If you think of the Apollo capsule coming into Earth with a parachute, the Mars atmosphere is just so thin, you've got to find some way of slowing yourself down really rapidly.

Being able to have a laboratory on Mars, being able to have some sort of sustained human presence on Mars in the future, I think, is critically important for science.

We like to talk about pioneering Mars rather than just exploring Mars, because once we get to Mars, we will set up some sort of permanent presence.

So many people I talk to who work in technology, you ask them, 'What got you interested in science?' and those from my generation say, 'The Apollo landings.'

My key aim is to get man on the surface of Mars by the mid-2030s.

We have to ask, 'How can we break a huge challenge like sending humans to Mars into a series of doable, affordable steps? How can we break that problem down into chunks in order to keep making progress?'