Secular chaos in the solar system
Motivated by Laskar's 2008 finding that secular interactions among the eight major solar system planets 1) cause the four inner planets to act chaotically and 2) induce much larger eccentricity/inclination variations for Mercury than for Venus, Earth, or Mars, we investigate higher-order couplings between the normal modes of the classical Laplace-Lagrange secular theory. We do this by constructing, in effect, a secular theory for these normal modes; we include long-term effects of near two-body mean-motion resonances among the outer planets. We study the effects on both the giant planets and on test particles (e.g. asteroids/Kuiper belt objects) of the resulting weak nonlinear couplings between the normal modes dominating inner- and outer-planet motions.