Physics and Chemistry of Planetary Materials at Extreme Conditions

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The objective of my research is to improve our abilities to understand the deep interior dynamics and evolution of Earth and other planets. The dynamics and evolution of Earth’s and planetary interiors will influence the outermost features of the Earth and other planets. However, Earth’s and planetary interiors are inaccessible and cannot be directly investigated. Alternative approaches are to study Earth and planetary materials at simulated environments that are similar to Earth and planetary interiors. In addition, behavior of materials at ambient conditions (1 atm and 25 C) is different from what they exhibit at greater depths. Therefore, only those data collected at pressure and temperature conditions corresponding to the certain depths are valid for modeling the structure and dynamics of the Earth’s and planetary interiors. Therefore, study of Earth and planetary materials at pressure and temperature conditions corresponding to their deep interiors provide promising approach to understand the dynamics and evolution of Earth’s and planetary interiors. My research program uses high pressure apparatus, a diamond-anvil cell (DAC, able to generate pressure from 1 to 3,000,000 atm) together with resistive and laser heating methods (able to heat the sample to 3000 - 4000 K), to study planetary materials under extreme pressure and temperature conditions. The extensive pressure and temperature ranges (1 - 3,000,000 atm and 300 - 4000 K) allow us to replicate the conditions found within the Earth and planetary interiors. Moreover, using a custom-built micro-Raman system and synchrotron infrared spectroscopy, the spectroscopic properties of relevant materials are also examined. In this proposal, we synthesize the important deep mantle phases (e.g. aluminum and iron-rich perovskite and post-perovskite, carbon- and hydrogen-bearing silicates, spinels, oxides and iron alloys) and characterize them using synchrotron x-ray diffraction, x-ray spectroscopy, Raman and infrared to understand their structures and physical properties (e.g. density, volume, elasticity, strength, stress). The synthesized samples when quenched to ambient conditions will be examined by electron probe microanalysis (EPMA), scanning electron microscopy (SEM) and analytical transmitting electron microscopy (ATEM) for understanding the partitioning of the elements and element distributions within the samples, the melting criteria of the iron alloy, and the crystal structures of the nano-scale phases. Our goals are (1) to understand the causes and mechanism of seismic anomalies (e.g. ultralow velocity) found within the D” layer, (2) to build a strength model of mixed mantle phases that can be applied to modeling the dynamics of the Earth’s interior, (3) to evaluate the high pressure polymorphs of chromium spinel at high pressure-temperature conditions as well as its connection to the shocked meteorites, and (4) to evaluate the budgets of the hydrogen and carbon inside the Earth via the carbon- and hydrogen-bearing deep mantle phases. The proposed projects will promote interdisciplinary work and education in the fields of mineral physics, geodynamics, planetary science and material science. In addition, HQP will receive well-rounded training in the high pressure research. They will use powerful analytical tools at UWO and state-of-the-art synchrotron facilities at different locations for their projects. Especially, HQP will greatly benefit from their participations in the synchrotron trips as they will have excellent opportunities to expose themselves to different fields of communities. This will be of great help for their future careers.