PICS Seminar: Chuan Qin (Harvard)

Chuan Qin (Harvard)
Tuesday, April 16, 2019 - 12:30pm to 1:30pm

Formation of Moon's fossil bulge and its implication for Earth's early conditions

First recognized by Laplace over two centuries ago, the lunar gravitational anomalies associated with tidal-rotational bulges are significantly larger than hydrostatic values. They are likely relics of a former hydrostatic state when the Moon was closer to the Earth and had larger bulges, and they were established when stresses in a thickening lunar lithosphere could maintain the bulges against hydrostatic adjustment. We formulate the first dynamically consistent model of this process and show that bulge formation is controlled by the relative timing of lithosphere thickening and lunar orbit recession. Our models indicate that lunar fossil bulge formation was a geologically slow process lasting several hundred Myr, and was complete about 4 Ga when the Earth-Moon distance was less than ~32 Earth radii. The models demonstrate that the early Earth was significantly less dissipative to lunar tides than during the last 4 Gyr, suggesting a frozen Earth’s hydrosphere due to the faint young Sun and limited greenhouse effects in the Hadean eon prior to 4 Ga.

Bio: Chuan Qin is a Postdoctoral Fellow at Harvard University working in the fields of geophysics and planetary science. He develops physical models to understand the interior dynamics of the Earth and other planets at different time scales. Qin's interested include analyzing large remote sensing and gravity field datasets, developing new analytical methods to calculate gravity fields and topography of planets from their interior dynamics, and developing numerical code for 3-D large scale simulations of thermo-hydrodynamic processes in planets.

About the Series

The MIT Planetary Lunch Colloquium Series [PlCS] is a weekly seminar series organized within the EAPS department. Colloquia topics span the range of research interests of the department's planetary sciences research program. The seminars usually take place on Tuesdays from 12:30-1:30 pm in 54-1623 unless otherwise noted (term-time only). Speakers include members of the MIT community and visitors. Talks are intended to appeal to graduate students, postdocs, research scientists, and faculty with a background in planetary science. A light lunch is provided.