The sky is falling

A big newly discovered asteroid could collide with Earth in just over two years.

The 800 metre diamater asteroid would cause widespread devastation if it did hit the planet.

New Scientist says the odds of impact are just one in six million - but the asteroid, called 2006 HZ51, is the most likely to collide with Earth this century.

Dan Durda, an asteroid expert and president of the B612 Foundation, says the discovery of the asertoid - on April 27 - highlights how little time we might have to prepare.

"There really isn't a whole lot we could do," he told New Scientist. "Most of the options that don't resemble a Hollywood movie involve deflection techniques that require many years or decades."

Other than stockpiling food and supplies and evacuating the regions most likely to be affected, he said, we would have to "hunker down and take the impact".

However, it is likely we would have longer to prepare for a collision. The second-most imminent threat now on the list is the asteroid Apophis, which has about a 1-in-6000 chance of hitting Earth in 2036.