The nearest habitable world beyond our Solar System might be right on our doorstep . Scientists say their investigations of our closest star, Proxima Centauri, show it to have an Earth-sized planet orbiting about it. What's more, it is moving in a zone that would make liquid water on its surface a possibility. Gareth Mitchell hears from Guillem Anglada-Escudé whose "Pale Red Dot" team made the discovery and discusses what the "earth- like" claims actually mean.

The planet hunters of today search for worlds beyond our Solar System. The planet hunters of a century or so ago, were still going crazy trying to find one more planet orbiting this sun. In The Hunt for Vulcan shortlisted for this year's Royal Society Book Prize, Prof.Thomas Levenson examines the craze known as Vulcan -mania, in the desperate search for another planet in an attempt to explain the odd orbit of the planet Mercury. But why did the phantom planet theory survive for so long?

We examine observations from space of fleeting blue lakes in East Antarctica. They come and go with the seasons, forming during the warmer months of the south pole summer. As Amber Leeson of Lancaster University explains, many of the lakes then drain away, an effect already been found in Greenland but never, until now, in this part of the Antarctic. And their effect is cause for concern.

Deep sea sharks are nearly impossible to track around the planet, however they inherit the chemistry of the things they eat. Researchers at Southampton University have worked backwards and by examining the chemistry of the sharks, they've been able to determine what things a shark has been eating but also where in the world it has been feeding. Chris Bird and Clive Trueman discuss how they're building up the first accurate pattern of their extraordinary movements.

Presenter: Gareth Mitchell Producer: Adrian Washbourne.