Impact event facts for kids
An impact event is a collision between objects in space. They happen regularly in planetary systems, such as our Solar System. They most often involve small objects, such as asteroids, comets or meteors. 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 impact prediction. Depending on the size of the object, much of the impact is reduced by the planet's atmosphere. Smaller objects explode or break apart as they enter the atmosphere. These are seen as bolides.
Impact craters, 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, Shoemaker–Levy 9, broke apart and collided with Jupiter. The collision was recorded by telescopes and satellites.
Impact events appear to have had a major effect on the how the Solar System has changed since it was formed. Major impact events have also shaped the history of the Earth, including the evolution of life. It is thought that the Chicxulub impact, which happened 66 million years ago, caused the Cretaceous–Paleogene extinction event. There is debate over whether impacts caused any of the other extinction events throughout history. A giant impact event is thought to have produced the Moon.
Hundreds of impacts have been reported on Earth. Many happen without being seen by anyone on the ground. On average, asteroids with a diameter of 4 meters (13 ft) impact Earth about once per year. These usually explode in the upper atmosphere, and most or all of the solids are vaporised. Asteroids with a diameter of 1 km (0.62 mi) collide with Earth every 500,000 years. Large collisions, of 5 km (3 mi), happen once every twenty million years. Some much smaller asteroids have caused damage and injuries, but no human is known to have been killed directly by an impact. The Chelyabinsk meteor event in 2013 is the only impact event known to have resulted in a large number of injuries. It was about 20 metres wide. One of the most well-known impacts in modern times was the Tunguska event. This happened in Siberia in 1908. Impacts of that size are said to happen about once every thousand years.
Related pages
Images for kids
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A bolide undergoing atmospheric entry
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Eugene Merle Shoemaker was first to prove that meteorite impacts have affected the Earth.
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An animation modelling the impact, and subsequent crater formation of the Chicxulub impact (University of Arizona, Space Imagery Center)
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Aerial view of Barringer Crater in Arizona
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Trees knocked over by the Tunguska blast
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Trail left by the exploding Chelyabinsk meteor as it passed over the city.
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Orbit and positions of 2018 LA and Earth, 30 days before impact. The diagram illustrates how orbit data can be used to predict impacts well in advance. Note that in this particular instance the asteroid's orbit was not known until a few hours before impact. The diagram was constructed afterwards for illustration.
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Topographical map of the South Pole–Aitken basin based on Kaguya data provides evidence of a massive impact event on the Moon some 4.3 billion years ago
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Comet Shoemaker-Levy 9's scar on Jupiter (dark area near Jupiter's limb)
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Hubble's Wide Field Camera 3 clearly shows the slow evolution of the debris coming from asteroid P/2010 A2, assumed to be due to a collision with a smaller asteroid.
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Asteroid collision led to the building of planets near star NGC 2547-ID8 (artist concept).
See also
In Spanish: Impacto astronómico para niños
