Astronaut Scott Kelly became the first American astronaut to spend a year in space. But when he returned, he realized that the mission had been the least of his worries.

Image: KIRILL KUDRYAVTSEV/AFP/Getty Images

It’s March 2, 2016, and Scott Kelly has just arrived back on Earth. He’s spent the past 340 days aboard the International Space Station – the longest stint that an American astronaut has ever completed. But in the days to follow, the real impact of his record-breaking mission will become all too apparent.

In February 1964 Richard and Patricia Kelly welcomed their son Scott and his twin brother, Mark, into the world. Scott Kelly subsequently grew up in the New Jersey suburb of West Orange and in his later years of high school took a job working as a paramedic in the local community. Then after graduating in 1982, he began attending the University of Maryland in Baltimore.

It was while at college that Kelly discovered The Right Stuff – Tom Wolfe’s 1979 book about the early days of space flight. And inspired by the pilots preparing to take mankind to the stars, Kelly subsequently decided that naval aviation was the career for him. However, unfortunately his application to join his brother at the United States Merchant Marine Academy was turned down.

So, instead, Kelly enrolled at the Maritime College of New York’s State University. Naturally, as a student there he experienced sailing around the world, and after graduating in 1987, the young Kelly joined the U.S. Navy as an ensign. Now a military man, he traveled to Pensacola’s Naval Air Station in Florida, where he began attending flight school.

Kelly was then singled out to be a jet pilot and sent to Beeville in Texas for further training. And just two years later, he earned himself the title of Naval Aviator. He subsequently went on to log over 8,000 hours in the air and take control of in excess of 40 different types of flying machine over the course of the next 25 years.

Yet it wasn’t Kelly’s naval career that would win him recognition around the world. In 1996, you see, he joined NASA, where he began training to become an astronaut. His first time in space then arrived on December 19, 1999, when he became part of a seven-man crew on board the Space Shuttle Discovery.

On that mission, Kelly spent eight days helping to carry out maintenance on the Hubble Space Telescope before on December 27 safely returning to Earth. The pull of outer space clearly proved too great, however, because in August 2007 Kelly joined the shuttle Endeavor as commander for a 13-day trip to the International Space Station (ISS).

Yet although that was Kelly’s first visit to the ISS, it certainly wouldn’t be his last. He actually returned in October 2010, this time on a Soyuz rocket launched for the Russian space program. Once on board, he then joined the ISS’ 25th mission as a flight engineer, and when Expedition 26 started the following month, he took on the role of commander.

So Kelly spent a total of 159 days living on the ISS. At the time, he’d already divorced from his first wife but still had two young daughters and a girlfriend waiting for him back on Earth. But when the commander eventually returned home, he’d already begun to feel the physical effects of spending so long in space.

Kelly’s six-month stint on the ISS was nothing compared to what was to come, however. Near the end of 2012, you see, NASA chose him to undertake a record-breaking, year-long mission on the ISS. And even though Russian cosmonaut Valeri Polyakov had set the bar high in the 1990s with a staggering 438 days in space, it was the first time that an American had attempted such an astonishing feat.

Russia’s Federal Space Agency helped plan this mammoth mission too, so Russian cosmonaut Mikhail Korniyenko joined Kelly on his year in space. And with an expedition to Mars in its sights, NASA wanted the men to help measure the long-term effects of space travel on the human body.

Previously, after all, ISS missions had lasted around six months. These trips were useful in providing researchers with information about the physical effects of spending short periods in space. In order to safely send humans on much longer journeys, however, experts knew that they had to begin gathering data on extended stays.

Interestingly, too, there was another factor that made Kelly the perfect guinea pig for NASA’s tests: his twin brother, Mark. Mark, who had also become an astronaut, would be staying on Earth, so this allowed experts a unique opportunity to compare two almost identical people in very different environments. Born of a project dubbed the Twins Study, the data that the brothers contributed would form part of NASA’s Human Research Program.

