The Goldilocks Factor

More good news from space. Planets that sit in the 'not-too-hot not--too-cold' zones around other stars may be more common than we believed. Although Mars is the joker in the pack here - it sits inside the outer edge the Sun's habitable zone, but can't support life in its current state. Which makes it all the more urgent to find out if some kind of life emerged there in its early history, and what went wrong.