ABSTRACT

Residing at the center of the Earth, the core is the innermost but extremely dynamic region of our planet. Over the last two decades, geophysicists have expended tremendous effort in deciphering the compositional makeup, thermal structure, and seismic features of the Earth's core. Understanding the nature and dynamics of the core can deeply enhance our abilities in understanding the magnetic field generation process, the thermo-chemical evolution of the Earth's deep interior, and the formation of the Earth as a habitable planet. This Faculty Early Career Development (CAREER) program aims to investigate the elasticity and lattice dynamics of iron alloys as candidates for the inner core under high pressure and temperature conditions of the core, using multiscale state-of-the-art experimental facilities. The outcome of the proposed research is a new set of fundamental mineral physics data on density, sound velocities, and single-crystal elasticity of iron alloys under previously uncharted pressure-temperature regimes, essential for us to provide further constraints on the core's composition and dynamics. The experimental results are to be integrated to a comprehensive mineral physics database for the core, cultivating collaborations with sister disciplines such as seismology, geodynamics and geochemistry, and ultimately enhancing our profound understanding of nature and dynamics of the Earth's deepest interior. Furthermore, the involvement of student researchers in the proposed research and the development of a research and teaching facility for high-pressure mineral and materials science will initiate the 'pipeline' that helps influence and attract diverse student population, particularly traditionally underrepresented minorities, into Earth science and build diverse geoscience workforce.

This proposal aims to systematically measure high pressure-temperature elastic and vibrational properties of candidate iron alloys for the inner core, using synchrotron-based X-ray spectroscopies combined with resistively- and laser-heated diamond anvil cell techniques, so as to address the following scientific questions: (1) How do pressure and temperature affect the elastic and vibrational properties of iron alloys under core conditions? (2) What are the alloying effects of candidate light elements on the elasticity of iron under core conditions? (3) What are the single crystal elasticities of iron alloys approaching the core conditions, for the interpretation of the inner core's seismic anisotropy and fine-scale seismic? (4) Finally, what are the likely lighter alloying components in the inner core and what would that imply for the thermochemical evolution of the core and the planet? The integrated education and outreach objective is to train a new generation of independent solid Earth geoscientists in laboratory- and synchrotron-based facilities and to offer inquiry-base learning opportunities and experience to K-16 students through the implementation of a 'Multi-Anvil Press Laboratory' (MAPLab) teaching module to geosciences curricula. The results of the project will be widely disseminated on a timely manner through national and international meetings, public lectures and outreach, and news media.

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