Asteroid deflection. Artwork of a mass driver robot on a near-Earth asteroid. The robot drills into the asteroid and electromagnetically catapults material into space. The force created by the device, and the decreasing mass of the asteroid, gently nudges it away from an Earth- bound orbit. Asteroids are minor planets with diameters of less than 100 kilometres. A collision with Earth would cause massive tsunamis if it hit the oceans and block sunlight due to the huge quantities of dust thrown in to the stratosphere. It is thought that the extinction of the dinosaurs around 65 million years ago was caused by an asteroid impact. An asteroid, comet or other large body posing a danger to Earth is known as a Near- Earth Object (NEO).