Geophysics of Iron in the Earth's Core

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Analyzing the seismic waves that pass through our planet have provide observations of its internal structure including, the Earth's core which is composed of a liquid iron-rich outer region which lies above the solid, iron-rich inner core. In order to understand the constituents that make up this most remote region in our planet, we propose to conduct the challenging laboratory experiments at the high pressures and temperatures that exist in the Earth?s deep interior, and to measure of the properties of iron-rich materials which can be dramatically altered under the extreme conditions. The primary goal of the present research is thus to understand the Earth's core which plays a central role in the evolution, magnetism, dynamic processes, and thermal evolution of our planet. Building upon our progress resulting from our prior support, this project takes a two-pronged approach: using static high-pressure techniques in a diamond anvil cell for accurate determination of elastic properties and dynamic compression created by powerful lasers for ultrahigh pressure-temperature sound velocity measurements. For the static high-pressure experiments, we propose to determine the equation of state, aggregate compressional and shear wave velocities, velocity anisotropy and lattice preferred orientation, and elastic tensor of iron using a suite of complementary synchrotron x-ray techniques. For the dynamic experiments, we will collaborate with the Shock Physics Group at Lawrence Livermore National Laboratory and use the Janus laser facility to determine the compressional and especially the shear wave velocities (using a transverse displacement interferometer set-up) for iron and iron alloys. The combination of the static and dynamic results will provide important information for helping to understand and interpret the complex seismic signatures in the Earth's core. The anticipated, high pressure-temperature elasticity data for iron will be valuable to a wide variety of researchers involved in deep Earth studies (e.g. theoretical mineral physicists for improving their calculations, seismologists for interpretation of their observations, and geodynamicists for constraining their models). In addition, the technical advances will be useful to other experimentalists in the geosciences as well as fundamental and applied sciences.