Kelly and Korniyenko took off from Kazakhstan’s Baikonur Cosmodrome in March 2015. They then rocketed to the ISS – their home for the coming year. And the pair occupied their time over the next 11 months conducting a number of scientific tests. In fact, Kelly claims that astronauts performed over 400 experiments during his time in space.

According to Kelly, these experiments tended to fall into two classifications. The first consisted of those that hoped to lead innovations back home. The second included those designed to improve the efficiency of exploring the galaxy. As a result, the New Jersey native found himself working on everything from botany to medical tests.

During Kelly’s time in space, he also stayed connected with social media networks on Earth using the hashtag #YearInSpace. Indeed, he actually uploaded some 750 pictures of his incredible journey on the ISS – signing off with a #GoodnightFromSpace post on an almost daily basis.

Image: Bill Ingalls/NASA via Getty Images

When the astronaut wasn’t occupied performing experiments and updating social media, though, he liked to use the on-board equipment to stay fit. That’s because exercising is an important task in an environment where muscles can quickly waste away. On specially adapted machines, then, Kelly worked out for around two hours each day.

Kelly and the crew still found time to let their hair down on the ISS, though. For example, on one occasion he uploaded a video showing him floating around the station dressed in a gorilla suit. And another time, he chatted with reddit users as part of an Ask Me Anything interview, answering questions about his time in space.

Yet in all of Kelly’s time on the ISS, he only ventured outside on three occasions. “This was one of the things that some people found difficult to imagine about living on the space station. The fact that I couldn’t step outside when I felt like it,” he told The Sydney Morning Herald in 2017. “Putting on a spacesuit and leaving the station for a spacewalk was an hours-long process. [It] requires the full attention of at least three people on [the] station and dozens more on the ground.”

And aside from the close confines, there were plenty of risks that came with Kelly’s mission. “Every day I was exposed to ten times the radiation of a person on Earth, which will increase my risk of cancer for the rest of my life,” he wrote in Endurance: A Year in Space, A Lifetime of Discovery, his 2017 book about his experiences. “Not to mention the psychological stress, which is harder to quantify and perhaps as damaging.”

Image: Bill Ingalls/NASA via Getty Images

Yet NASA nevertheless lauded the mission as a year in space, and on March 2, 2016, Kelly and Korniyenko returned to Earth after just over 11 months. However, the American soon found that his body and mind didn’t particularly like being back home. Having spent so much time on the ISS, you see, Kelly discovered that it was difficult and painful to readjust.

On social media, Kelly painted a happy picture of life back on Earth, with photographs of his first terrestrial sunset and first dinner at a proper table. Behind the scenes, however, the astronaut’s health was suffering. And within days, the record-breaker was in agonizing pain, suffering from fever, nausea and delirium.

Kelly also noticed that his legs were swollen and filled with fluid and that a rash had spread all over his body. He had developed a sensitivity in his skin too, possibly due to having been weightless for so long on the ISS. “It feels like it’s burning,” he told a press conference in 2016.

And while some of Kelly’s symptoms disappeared after a few weeks, others tormented him for months after his return. “Adjusting to space was a lot easier than adjusting to Earth,” the New Jersey native confessed. However, the physical ailments that plagued the astronaut were just the tip of the iceberg.

Image: Brian Ach/Getty Images for LocationWorld 2016

Just an hour after Kelly had arrived back on Earth, for instance, he stood back-to-back with his twin brother, Mark. And although the pair had been roughly the same height before their mission, it soon became clear that the space-traveler had grown by over an inch during his time in space.

Apparently, this phenomenon is common in astronauts, who can each grow as much as a few inches during their missions. According to experts, microgravity is the reason for this phenomenon. The human spine apparently straightens out without gravity pressing down on it, causing the difference in height.

Startlingly, however, it wasn’t just Kelly’s physical appearance that altered during his time in space: his very genetic makeup changed. For example, the astronaut’s telomeres – parts of the chromosomes associated with ageing – also grew a little while he explored off-world.

