One day in late September a box-shaped spacecraft weighing approximately half a ton will slam into an asteroid seven million miles away from Earth at a speed of 15,000mph, in a bid to knock it into a new orbit.

This suicide mission by a craft the size of a golf cart is not just a self-indulgent experiment dreamed up by NASA scientists with money to burn.

The very future of mankind could depend on its success because the $330 million (£269 million) Double Asteroid Redirection Test (DART, for short) may well provide the answer to a problem that has preoccupied astronomers for centuries: what to do when an asteroid is on a collision course with our planet.

'This is a mission for planet Earth — all the peoples of Earth — because we would all be threatened,' said NASA Administrator Bill Nelson, who added that Dart has 'turned science fiction into science fact'.