An integral approach to reveal the identity of light elements in the Earth's core

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The Earth has an iron-dominant core that consists of a liquid outer core and a solid inner core at the center. The Earth's core is the engine of the planet, generating global magnetic field and driving large-scale plate motions on the surface through mantle convection. A better understanding of its chemical composition will help us to understand how the engine works. Current knowledge of the core implies that incorporation of light elements (such as sulfur, oxygen, silicon) in the iron core is necessary to explain the observed density and velocities of the core, but there is considerable controversy over the precise identity of the light alloying elements in the core because it is experimentally challenging to precisely measure the density and sound velocity of the iron alloys under core conditions.In this study, I am outlining a new approach to narrow down the identity of the light elements in the core by combining dynamic and static compression experiments. The proposed experiments will yield new density and velocity data obtained by shock compression and static compression in the high-temperature diamond-anvil cell. Specifically, I propose four types of experiments, (1) shock compression to obtain densities of Fe-Si alloys, (2) in-situ x-ray diffraction measurements in high-temperature diamond-anvil cell to obtain P-V-T data, (3) measurements of the sound velocities of the alloys by shockwave experiments, and (4) measurements of the compressional-wave velocity of alloys in the high-temperature diamond-anvil cell by inelastic x-ray scattering technique. This is our first attempt to integrate results from dynamic and static compression experiments on the same samples, which allows us to obtain complementary data over a wide P-T range and to establish self-consistent database from two independent high-pressure experiments. The new data on Fe-Si alloys will be integrated into our existing data to make comprehensive models of the core.