Delivery of Meteorites to the Earth

Orbits have been calculated for dozens of meteorite falls; they match those of many Near-Earth Asteroids. The Kirkwood Gaps are hiatuses in histograms of asteroid semi-major axes; few asteroids occur in these gaps. The gaps are caused by repeated gravitational tugs by Jupiter on asteroids with orbital periods that are simple fractions of Jupiter’s orbital period. Among the most efficient mechanisms for delivering asteroids to the Earth is the υ 6 resonance associated with Saturn. The resonance occurs when there is a simple numerical ratio between the precession frequency of an asteroid’s longitude of perihelion and that of the mean precession frequency of Saturn’s longitude of perihelion.