Scientists say comets have caused the strange ripples observed in the ring systems of Saturn and Jupiter. The ripples in Jupiter's rings are believed to have been caused by the comet Shoemaker-Levy 9, which struck the planet in 1994. The findings suggest that the subtle corrugations seen in Saturn's rings, as well as the ripples detected in Jupiter's rings, can provide a record of the directions of comets, coming and going, after the time of impact of the atmosphere. Dr. Mark Showalter at California's SETI Institute