Human beings have evolved to become "perfectly adapted to life on Earth", said Sky News. So, spending time in space, without gravity or sunlight, and exposed to radiation, "poses a real challenge, physically".
For "stranded" astronauts Barry "Butch" Wilmore and Sunita "Suni" Williams (pictured above) – whose routine eight-day visit to the International Space Station turned into an unscheduled nine-month stay – the challenge may be even bigger, when they finally come back home to Earth today.
The pair, travelling in a SpaceX Dragon capsule, left the ISS early this morning. After a "fast and fiery re-entry through Earth's atmosphere", they are due to splash down off the coast of Florida tonight, said the BBC. The fresh air will feel "fantastic", said Helen Sharman, Britain's first astronaut, but such an extended space mission will, said the broadcaster, have taken a "toll on the body".
'Exit spacecraft on stretchers'
"You adapt incredibly quickly to being in space," Nasa astronaut Frank Rubio, who spent 371 days in space in 2023, told Time magazine last year. But readapting to life back to Earth can be "a little bit longer and more difficult". The first two or three months will be focused on recovery, "reincorporating yourself into Earth, your family, and then also rehabilitating your body".
After splashdown, the astronauts will be taken to the Johnson Space Centre in Houston, Texas, for a medical check-up. Astronauts returning from long-duration space missions "routinely exit their spacecraft on stretchers", said CNN, because their bodies "need time to adjust to feeling Earth's gravity".
'Incredible connection to humanity'
Nine months without gravity will have caused "significant, and irreparable, bone density loss", said The Guardian. Being in space "causes muscles to waste" and fluids "don't drain as easily". The returning astronauts will "struggle to walk, get dizzy easily, and have bad eyesight", because the "build-up of fluid changes the shape of their eyeballs, and weakens their vision". They may need glasses for the rest of their lives.
In space, clothing floats off your skin, so your skin gets "almost baby-like sensitivity", said Alan Duffy, an astrophysicist at Australia's Swinburne University told the paper. On Earth, some astronauts "feel like their clothing is sandpaper".
Seeing the Earth from space has also led some astronauts to report "an incredible connection to humanity", said The Guardian, and "an immediate sense of its fragility".