How to defend against asteroids and meteors

Asteroid DA14 is the size of a city block and will pass within 17,000 miles of Earth in February (Getty Images)

Typically the preserve of science-fiction, now top of the news agenda, the prospect of an asteroid striking earth is raising alarm. This morning a meteor streaked across the sky in Russia, causing explosions and injuring 400 people. Later today a 150-ft asteroid will shave past earth at 17,000 miles distance, the closest recorded. If it hit, it could flatten London. So what defences do we have?

Meteors and asteroids have crashed into earth and will do so again. In 1908, one flattened 800 miles of Siberian tundra. Astronomers predict an asteroid spotted in 2004, known as Apophis, will crash in to the earth in 2036.

Even if Apophis misses, Wired report that "it's just a matter of time" before a rock lands plum on planet earth.

The Defence

1. The "nuclear option"

Route one. Armageddon posited the idea of blowing asteroids out of the sky in 1998. This could work outside a Hollywood studio, but wouldn't stop asteroid bit-lets causing havoc.

2. Gravity tractor

A creative solution. Space missiles can have their courses diverted by change in gravitational pull. Apparently, a single space-craft hovering above an asteroid could affect the trajectory enough to yank it away from bulls-eye.

3. A mirror

Perhaps the kind of brainwave only REALLY vain scientists would suggest (think Zoolander in a lab-coat), but an extremely large mirror could be used to focus energy on the asteroid and "boil off" parts of it

4. Phone Will Smith

He's saved humanity enough times already. And at the very least our species could be blasted off the face of the earth to the soundtrack of 'Miami'.