Image: Joel Kowsky/NASA via Getty Images

Researchers in addition noted that Kelly’s DNA had fewer chemical changes compared to that of his twin – something that could affect the behavior of his genes. This anomaly disappeared soon after Kelly came home, though. And it didn’t take long for his telomeres to return to normal either.

Image: Bill Ingalls/NASA via Getty Images

Not all of the anomalies vanished once Kelly returned to living a normal life, however. In fact, experts estimated that some 7 percent of his genes may have changed on what could be a more permanent basis. Those related to the immune system, bone formation and DNA repair could never return to pre-mission levels, for example.

Image: Aubrey Gemignaniln – NASA via Getty Images

Additionally, scientists discovered long-term changes in parts of Kelly’s genetic makeup that deal with oxygen levels in tissue and blood-borne carbon dioxide. They did note that his cognitive abilities hadn’t reduced any more than that of astronauts who had spent only six months in space, though.

Yet Kelly’s extended stay in space produced another strange side effect. Apparently, he is now one 100th of a second younger than his twin brother – thanks to a phenomenon known as time dilation. Associated with the theory of general relativity, time dilation affects objects that are not moving at the same speed.

Essentially, time dilation means that seconds pass quicker for the slower of the objects. So because Kelly was moving quicker than his brother while he was on the ISS, he is now technically younger by around 13 milliseconds. And while the age gap shouldn’t matter much to the Kelly twins, the effect raises an interesting issue for the future of space flight.

Image: Bill Ingalls/NASA via Getty Images

At the end of January 2018, you see, NASA released a statement confirming the initial observations previously made in the Twins Study. “All of these findings are being integrated and summarized by the research teams. Researchers are also evaluating the possible impact that these findings will have on future space travel beyond low Earth orbit,” it read.

In some circles, NASA’s findings caused much excitement – and conjecture. A number of news outlets published headlines suggesting that Kelly’s time in space had drastically altered his DNA, for instance. Later in March 2018, though, the agency released another statement clarifying its actual conclusions.

Image: Kimberly White/Getty Images for Breakthrough Prize

“Mark and Scott Kelly are still identical twins; Scott’s DNA did not fundamentally change,” it read. “What researchers did observe are changes in gene expression, which is how your body reacts to your environment. This likely is within the range for humans under stress, such as mountain climbing or scuba diving.”

Image: Ben Gabbe/Getty Images for Breitling

Ultimately, it’s hoped that Kelly’s efforts will help further mankind’s mission out into the stars. The record-breaking astronaut has been happy to return to normal life and his family on Earth, though. “It’s a simple thing, sitting at a table and eating a meal with those you love,” he wrote on social media. “For me, it’s something I’ve been dreaming of for almost a year.”

Yet even though Kelly’s mission took a heavy physical toll, he has not ruled out a future trip to Mars. “I doubt I will fly again with NASA,” he confessed soon after his return. “But I don’t think I would ever say I’m 100 percent done. There’s a lot of exciting possibilities out there. Maybe in 20 years, you’ll be able to buy a cheap ticket and go for a little visit.”

Kelly does also have plenty of advice for the aspiring astronauts who might one day make the unfathomable journey. “[Taking] it one day at a time is important,” he explained. “I tried to have milestones that were close and that helped me keep my sanity.” Meanwhile, the space-traveler is looking forward to the day on which his record will be broken.

Kelly announced that he would be retiring from NASA not long after his return from the ISS. However, it was far from the end of his close relationship with the stars. In November 2016, in fact, he became Champion for Space for the United Nations Office for Outer Space Affairs. And the former astronaut has since spoken about his experiences and worked to inspire people in all aspects of their lives.

Furthermore, in October 2017 he released Endurance and became a best-selling author in the United States. In the book, Kelly recognized the impact that his sacrifice might yet have on the future of mankind. “Our space agencies won’t be able to push out farther into space, to a destination like Mars, until we can learn more about how to strengthen the weakest links in the chain that makes spaceflight possible,” he wrote. “The human body and mind.”