Asteroid

One of a number of bodies composed primarily of either rock or iron that can be found mainly in the asteroid belt between Mars and Jupiter. Asteroids range in size from very small to up to over 1000km or more across. It is believed that the Asteroid belt comprises of the materials left over from planetary formation and could have been formed from the remains of a planet that was unable to form due to the disruptive gravitational effects of the planet Jupiter. Combined, the total mass of all the asteroids in the belt add up to less than that of our own moon.

Asteroid impact

Massive asteroids have collided with the Earth throughout its history and have in many cases caused substantial devastation to life on the planet. Extinctions of many prehistoric species have been attributed to such events and both scientists and science fiction have made no secret of the fact that it could happen again at any time with devastating consequences