Story highlights Asteroids may be small compared to size of the Earth but they can cause massive destruction owing to their very high speeds It may be just another day for us here on Earth. We may get up and go about as if nothing is going to happen. But ask those Dinosaurs who were out on the day an asteroid struck Earth. Well, you can't of course because all of them are dead (along with around 75 per cent of life at that time on the planet). This is what happens when a huge space rock decides that it is tired of travelling through space and wants to 'settle down' on the cosy planet we call Earth.