2023-2024: Mineral and Rock Physics: Thomas Duffy

Thomas Duffy
Princeton University


Thomas Duffy has been a professor in the Department of Geosciences at Princeton University since 1997. His research interests broadly focus on mineralogy and mineral physics with an emphasis on the properties of  geological materials at high pressures with applications to understanding the structure and dynamics of the Earth and other planets. Specific areas of research include the mineralogy of the Earth’s upper and lower mantles, shock compression of geological materials,  and the use of novel laser compression techniques to achieve ultrahigh pressures relevant to the interiors of large exoplanets. His work explores crystal structures, equations of state, phase transitions, and elastic properties of all types of Earth and planetary materials.

Thomas received his Ph.D. from the California Institute of Technology in 1992.  He joined Princeton after postdoctoral and research scientist positions at the Carnegie Institution for Science and the University of Chicago. He is currently Chair of the Geosciences Department at Princeton, an affiliated faculty at the Princeton Materials Institute, and a member of the Academic Freedom Alliance.  Recently, he led an effort to develop a national plan for  the management and operation of synchrotron-hosted analytical capabilities for Earth sciences research. He is a fellow of the American Geophysical Union, the Mineralogical Society of America, and the David and Lucile Packard Foundation.

Abstract: Journey to the Center of a Super-Earth

The discovery of thousands of extra-solar planets orbiting other stars in our galaxy is one of the most remarkable scientific findings in recent decades. The largest number of observed extra-solar planets fall in the size range between Earth and Neptune, and hence have no direct analogs in our solar system. Based on their measured masses and radii, many of these planets have Earth-like (i.e. rock and metal) compositions but can be much larger -- up to ten Earth masses in size. The discovery of these “super-Earths” raises fundamental questions about how their internal mineralogy, structure, and dynamics may be distinct from that of Earth and other terrestrial planets in our solar system. One major difference between Earth and super-Earths are the internal pressures which may reach an order of magnitude larger values in super-Earths compared with Earth’s interior. These ultra-high pressures can greatly alter the crystal structures and hence physical and chemical properties of the minerals of the deep interior of super-Earths, leading to potentially highly novel planetary behavior. This talk will (1) summarize observations of rocky super-Earths, (2) describe newly developed experimental techniques for determining how minerals respond to the extreme pressures of super-Earth interiors, and (3) explore how the novel mineralogy of super-Earths may influence their large-scale interior structure, their thermal evolution, and even the surface features of these bodies.