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Taller and younger, Scott Kelly returns from year in space

Scott Kelly pauses to give a "thumbs up" to the camera while on a fuel stop on his flight from Kazakhstan to Houston. Credit: NASA

Scott Sutherland
Meteorologist/Science Writer

Friday, March 4, 2016, 1:46 PM - Astronaut Scott Kelly has been back on Earth since March 1, as his One Year Mission aboard the International Space Station came to an end. In honour of his mission, here's what an astronaut typically endures upon their return to Earth.

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Tune in below for recordings of the NASA TV hosted discussions with Scott Kelly's brother, Mark, as well as project scientists, and then for the press conference with Kelly himself.

He likely won't be able to walk (Updated!)

The "microgravity" environment of the International Space Station takes a big toll on an astronaut's body during their time there, and once Scott Kelly is on Terra Firma again, it's doubtful he's going to be able to stand up, let alone walk away from his landing.

When flying around the Earth at 300 km above the surface, circling the planet once every 90 minutes or so, the downward pull of gravity isn't much weaker than what we experience here on the ground. It's that 90-minute orbit, however - constantly being pulled down towards the Earth but always missing - that puts the space station crew into a perpetual free-fall, cancelling out the effects of gravity for the duration of their stay.

Since humans evolved under the constant influence of 1 g of gravity, many of our internal workings depend on its presence. Living in a low-g or zero-g environment, our muscles and bones are not under the constant stresses and strains that gravity imposes, and thus they weaken as a result. The inner ear is affected as well, since - by necessity - it is very sensitive to gravity in order to help keep us upright. Since there's very little need for the brain to receive information from the inner ear while in space, it takes some time to regain a sense of balance and coordination once the return to Earth.

Although some astronauts have been able to stand very shortly after exiting the capsule after landing, having spent a year in space, it's doubtful that Kelly will be able to do so. Even his daily exercises can't fully compensate for the fact that our muscles constantly work against gravity, even with the smallest movements, while we're on Earth.

When Sergei Avdeyev, the Russian cosmonaut that spent over one year and 14 days in orbit during his last mission on board the Mir space station, landed in August of 1999, he was taken away from the landing on a stretcher. He was so physically weak, he couldn't even sit up straight under his own power. According to a report from The Guardian in 2001, it took a year of work for Avdeyev to recover from the effects of his last stay in orbit.

Update: When Scott Kelly was extracted from the Soyuz capsule on Wednesday morning (Kazakhstan time), he was heard to remark how he did not feel much different than he had when he returned from his last stay on the ISS, back in 2010-2011.

At the time, it was possible he was simply "riding high" on adrenaline after his descent from space, however the latest videos of Kelly tell a very different story.

When Scott Kelly arrived in Houston, he spoke briefly with the press, and while his movements appear slightly stiff when walking, he looked to be in excellent condition, despite his time spent in zero-g.

Update 2: Based on what Scott Kelly said during his Friday press conference, while he felt good upon landing, his muscle fatigue has become worse since then. His skin also feels much more sensitive, as it hasn't rubbed against anything for awhile, and his feet hurt as well.

His sleep will change, for better or worse

During his own time in space, Chris Hadfield gave an excellent description of sleeping in space, and he talked about how comfortable it is.

"You can relax every muscle in your body," he said.

Based on his Reddit "Ask Me Anything" from January 23, 2016, however, Kelly may actually get a better night's sleep once he's on Earth.

"Sleeping here is harder here in space than on a bed because the sleep position here is the same position throughout the day," he wrote in answer to one question. "You don’t ever get that sense of gratifying relaxation here that you do on Earth after a long day at work."

Other assorted health issues

In addition to the effects on his muscles, bones and inner ear, Kelly's time in space will have caused his heart to shrink, simply because it will not have needed to pump as hard to get blood out to his extremities. This will likely result in low blood pressure when he returns home, and a general feeling of lightheadedness and disorientation if he stands up or turns too quickly.

His immune system will be weakened after being in orbit, so he'll have to be careful about exposure to anything that could make him sick.

The lack of gravity will likely have adjusted the shape of his eyes. While he has been seen wearing prescription glasses before his mission and during his time aboard the ISS, his prescription may have changed in between and it could change again once he's back on Earth.

He'll (temporarily) be taller (Updated!!)

Although microgravity takes its toll on an astronauts muscles and bones, spending time floating around on the space station also takes the stresses off the spine, allowing it to decompress. 

As a result, he could be a couple of centimetres taller when he first returns home.

His height will return to normal as he adjusts to the pull of gravity again, but at least for a time, he'll stand a little bit taller than his twin brother, Mark.

Update: As it happens, Scott Kelly did not grow 2 cm taller... he grew 2 inches taller while in space! The scientists behind the One Year Mission figure that he is probably already back down to his pre-launch height by now, though. 

He'll be younger

This one may seem a bit strange, but by the rules of relativity, as the crew on board the International Space Station travels around the Earth at a speed of 27,720 km/h, they actually age slower than those of us standing on Earth's surface.

The effect is minuscule, of course. You wouldn't even notice it if Einstein hadn't pointed it out, however, after a year in space, Kelly will be around 0.014 seconds younger than he would be if he had stayed on the ground.

Effectively, he's a time traveller!

He'll have a fresh outlook on the world

This was not Scott Kelly's first trip to space. He has flown on the space shuttles Discovery and Endeavour, in 1999 and 2007, respectively. He also spent roughly five months on board the International Space Station, from October 2010 to March 2011, as a crew member for Expeditions 25, and commander of Expedition 26. During those times, he enjoyed the incredible views of Earth from orbit, which has likely already changed his outlook about the world.

Still, returning to Earth after spending a year in space could result in a stronger appreciation of nature, the company of others, and even food and drink.

Doug Wheelock, who commanded the ISS just prior to Scott Kelly in 2010, told ABC News: "Your sense of smell and taste are dulled in space. I craved the aroma of leaves and grass and flowers and trees."

"These things are not present on the space station," he added. "When you get back to Earth they are literally intoxicating."

Kelly clearly has a great relationship with his fellow ISS crew members while on board (see the video below of him chasing UK astronaut Tim Peake around while dressed up for the fun).

At the same time, though, Kelly has spent at least a year without seeing his loved ones, and without the company of more than five other people at a time.

Also, returning to Earth will allow him to enjoy freshly prepared food that doesn't come from a pouch. He and his crewmates were the first to sample lettuce grown in space, and he'll likely get a piece of fruit or cucumber to eat when and his two travelling companions reach the ground on Tuesday, but there's a good chance he has something very specific in mind for his first meal back in Houston.

His recovery

The various difficulties Kelly will experience will fade with time as he gets used to being under the direct influence of gravity again. 

According to Robert Frost, a NASA instructor and flight controller, this will take anywhere from days to weeks for some of the effects, such as coordination, movement and balance. Others, especially the recovery of muscle and bone mass, will take much longer, perhaps a year - equal to how long Kelly was in space - or possibly longer. He may not even regain all of the bone mass that he lost during his mission.

Kelly's recovery will be long and will involve hard work on his part. He'll adjust to gravity, even settling down to his normal height in the process, but at least he'll still be able to claim that 0.014 s of time travel. That's his to keep.

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Sources: NASANational Space Biomedical Research InstituteThe Guardian | RedditNASA | Quora | NASA

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