Loss of a satellite could explain Saturn's obliquity and young rings.

The origin of Saturn's ~26.7° obliquity and ~100-million-year-old rings is unknown. The observed rapid outward migration of Saturn's largest satellite, Titan, could have raised Saturn's obliquity through a spin-orbit precession resonance with Neptune.

Vertical angular momentum constraint on lunar formation and orbital history.

The Moon likely formed in a giant impact that left behind a fast-rotating Earth, but the details are still uncertain. Here, we examine the implications of a constraint that has not been fully exploited: The component of the Earth-Moon system's angular momentum that is perpendicular to the Earth's orbital plane is nearly conserved in Earth-Moon history, except for possible intervals when the lunar orbit is in resonance with the Earth's motion about the Sun. This condition sharply constrains the postimpact Earth orientation and the subsequent lunar orbital history.

Evidence for a past high-eccentricity lunar orbit.

The large differences between the Moon's three principal moments of inertia have been a mystery since Laplace considered them in 1799. Here we present calculations that show how past high-eccentricity orbits can account for the moment differences, represented by the low-order lunar gravity field and libration parameters. One of our solutions is that the Moon may have once been in a 3:2 resonance of orbit period to spin period, similar to Mercury's present state.

Swimming in spacetime: motion by cyclic changes in body shape.

Cyclic changes in the shape of a quasi-rigid body on a curved manifold can lead to net translation and/or rotation of the body. The amount of translation depends on the intrinsic curvature of the manifold. Presuming spacetime is a curved manifold as portrayed by general relativity, translation in space can be accomplished simply by cyclic changes in the shape of a body, without any external forces.