This project is a collaborative effort to study the origin of Earth's core and its relationship to the timing and mechanism of planetary accretion. This effort combines experimental and theoretical work and relies on a novel concept of high pressure-temperature chemical studies in diamond cells, on fluid dynamic modeling of multiphase flows and planetary evolution, and on geochemical modeling combining parameters from the experiments and the fluid-dynamic modeling to establish confidence limits on models of core-formation and evolution of an impact-induced magma-ocean. The experimental program will determine the partitioning of a set of key elements near the lithophile-siderophile boundary and certain highly siderophile elements that are involved in important radioactive decay systems. Geochemical signatures of both types of elements in the Earth's mantle provide the record of core-formation, because this process efficiently extracted siderophile elements out of the mantle. Temperature, pressure, and time-scale of this extraction processes are the unknown parameters the proposed combination of experimental, theoretical, and geochemical findings shall constrain. The proposed experiments will focus on partitioning of Hf and W and of Re and Os between liquid silicate and metal using W-, Re-, and Os-rich iron-alloys as internal metal heaters embedded in liquid silicate systems in high-pressure experiments. Varying bulk Fe content in the starting materials provides sets of Fe-normalized partition coefficients (kD-values) for the silicate-metal system which then can be extrapolated from the actual experimental redox conditions (close to the respective metal-oxide buffers) to the more reducing conditions of Earth's core formation and from the highly enriched experimental metal-silicate systems to natural abundances of the examined elements. Along with this experimental effort these researchers will start to incorporate for the first time fundamental advances in understanding emulsification of fluid mixtures into methods of fluid dynamic modeling of impact accretion and planetary differentiation processes.
