How we’ll upgrade our bodies to colonise the cosmos
“without the loading of gravity your skeleton loses calcium and becomes brittle, and your muscles deteriorate and shrink”
You might have thought from watching videos of astronauts aboard the International Space Station (ISS) that spaceships were pretty benign environments. Floating around in microgravity looks like a lot of fun, and as you’re isolated from the rest of the human population you’re effectively quarantined against catching flu or any other transmissible disease. But in fact, space is pretty harmful to the human body. We evolved as social animals under the conditions on the Earth, and travelling beyond the planet has a number of negative effects on the body and mind.
So what are the main risks encountered by spacefarers, and what does the latest research have to say about how to solve these problems for long-duration missions in the future?
Freefalling around the Earth in orbit, or coasting through interplanetary space on your way to Mars, gives you the sensation of weightlessness. You’re still moving under gravity, but it doesn’t load your body, and this has a whole host of knock-on effects. For example, your inner ear can no longer help you orientate yourself, and the redistribution of bodily fluids causes your face to puff up and your eyeballs to distort.
But the long-term effects are more concerning. Without the loading of gravity, your skeleton loses calcium and becomes brittle (like with osteoporosis). Your muscles, especially those involved in supporting your spine and holding you upright, deteriorate and shrink. Plus, your heart becomes weaker when it doesn’t have to pump blood upwards. While you remain in a weightless environment, this isn’t too much of a problem – and in some senses your body is being adaptive in remodelling itself to life without gravity – but it can be hugely debilitating or dangerous when you return to the surface of the
Earth or any other planet.
In the long-term future, the solution might simply be to generate artificial gravity for yourself on a spaceship. If you rotate large sections of a spacecraft – giant turning wheels or cylinders – you can exploit the centripetal force from the inside wall that keeps you moving in a circle to create an apparent gravity. We’re well familiar with this idea from sci-fi films like 2001: A Space Odyssey, or more recently Passengers, but the problem is that the engineering required to build such a large rotating structure in space is pretty challenging.
In the shorter term, spacecraft might incorporate mini-centrifuges. These wouldn’t be large enough to walk around or work inside, but they would fit within the existing structure with just enough space for a single astronaut at a time. Spinning relatively quickly, these could generate artificial gravity for short bursts while the astronaut exercises. The idea is that gravity could perhaps be dosed in small amounts; just enough to prevent the body deteriorating in space. David Green and his colleagues at King’s College London have been working with MIT and the European Space Agency (ESA) on another solution, the ‘gravity loading countermeasure skinsuit’. This skinsuit looks a bit like a triathlete’s sleeveless wetsuit, and
incorporates a specific weave of elastic material that provides a graded tension between the feet and shoulders. This elastic loading on the body simulates 1g (Earth’s gravity) and is designed to help prevent stretching of the astronaut’s spine, muscle and bone wasting. The scientists are running tests on their skinsuit on Earth, and it was recently worn on the ISS by Andreas Mogensen, the first Danish astronaut.
What about developing drugs that could help make exercise in zero-g more effective or stop muscle loss altogether by blocking the degenerative process? Nathaniel Szewczyk, at the University of Nottingham, has been involved in research along exactly these lines. But rather than experimenting on human test subjects, he has been using microscopic worms.
Caenorhabditis elegans is a nematode worm, but it has two different muscle types that are similar to the heart muscle and skeletal muscles used for movement in humans. As C. elegans is such a simple animal we’ve already been able to work out exactly how it develops, and we’ve also sequenced its whole genome. This means that C. elegans is a perfect test case for helping scientists understand the effects of microgravity on animal bodies, and they’ve now been flown on a number of space missions as microscopic astronauts. Szewczyk and his colleagues have found changes in the cellular production of around 100 proteins during spaceflight, many of them involved in musclebuilding. “These experiments with C. elegans in Earth orbit have enabled us to track how the expression of different proteins responds to weightlessness, and so explore the genetic basis behind deterioration of the body’s muscles,” he says. “In our current ESA flight we’re specifically testing a few drugs to see if they can reduce muscle loss in worms.”
So the hope is that in the future, astronauts will be able to pop a pill to help protect their heart and muscles while in space.
FAR LEFT: The Dainese BioSuit has been designed for trips to Mars LEFT: Danish astronaut Andreas Mogensen tries out the ESA skinsuit on the ISS RIGHT: In 2001: A Space Odyssey, apparent gravity was provided by a rotating wheel