COG3 Seminar - Junjie Dong (Harvard)

Friday, October 28, 2022 at 10:00am to 11:00am

Building 54, Room 915
21 AMES ST, Cambridge, MA 02139

Water and Phase Transitions in Rocky Planet Interiors

This talk explores two central aspects of rocky planetary interiors—water (Part I) and phase transitions (Part II), with the use of high-pressure experimentation, advanced thermodynamic methods, and statistical and machine-learning algorithms. In Part I, I present a thermodynamic model for the water storage capacity of the solid mantles of Earth and Mars and apply it to explore the two planets’ deep water cycling and surface water stability. Their mantle water capacity generally increases as temperature decreases with secular cooling. Specifically for Earth, the water capacity in a hot, early mantle is likely smaller than the water content in its present-day mantle. Hence, the additional water in the Earth’s mantle today would have resided on its early surface and formed a water world with little exposed land. I further explore the relationship of an early global ocean with geological records and the habitats of early life. In Part II, I introduce a machine-learning approach for determining high-pressure phase transitions from experimental and numerical data, with the focus on its application to Mg2SiO4. This novel approach resolves the nonlinearity of its post-spinel transition. I discuss the effects of this nonlinear transition on mantle convection and its expression in slabs and plumes worldwide: in the present-day mantle, the average post-spinel Clapeyron slope in plumes is about three times more negative than that in slabs.


About this series: The Chemical Oceanography, Geology, Geochemistry, and Geobiology Seminar [COG3] is a student-run seminar series. Topics include chemical oceanography, geology, geochemistry, and geobiology. Contact for more information and Zoom password.


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Department of Earth, Atmospheric and Planetary Sciences
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