Are we alone in the universe?

Scientists have long referred to the Goldilocks zone – the region around a star where conditions are not too hot and not too cold but “just right” for life. Joined by a live audience at the Cheltenham Science Festival in the UK, Tom Whipple asks what are the true limitations of alien life? How do we spot it? And have we been looking too narrowly?

Planetary scientist at MIT Sara Seagar discusses her team’s mission to Venus where, on the surface, temperatures can reach 500 degrees Celsius and it rains sulphuric acid. Above the rain, up in the clouds, Sara Seagar tells us how there could be life.

And Lewis Dartnell, Professor of astrobiology at the University of Westminster, describes how he looks for extremophiles. These are organisms on earth that are found in places we once thought impossibly hostile to life. Plus, the missions to find life on Mars....

Presenter: Tom Whipple Producer: Dan Welsh Editor: Ilan Goodman & Martin Smith Production Coordinator: Jana Bennett-Holesworth