College of Science

SEMINAR: The origin of the Moon within a terrestrial synestia, Dr. Simon Lock [Caltech]

SEMINAR: The origin of the Moon within a terrestrial synestia, Dr. Simon Lock [Caltech]

Nov 14, 2019 11:00 AM to Nov 14, 2019 12:00 PM at 8-241

Physics and Astronomy Seminar

November 14, 2019, 11:00 am to 12:00 pm at Building 8, Room 241

 

Dr. Simon Lock (Caltech)

 

The origin of the Moon within a terrestrial synestia


The giant impact hypothesis has been the leading theory for the origin of the Moon for decades, but current models struggle to explain the Moon's composition and isotopic similarity with Earth. I will present a new lunar origin model based on the discovery that high‐energy, high‐angular‐momentum giant impacts can create a previously unrecognized type of planetary structure, named a synestia. Using simulations of cooling synestias combined with dynamic, thermodynamic, and geochemical calculations, I will show that satellite formation from a synestia can produce the principal features of our Moon. Cooling of the synestia drives condensation, producing moonlets that orbit within the synestia, surrounded by tens of bars of bulk silicate Earth vapor. Moonlets equilibrate with bulk silicate Earth vapor at the temperature of silicate vaporization and the pressure of the structure, establishing the lunar isotopic and chemical composition. Eventually, the cooling synestia recedes within the lunar orbit, terminating the main stage of lunar accretion. Our model shifts the paradigm for lunar origin from specifying a certain impact scenario to achieving a Moon‐forming synestia.

 

10:50 am Refreshments

 

11:00 am Seminar