About 66 million years ago, an asteroid crashed into Earth. It was massive, 10 to 15 kilometres wide. It hit Mexico so hard that it left a crater 150 kilometres across and 20 kilometres deep. 

The event wiped out 75 percent of life on Earth, including the dinosaurs.

Boom!

Even smaller asteroids are dangerous. In 2013, a 20-metre asteroid blew up over Chelyabinsk, Russia. The blast hurt 1500 people and damaged 7200 buildings.