NASA's new way to defend Earth from asteroids

NASA scientists have found a simple yet ingenious way to spot tiny near-Earth objects (NEOs) early as they hurtle towards the planet, an advance that may aid the efforts to prevent dangerous impacts.

The Chelyabinsk meteor, which was a mere 17-20 metres across, caused extensive ground damage and numerous injuries when it exploded on impact with Earth's atmosphere in February 2013.

"If we find an object only a few days from impact, it greatly limits our choices, so in our search efforts we have focused on finding NEOs when they are away from Earth, providing the maximum amount of time and opening up a wider range of mitigation possibilities," said Amy Mainzer from NASA's Jet Propulsion Laboratory (JPL).

However, it is a difficult task -- like spotting a lump of coal in the night's sky, Mainzer said.

"NEOs are intrinsically faint because they are mostly really small and far away from us in space," she said in a statement.

"Add to this the fact that some of them are as dark as printer ...