January 14 could have been a bad day for George Bush. As the president was preparing to announce America's return to the moon in a speech at the headquarters of Nasa, he was almost asked to deliver a very different message: that the Earth could suffer a devastating asteroid strike within 24 hours. Astronomers have revealed that during a "nine-hour crisis" the night before Mr Bush's speech they believed there was a one in four chance an asteroid would hit the planet in 36 hours. Had it not been for a break in the clouds that allowed an amateur astronomer...