The Guardian

London, February 26

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 be struck by a devastating asteroid within 24 hours.

Astronomers have revealed that during a “nine-hour crisis’’ the night before 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 to give the all-clear, the scientists say they were on the verge of calling the White House.

“An analysis of the discovery data for this object yielded a possible impact with the Earth in less than two days’ time,’’ said David Morrison, an asteroid and comet impact hazard expert at NASA’s Ames Research Centre. “And if a possibility of an impact in two days existed, what should we do about notifying governments or the public?’’ The scientists could only say they thought the 30-metre asteroid would strike somewhere in the northern hemisphere; at that size it would have exploded well before reaching the ground, though it could have killed thousands if it broke up over a big city.

The object — named 2004 AS1 — turned out to be around 500 metres across, and passed the Earth at a safe range of about 12m km: some 32 times the distance between the Earth and the moon.Details of the events of January 13 were revealed this week by a veteran sky-watcher, Clark Chapman, at a planetary protection conference in California. He said the object had first been spotted in four grainy images taken by two automated telescopes set up to watch for asteroids in New Mexico. It had been impossible to calculate its orbit accurately from the images, but when the information was posted on the internet an amateur astronomer noticed the mystery object was predicted to get 40 times brighter by the same time the following day, bringing it six times closer to the Earth.

Astronomers confirmed that the asteroid could be on a collision course, but the telescopes were obscured by clouds.