Impact event such as Engelier and Gerin on Iapetus, Mamaldi on Rhea and Odysseus on Tethys and Herschel on Mimas form significant surface features. 2018 models developed to explain the unusual spin of Uranus support a long-held theory that this was caused by an oblique collision with massive object twice the size of Earth. On July 1994, Comet Shoemaker–Levy 9 was a comet that broke apart and collided with Jupiter, providing the first direct observation of an extraterrestrial collision of Solar System objects. The event served as a "wake-up call", and astronomers responded by starting programs such as Lincoln Near-Earth Asteroid Research
Comet Hale–Bopp and it was visible to the naked eye for twice as long as the previous record-holder. It was also brighter than magnitude 0 for eight weeks, longer than any other recorded comet. Gene Shoemaker and his wife Carolyn, both famous for co-discovering comet Shoemaker–Levy 9, were involved in a car crash after photographing the comet. Gene died in the crash and his ashes were sent to the Moon aboard NASA's "Lunar Prospector" mission along with an image of Hale–Bopp, "the last comet that the Shoemakers observed together". Comet Hale–Bopp Comet Hale–Bopp (formally designated C/1995 O1) is a comet that was