What is Impact event?
[[File:Impact event.jpg|thumb|250px|Illustration of a large [[asteroid]] entering Earth's atmosphere]] [[File:Artist's concept of collision at HD 172555.jpg|thumb|250px|Illustration of an object about the size of the Moon, colliding into a planet]] An '''impact event''' is a [[collision]] between [[Astronomical object|objects]] in [[Outer space|space]]. They happen regularly in [[planetary system]]s, such as our [[Solar System]]. They most often involve small objects, such as [[asteroid]]s, [[comet]]s or [[meteor]]s. These have relatively little impact. When a large object collides with a [[planet]] like the [[Earth]], it can have serious effects on the planet. We try to find out when one is going to hit Earth using [[Asteroid impact prediction|impact prediction]]. Depending on the size of the object, much of the impact is reduced by the planet's [[atmosphere]]. Smaller objects [[Explosion|explode]] or break apart as they enter the atmosphere. These are seen as [[bolide]]s. [[Impact crater]]s, which are caused by impact events, can be seen on many of the planets and other objects in the Solar System. Some of the largest are on [[Mars]] and the [[Moon]]. These are said to be evidence of major impact events. The first time an impact event was recorded was in July 1994. A [[comet]], [[Comet Shoemaker–Levy 9|Shoemaker–Levy 9]], broke apart and collided with [[Jupiter]].<ref name=NASA2005>{{cite web|url=http://nssdc.gsfc.nasa.gov/planetary/comet.html |title=Comet Shoemaker–Levy 9 Collision with Jupiter |accessdate=2008-08-26 |publisher=[[National Space Science Data Center]] |date=February 2005}}</ref> The collision was recorded by [[telescope]]s and [[satellite]]s.<ref>{{cite web |url=http://nssdc.gsfc.nasa.gov/planetary/others.html |last=Williams|first=David R.|title=Ulysses and Voyager 2 |accessdate=August 25, 2008 |work=Lunar and Planetary Science |publisher=[[National Space Science Data Center]]}}</ref> Impact events appear to have had a major effect on the [[Formation and evolution of the Solar System|how the S