On returning to Earth after an extended stay in space, astronauts have to undergo extensive rehabilitation. Without gravity, all sorts of things go awry.
Muscles atrophy without being used to supporting the weight of your body against Earth's pull, even with daily exercise in zero-G. Because fluid in the head isn't being pulled down, it can create pressure on the eyeballs, causing vision problems. Blood pressure needs to be restored. And bones lose density -- about one to two percent per month. After five months in space, former ISS Commander Chris Hadfield took several months to recover.
And now it's been revealed that spending time in space can make your skin thinner, according to a Reuters report. No, that doesn't mean you become sensitive to teasing.
A team of researchers led by Karsten Koenig, professor at the Faculty of Physics and Mechantronics in the Department of Biophotonics and Laser Technology at Saarland University in Germany has used lasers to examine why skin gets thinner in space, at the request of NASA and the European Space Agency.
"NASA and ESA came to us and asked, 'is it possible to also look in the skin of astronauts? Because we want to know if there's any ageing process going on or what kind of modifications happened to astronauts as they work for six months out in space.' Because many astronauts complain about skin problems," he said.
The team studied three astronauts -- Italian EAS astronaut Luca Parmitano, who spent 166 days in space, Italian ESA astronaut Samantha Cristoforetti, who spent 199 days in space, and German ESA astronaut Alexander Gerst, who spent 166 days in space. Each astronaut had their skin scanned just before going into space, and again on their return.
The technology, developed by Koenig's team, uses lasers to image sections of the skin in high resolution using a technique known as tomography.
"We use femtosecond laser pulses. We scan the skin and we get signals from the skin, particularly fluorescence, as well as another signal called second harmonic generation," he explained. "So with these two signals we can build up images and get a precise look into the skin with a high resolution. The resolution is a factor of one thousand times better than ultrasound."
All three astronauts displayed the same symptoms, Koenig's team found.
"So far we've got interesting results from three astronauts. It seems that there is a strong production of collagen; so suddenly these astronauts have more collagen. It means there is some sort of anti-ageing effect, at least in the dermis - the lower part of the skin. And we found that the epidermis, in particular the part of the living cells, that this epidermis is shrinking, so the skin gets thinner," he said.
Six months in space, the team found, thins the skin by nearly 20 percent. What they don't know yet is why. Although knowing why won't necessarily help with prevention -- after all, knowing zero-G causes bone density loss hasn't prevented it from happening yet (attempts are being made to create an artificial gravity environment inside a centrifuge, but it's still in development) -- it could help develop preventative measures in the future.
Koenig and his team have to wait, though; astronauts don't return from the International Space Station every day.
NASA and the Russian Federal Space Agency currently have two astronauts who are spending an entire year in space aboard the International Space Station to help gauge how longer stays in zero-G affect the human body. This experiment will hopefully provide valuable data for NASA's planned Mars mission in the 2030s, a round trip that will require at least a year away from Earth.