Well, in multiple body systems there can be normalizing forces from perturbations and inhomogeneous bodies that act to alter orbits- sometimes altering eccentricity, sometimes altering inclination. But these are often weak and slow acting. Many minor moons orbit Saturn and Jupiter at high inclinations- presumably because they were captured. The major moons likely formed in place or were captured very early in the evolution of the Solar System. Nearly all the Solar System mass lies on the ecliptic (really, the invariable plane, but close enough for our discussion), and that's where we find most large bodies orbiting.Rules For wrote:I don't know, other than that nearly all of the other major moons in the Solar System orbit very near to their planet's equatorial plane.Chris Peterson wrote: Well, why should it be on the equatorial plane? Satellite orbits are stable at any inclination.
The Moon is a complex example, given that it likely resulted from a massive collision which would have produced debris at a range of random inclinations, because of the complexity of the Sun-Earth-Moon tidal forces, and because of the way angular momentum is transferred between rotations and orbits.