Impact crater
A hole blasted in the surface of a planet, moon or asteroid when a fast-moving object from space crashes into it.
An impact crater forms when a lump of rock or metal from space hits a solid surface at enormous speed, often tens of kilometres every second. It does not simply dig a hole like a spade. The crash releases so much energy, so quickly, that it acts like a giant explosion, throwing rock outwards in every direction. That is why craters are round, even when the object came in at a slant.
The Moon is covered in craters you can see with binoculars, because it has no wind, rain or plants to wipe them away. Earth has been hit many times too, but most of its craters have been worn down, buried or swallowed by moving rock over millions of years. Scientists have confirmed around 200 of them so far.
One of the best preserved is Barringer Crater, also called Meteor Crater, in Arizona, USA. It is about 1.2 kilometres across and formed about 50,000 years ago when an iron meteorite struck. Thousands of pieces of that iron, called Canyon Diablo, have been found around it. Signs that a round hole is an impact crater include a raised rim, broken and shocked rocks, and sometimes pieces of meteorite nearby.
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Level: Beginner Ages 7 and up