Would you leave everything behind to start afresh on Mars, knowing you would never return to Earth?

More than 150,000 people would be willing to make the one-way trip, according to Mars One, an organisation that has been calling for applicants to make such a journey in 10 years' time. The Mars One plan may never come to fruition – people have been eyeing the red planet for decades and yet it remains unsullied by human footprints. But the one-way nature of the scheme does highlight one of the biggest barriers to visiting Mars – it's not getting there that's hard, it's coming back.

Mars: A return journey may be possible thanks to a new scheme.

Humans could have visited Mars or Venus in the '70s or '80s using variations of the Apollo spacecraft that went to the Moon. The catch was that they couldn't land. An Apollo-based interplanetary mission would have just flown by or possibly spent a few weeks in orbit, because landing would require a much heavier spacecraft and a lot more fuel. Because of this the spacecraft would have to be launched in several pieces and assembled in orbit, and demand the development of a lot of new technology and infrastructure – one of the original purposes for the International Space Station was as a kind of shipyard for interplanetary craft. As such, a Mars mission would be extremely expensive.