Richard Hollingham meets scientists and engineers planning human colonies in space.
What will it be like to colonise space? What are the implications for humanity if we do?
Why go to Mars? Claudia Hammond examines the space-farer's drive to occupy the red planet.
Kevin Fong explores differing visions of a human presence and purpose on Mars.
Could we live on another planet?
Sir Fraser Darling asks who is responsible for the protection of the natural world.