What happens when a meteorite hits the ground?
When a large meteorite hits the ground it can produce a crater. Meteorite craters are rare on the Earth, because the atmosphere slows the meteorite and also usually burns it up. Many ancient meteorite craters have been worn away by water and by weather over thousands of years.
On planets and moons with no atmosphere, huge numbers of meteorites strike with enormous power. Our own Moon is estimated to have 3,000,000 million meteorite craters measuring 1 m or more in diameter. Some of the large geographical features on the Moon and other planets and moons throughout the Solar System are probably the result of strikes by large meteors hitting their surfaces.
What are meteorites made of?
Meteorites are made of rock or metal. They enter the Earth’s atmosphere at speeds of at least 11 km per second, which makes them glow brightly. Several thousand meteorites enter the Earth’s atmosphere every year, but very few of them reach the ground. The largest known meteorite is made of iron and weighs 66 tonnes. It probably fell to the Earth in prehistoric times in what is now Namibia, southwest Africa.
In general it is hard to find meteorites. Recently, researchers have been locating them on the ice sheets in the Arctic and Antarctic, where they are easier to find.
Why is Europa especially interesting?
Europa is one of Jupiter’s moons. In 1979 the Voyager spacecraft passed by Europa and found that it had a very smooth surface covered with ice. It has very few craters, which has led astronomers to suspect that there may be liquid water beneath the surface. In theory, there might even be a form of primitive life hidden beneath the ice, where water remains as a liquid.