Britain works on preventing asteroid collisions.

A British government team is to propose spending up to 25m [pounds sterling] (roughly $26 million) on a plan that would safeguard Britain and the world from devastation by a giant asteroid or comet.

The Spaceguard initiative could see Britain using a chain of telescopes to detect and monitor "near-Earth objects" (NEOs).

The British commission report says that Earth faces a tiny but definite risk of being struck one day by an asteroid -- a large lump of stone or metals travelling at tens of miles a second. This kind of impact is believed to have wiped out the dinosaurs 65 million years ago.

A monitoring station, possibly based in Northern Ireland and linked to telescopes around the world, would be the first stage in a program that would also investigate ways of knocking any approaching asteroid off a collision course with Earth.

One option could be to fire a nuclear missile that would explode close to the incoming rock and deflect it.

At least two big impacts were recorded during the last century. The first, at Tunguska in Siberia in 1908, devastated an area the size of greater London. The other, in Brazil in 1947, left several huge craters. Both fell in unpopulated areas and nobody was killed.

In September astronomers announced that a huge asteroid would cross Earth's orbit at a range of 2.6 million miles. In astronomical terms this is a tiny distance -- and others will come much closer.

In 2027, a rock (known as 1999 AN10), measuring half a mile in diameter and travelling at 50 miles per second, will hurtle past Earth at a distance of just 200,000 miles. It will pass close by several more times -- with nobody yet able to predict whether it will hit the planet.

America and Japan have established their own Spaceguard projects. NASA plans to track all asteroids with diameters greater than 1km that will cross the path of Earth by 2006. An asteroid that size would wipe out most life and there would have been many such events early in Earth's 4.6 billion-year history. Now, however, the risk is much lower because most potential collisions have already happened. The last big asteroid, about six miles in diameter, was the one that wiped out the dinosaurs.

Mark Bailey, director of the Armagh Observatory in Ireland, a world-renowned center for the study of asteroids and comets, believes the world is now so heavily populated that even a small impact could kill millions. "Asteroid and comet impacts have changed human history in the past and it could happen again," he said.

Dr. Bill Napier, an astronomer who specializes in comets and asteroids, believes the only solution is to set up a fleet of rockets carrying nuclear bombs that could be detonated half a mile from any threatening object.

"You would only have to nudge them a few meters to send them safely past Earth to avoid Armageddon," he said.

"A 200-meter object plonking into the Atlantic would effectively take out all the cities around the seaboards. Those smaller events occur rather more frequently -- they are talking about a once every several thousand years event," said Duncan Steel of the University of Salford, one of the leading authorities on asteroids and comets.

Jonathan Tate, a British army officer states, "One of the major effects of this report will be to dispel, for once and for all, the giggle factor associated with the impact hazard. No sane person can any longer regard this as either funny or science fiction."

If you'd like a list of close calls: http://cfa-www.harvard.edu/iau/lists/ CloseApp.html