million years ago and probably played a major role in the extinction of the non-avian dinosaurs. Several other large impact craters of around the same age have been discovered, all between latitudes 20°N and 70°N, leading to the speculative hypothesis that the Chicxulub impact may have been only one of several impacts that happened all at the same time. The collision of Comet Shoemaker-Levy 9 with Jupiter in 1994 proved that gravitational interactions can fragment a comet, giving rise to many impacts over a period of a few days if the comet fragments should collide with a planet. Comets frequently undergo gravitational interactions with the gas giants, and similar disruptions and collisions are very likely to have occurred in the past. While this scenario may have occurred on Earth 66 million years ago, evidence for this hypothesis is not strong. In particular, the ages of some of the possibly related craters are only known to an accuracy of a few million years. Also, the now widely held previously stated belief that Silverpit was not formed by bolide impact reduces the possibility of it being involved in this hypothesis. Even if it were formed by bolide impact, the increased uncertainty in the age estimate for Silverpit to 74–45 million years further weakens the hypothesis. See also BP Structure, an impact crater also discovered by BP. Doggerland, the Silverpit's area which was above sea level in human prehistory Impact event List of possible impact structures on Earth Mjølnir crater, a 145 million years impact crater in the Barents sea. Stac Fada Member (Ullapool bolide), another proposed impact crater in the British Isles References External links UK's first impact crater discovered National Geographic news David Darling's space encyclopedia The Geological Society of London Further information from the Geological Society of London Cretaceous impact craters Extinction events Impact craters of Europe Paleocene impact craters Landforms of the North Sea