A crater is a large, deep bowl-shaped depression in the ground caused by an impact. Craters can be found on Earth, the Moon, other planets and their moons, and asteroids. They range in size from a few meters across to several kilometers. The largest known crater is Olympus Mons on Mars, which is about 25 kilometers wide.
The most common cause of craters is meteorites striking the surface of a planet or moon. When a meteorite collides with a planet or moon, it releases a tremendous amount of energy. This energy excavates a bowl-shaped depression in the ground called a crater. The size of the crater depends on the size of the meteorite and the type of material it hit. For example, iron meteorites tend to create smaller craters than stony meteorites because they are more dense and thus release less energy upon impact.
Other causes of craters include volcanic eruptions, landslides, and human activity such as mining and quarrying. Craters can also form when glaciers melt and leave behind depressions in the ground (known as glacial cirques).