Space - how advances up there can help life down here

What are humans doing in space and why are we talking about bases on the Moon or missions to Mars when there is so much here on Earth that requires our immediate attention? We hear from two people involved in the business of space - one of whom visited space last year, the other who is convinced there will be a city of 1 million humans on Mars. And we link up with the International Space Station to speak to astronaut Samantha Cristoforetti.