Over the Earth’s 4.6 billion years long history, many asteroids and meteorites collided with the Earth. This constant rain of cosmic debris is what made the Earth. In its early days, our planet grew steadily by collecting large and small particles.

Even now, 1 to 10 million kg of cosmic dust rains down each day from space. Why then do we find so few traces of impacts on Earth?

If a meteorite hits the surface of the Earth it makes a big hole, an impact crater. Remarkably, only 171 impact craters have been recognized on Earth, ranging in diameter from 15 metres to a few hundred km.

The larger impact craters usually are the oldest. The biggest one, the Vredefort Crater in South Africa (300 km) was made more than 2 billion years ago.

Only 20 years ago, the third largest impact was found in Mexico, buried beneath 100’s of metres of sediment. It is the Chicxulub crater, measuring 170 km across. It formed when an asteroid, maybe 10 km wide, hit the coast of Yucatan 65 million years ago. It was the asteroid that did in the dinosaurs. We will investigate this event in an article in the next issue of Copernicus.

The biggest impact crater in Europe is Nördlinger Ries in Germany, measuring 24 km across. That one is 15 million years old. There may be an impact crater near you . Find out where and pay a visit.

How dangerous are impacts? Read more: