As meteorites from the Moon and Mars continue to be discovered, it is increasingly clear that impact fragments can escape from large bodies more easily than previously believed. These escaping fragments are then subject to the gravitational perturbations of the planets, allowing them to be transferred to a body other than their parent. The lunar meteorites and SNC meteorites prove the plausibility of this process. Warren (1994) summarizes cosmic ray exposure ages and other properties of the lunar and martian meteorites. Their existence confirms that lightly shocked material can be launched at greater than the escape speed of the Moon and Mars.