The Surprising State of the Earth after the Moon-Forming Giant Impact


Tuesday, January 27 2015 - 12:00 pm, PST
Sarah Stewart
UC Davis

In the giant impact hypothesis, the Moon accretes from a disk around the proto-Earth. In the canonical model, the impact also sets the present-day angular momentum (AM). Alternatively, the Moon may form via a high AM giant impact and the present-day AM was established by a lunar orbital resonance. I will discuss the unusual state of the Earth after a high angular momentum impact: a continuous pressure- and rotationally-supported fluid-to-vapor structure from the mantle to the disk. The surface of the structure cools radiatively and forms droplets. The droplets settle to the mid plane beyond the Roche radius and form moonlets. If mixing between the atmosphere and inner disk is efficient, then a wide range of high AM giant impacts may produce the isotopic similarity between the Earth and Moon.

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