Scientists call for a 'mission to Earth' to discover 'life as we don't know it'

Alien life might exist under our very noses - or indeed inside them, according to a leading cosmologist.

Professor Paul Davies, a British scientist, claims "shadow" creatures may exist in tandem with our own and is calling for a "mission to Earth" to find them.

He believes that the life forms, most likely microscopic, could exist in remote and hostile environments where it was previously thought no creature could survive.

They are so different to life as we know it that scientists would have overlooked them in the past.

At the heart of his theory, which he explained at the American Association for the Advancement of Science conference, is that life on Earth may have come and gone many times during the planet's existence.

These creatures would be the remnants of the previous inhabitants.....