'Armageddon' plan needed for asteroid impacts It measured just 36m (120ft) across, but the last known asteroid of such a size to hit Earth wiped out an area of Russian forest the size of London in 1908. Scientists are becoming increasingly concerned about the possible impact of asteroids measuring less than 1km across, which are not typically picked up by surveying programmes and could only be detected at very short notice. Delegates from across the world will gather at the United Nations in February to come up with a framework for earlier detection of asteroids, and a plan of action if a collision is deemed possible. Prof Richard Crowther, chief engineer at the UK Space Agency, said: "The theory is that if you can see it soon enough, you can deal with it. What we want to avoid is dealing with something that is only a couple of years away from impact - not only for technical reasons but also on the policy front. Moving an asteroid's point of impact away from Britain, for example, could potentially move it towards America or Europe like a red laser moving across a map, and as that happens obviously people are going to want to have some say about where it passes. Rather than only seeking asteroids 1km or larger in diameter, astronomers should be on the lookout for anything larger than 100m - but this would require funding from more countries than just America, which currently shoulders the burden, he said. Firing missiles at an asteroid may not be effective, he explained, because most are loose collections of rock which could re-form again after being broken up in the explosion. The most likely approach would be to alter the asteroid's trajectory, by flying a probe near the asteroid and either coating one side of it with a metallic spray, to change the way the sun's light affects its orbit, or to use the weak gravitational link between the asteroid and the probe to gradually pull it off course. NASA has already announced it intends to land a probe on an asteroid to learn more about what exotic minerals they might carry, but also to learn how to work effectively in a "microgravity" climate. "We need to understand what these objects are made of and how we might interact with them in the future so that if we do get the 'Armageddon' scenario we could place something on the surface [knowing] it would stay there and would be able to impact on the body as a whole, not a small part of it," Prof Crowther said.