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Rocks in space

A government report recommended that we spend a great deal of money ensuring that a rogue asteroid or comet does not hit the Earth. An example of rocks in the head, rather than rocks in space, say some. Yet the case for action is compelling.

By Duncan Steel   January 2001

By counting the asteroids flying past our planet, astronomers estimate that Earth gets hit by a big one once every 100,000 years. By tallying craters here and on the moon, geologists come to similar conclusions. The energy released in such collisions equals 10m atom bombs, sufficient to cause global environmental mayhem and to kill up to half of humanity.

Just how big a piece of space rock is needed to do this is not clear. Half a mile in diameter might be enough, depending on its composition and arrival speed. All scientists agree that the “asteroid the size of Texas”…

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