An impact event is a collision between celestial objects causing measurable effects. Impact events have physical consequences and have been found to regularly occur, though typically relatively small and involving asteroids, comets or meteoroids. When terrestrial planets such as Earth are involved in large impact events, there can be physical and biospheric consequences, though atmospheric entry mitigates most surface impacts. Impact events have played a significant role in the evolution of the Solar System since the beginning and in the origins and evolution of the Earth. Major impact events have significantly shaped Earth’s history, have been implicated in the formation of the Earth–Moon system, the evolutionary history of life, the origin of water on Earth and several mass extinctions. Impact craters are the result of impact events on solid objects and as the dominant landforms on many of the System’s solid objects and provide the most solid evidence of prehistoric events. Notable impact events include the Late Heavy Bombardment, which occurred early in history of the Earth–Moon system and the Chicxulub impact, 65 million years ago, believed to be the cause of the Cretaceous–Paleogene extinction event.
