Impact event

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Artist's impression of a major impact event. The collision between a planet and an asteroid a few kilometers in diameter may release as much energy as several million nuclear weapons detonating simultaneously.

 

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.
Throughout recorded history, hundreds of Earth impacts (and exploding bolides) have been reported, with some occurrences causing deaths, injuries, property damage or other significant localised consequences.^[1] One of the best-known recorded impacts in modern times was the Tunguska event, which occurred in Siberia, Russia, in 1908. The 2013 Chelyabinsk meteor event is the only known such event to result in a large number of casualties, and the Chelyabinsk meteor is the largest recorded object to have encountered the Earth since the Tunguska event. The most notable non-terrestrial event is the Comet Shoemaker–Levy 9 impact, which provided the first direct observation of an extraterrestrial collision of Solar System objects, when the comet broke apart and collided with Jupiter in July 1994. Impact events have been a plot and background element in science fiction since knowledge of real impacts became established in the scientific mainstream.