clesi et al., 2018; Malavergne et al., 2019). These coefficients are mainly dependent on the chemical composition of the metallic phase. The final stages of Earth's core formation that involve high pressures and high temperatures conditions, hydrogen seems to be siderophile with DH > 20 (e.g. Tagawa et al., 2021). In this presentation we will discuss our new results and determine the plausible range of hydrogen contents of the core of the Earth and Mars by taking into account all parameters that affect the metal-silicate partitioning of hydrogen: P, T, and especially the interactions of the major light elements of the core with hydrogen (C, Si, S and O).
| Subject : | : | Oral |
| Topics | : | Earth's Mantle and Core |
| Topics | : | Keynote |
| Keywords | : | Hydrogen | Terrestrial planets | Accretion | Differentiation | Volatiles |
| PDF version | : |  PDF version |
