In this cataclysmic scene, a city is hit by a hail of meteorites The effect of a large meteorite impact or meteor airburst over a city would be catastrophic, with extensive damage and loss of life Asteroids that are 30 to 40 metres across are large enough to wipe out a city Around a million such asteroids exist, though unlike the larger asteroids that could cause global destruction, only a small number of these smaller 'city killers' are being tracked