Tidal Evolution of the Moon from a High-Obliquity High-Angular-Momentum Earth

Matija Cuk (SETI)

March 31, 2016

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Abstract: The prevailing giant impact theory fails to explain the Earth-like isotopic composition and substantial orbital inclination of the Moon. If the Moon accreted from a circum-terrestrial disk, a subsequent dynamical process is required to generate the current lunar inclination of 5 degrees. I will show that tidal dissipation due to lunar obliquity was an important effect and the past lunar inclination must have been very large, defying theoretical explanations. I will present a tidal evolution model starting with an initially fast-spinning, high-obliquity Earth. Using numerical modeling, I will show that solar perturbations on the Moon remove angular momentum from the system, while producing an inclined lunar orbit and low-obliquity Earth.