Will microgravity stop us colonising exoplanets?

Chris Smith put this question to Cambridge University space scientist Xander Byrne...

Xander - Yeah, there's quite a few difficulties that we have with microgravity. We have been experiencing lots of different conditions as we've been evolving, but the earth's gravity has been a complete constant throughout all of that. So we've really adapted to precisely the gravity that we experience on earth. There are a few things that people find when astronauts come back from the International Space Station. There was one study in particular, which was quite cool because they had a pair of twins, one of whom was an astronaut and went up there and one of whom stayed on earth so that when he came back they were able to compare between the two. But the main things that you get are decreased bone density, as the question said, that decreases I think by about 1 or 2% per month, which is quite significant. Your muscle mass goes down obviously, because you don't have to fight gravity all the time. There's a particular problem with the heart because normally, here on earth, the heart has to pump blood upwards to the head, but in space you don't have to do that. So your heart kind of atrophies over time and then you have decreased blood pressure and it's starts to become a problem.

Ems - Was just thinking when you were talking about all of that, the news the other day that they're training the first astronaut who has an artificial limb and the difficulties that they were facing when they're training on that vomit comet with trying to get their leg to bend.

Xander - In pretty much any field of life, if you have a disability, often people don't think about that kind of thing when they're designing the experiences people are going to have.

Chris - So in other words, yeah, it will be a problem, but it can be surmounted. We need to think about the fact that our physiology isn't necessarily adapted to these other places and compensate, whether that's compensating with drugs, with exercise, or with other ways of keeping people fit and healthy.

Xander - And the way that they typically try and mitigate this kind of thing is primarily by exercise. I mean, there was a great example, Tim Peake, when he was still up there, he ran a marathon. And the way it worked is he was on a treadmill and he was kind of strapped downwards to the floor.

Chris - You've got to load your muscles and your bones, otherwise they fall apart and atrophy and you come home with the skeleton of a 70 year old.

Xander - When they come back to earth, they do typically have some moderate physiotherapy that they have to go through to be a functioning person again once they come back.