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The Human Body in Space: Scott Kelly’s year long stay on ISS

ByLynda-Marie Taurasi

Mar 9, 2016

Hypersensitive skin that feels like it is burning when touched. Muscle soreness. Extreme fatigue. A stretched-out spine. These are just some of the side effects American astronaut Scott Kelly has endured since returning to Earth on March 1, after a year-long stint in space.

The mission was record-breaking, as Kelly spent 340 days aboard the International Space Station (ISS) – more time than any other US astronaut has ever spent in space.

Kelly was sent on the mission to enable Nasa to study the effects of long-duration spaceflight on the human body in preparation for a hopeful interplanetary space mission to Mars and back.

After a couple of days on Earth, Kelly’s height returned to normal but it will take Nasa another year to fully analyse the full effects that his year in space will have on his body. As a baseline, Nasa used his twin, Mark Kelly, for the “control” in the “twin study”. The study will focus on the responses of these two genetically identical people (the Kelly brothers) to their different conditions over the course of a year.  

Scott Kelly has reported that he already feels that the recovery is different from how it was after previous six-month long missions. He told reporters on Tuesday that although he felt better after initially leaving Soyuz landing capsule, he is feeling more muscle fatigue this time around – detailing a “linear function” between time spent in space, and the soreness and pain you feel back on Earth.

He also commented that the length of the mission was more psychologically gruelling due to the separation from family and friends.

But what exactly does happen to the body in space?

Well for starters, Kelly grew taller (albeit temporarily) because his spine relaxed and then extended while in microgravity.  There is a real threat of muscle atrophy as astronauts can lose nearly two per cent of bone mass per month while in space.  To keep their bodies as strong as they should be, astronauts will often exercise two hours a day, either by running on a treadmill or by hitting the weights.

Nevertheless, this still does not act as a full substitute for the workout Kelly’s muscles and bones would have received just by bearing the astronaut’s weight back on terra firma. With weakened muscles upon re-entry back to Earth, some astronauts may have a hard time walking again and need assistance until their bodies reacclimatise.

But the scariest effect could be a plot for a horror film. While on Earth, the heart has to work against gravity to circulate your body fluids from head to toe; this is not so in space. This causes the heart to shrink, and while in space, fluids float to the upper body, meaning that astronauts have to wear special trousers that suck the body fluids back down to the lower body. Without the trousers, the rush of fluid to the head can cause pressure on the optic nerve, impairing an astronaut’s vision and also making it harder to smell.  

Yet, Kelly’s data will give us an incomplete picture of the effects from cosmic radiation. While aboard the ISS, Kelly and his colleagues were still relatively near the Earth’s atmosphere and thus protected by the Earth’s magnetic field – unlike a trip to Mars.

While there are some insights immediately after Kelly’s return, it will take another year before his full physiological and psychological analysis is complete.


Image: NASA

By Lynda-Marie Taurasi

MSc student, Science Communication and Public Engagement

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