The Earth-Moon System and the Dynamical Stability of the Inner Solar System

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Abstract
Evidence from self-consistent solar system n-body simulations is presented to argue that the Earth-Moon system (EM) plays an important dynamical role in the inner solar system, stabilizing the orbits of Venus and Mercury by suppressing a strong secular resonance of period 8.1 Myr near Venus's heliocentric distance. The EM thus appears to play a kind of "gravitational keystone" role in the terrestrial precinct, for without it, the orbits of Venus and Mercury become immediately destabilized. The mechanism of the resonance, driven by the giant planets, is described. Approximate limits are provided for the mass and heliocentric distance required of EM to perform this role, and results from several additional empirical tests are reported. A number of avenues of further investigation are suggested.