Scott Kelly is a former NASA astronaut who is best known for spending nearly a year on the International Space Station and for spending 520 days in space, which puts him on the list of Americans who have spent the most time in space. (The current record-holder is Peggy Whitson, at 665 days.)
He did two long-duration space station missions and two shorter-duration space shuttle missions between 1999 and 2015. Kelly is the twin brother of Mark Kelly, who also was a NASA astronaut.
Kelly's scientific goal during the one-year mission was to better understand how the human body adapts to lengthy periods in space. Most ISS missions are only five to six months in length. While longer missions of approximately a year (in one case more than 400 days) took place on the Mir space station in the 1990s, modern medicine has made it easier to measure changes in the genes.
Kelly and Russian colleague Mikhail Kornienko both spent 340 consecutive days on the ISS tracking how their bodies changed. Kelly also did a "twin study" with his brother to see if there are any genetic changes from spending long periods of time in space.
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Scott was the second of the two brothers to be born, on Feb. 21, 1964. According to the twins in a 2010 NASA interview, their parents didn't tell them who was the oldest until the boys were in their teens.
"Our parents weren't — they didn't want to tell who was older because they thought maybe that person would then have some leverage or something like that," Kelly said at the time. "So, we didn't know who was older or who was younger until probably, you know, thirteen to fifteenish."
The brothers were born and grew up in West Orange, New Jersey, also known as one of the places where Thomas Edison lived. They were close enough to Manhattan to spend the weekend there or head to a museum. In high school, they were co-captains of the swim team and participated in track, baseball and football.
Initially, Mark and Scott took different paths after university. Mark joined the Navy, and received a bachelor's degree in marine engineering and nautical science from the U.S. Merchant Marine Academy in 1986. In 1994, he received a master's degree in aeronautical engineering from the U.S. Naval Postgraduate School.
Scott received a bachelor of science degree in electrical engineering from the State University of New York Maritime College in 1987 and a master's degree in aviation systems from the University of Tennessee, Knoxville, in 1996. He then went to the University of Maryland and considered becoming a doctor. After spending a year there, Scott decided to follow his interest in flying airplanes and switched into the Navy — putting him a year behind Mark.
The twins, however, ended up in the same test pilot school class. "Most test pilots apply at some point to the astronaut program," Mark recalled in the same interview, and the twins put in their applications for the 1996 NASA astronaut class. Both were accepted. [Related: Twins in Space: NASA's Twin Astronauts Mark and Scott Kelly (Photos)]
Scott Kelly made it to orbit very quickly after becoming an astronaut. Only three years later, he was the pilot for STS-103, a shuttle mission that upgraded the Hubble Space Telescope. His crew spent eight days in December 1999 in space (including celebrating Christmas there), where their main duties were to install instruments and upgrade systems on Hubble.
Kelly held many roles in between missions, including director of operations in Star City, Russia, and being a backup for ISS Expedition 5. His next mission, STS-118 on space shuttle Endeavour, was in 2007. This was a construction flight for the International Space Station that added a gyroscope, a truss and a new spare parts platform.
Kelly then switched launch vehicles to a Soyuz for his next flight into space, his first long-duration space station mission. He launched in October 2010 and spent 159 days aboard the ISS, including serving as commander of Expedition 26.
Around this time, NASA and Roscosmos, Russia's space agency, were discussing sending up an astronaut-cosmonaut team to the space station for an entire year. Scientists hailed it as a way to improve the knowledge of the human body in microgravity, especially because NASA is hoping to have a human mission to Mars someday.
Kelly ended up being one of only a few astronauts at NASA who qualified for the mission. This was both because of his experience (he was already a veteran of three spaceflights at this point) and also because his radiation exposure had not yet hit the lifetime limit for NASA astronauts. He later said in interviews that he initially was hesitant to take a year away from home, but as he warmed up to the idea he was happy to go.
Kelly and Kornienko (along with veteran cosmonaut Gennady Padalka) launched to the ISS on March 27, 2015. The team took a fast track to the ISS that got them there in only a few hours, unlike the past procedure that would take about two days to get to the station.
The early days of Kelly's mission were a bit more eventful than anyone expected. A series of cargo ships from different companies and countries failed upon launch to the ISS in the space of a few months. In a documentary that ran on PBS in March 2016, one commentator said the astronauts on board came close to rationing food until successful launches resumed.
Kelly, however, remained focused on doing a good job in space. He performed three spacewalks, took charge of a moldy plant experiment and saved the zinnia flowers within it, and served as commander for Expeditions 45 and 46. He also sent regular tweets and social media updates, and held press conferences, to keep the public informed. (In the documentary, he later said he was surprised by the amount of interest the public had in his mission.) [Infographic: How the Epic One-Year Space Station Mission Works]
The veteran astronaut arrived safely on Earth again on March 2, 2016, after 520 days in space (340 of them consecutively on the one-year mission). In a press conference after the long journey from Kazakhstan to the United States, Kelly expressed enthusiasm for going back to space— but as a part of a private spaceflight, as he felt it was time for younger NASA astronauts to get flight assignments. Kelly retired from NASA on April 1, 2016. [Related: Astronaut Scott Kelly is Home, But the Science Continues]
Kelly has remained active in spaceflight activities even after retiring from NASA. In fall 2017, his book "Endurance: A Year in Space, A Lifetime of Discovery" (Viking, 2017) was published. The name appeared to be inspired by Alfred Lansing's 1959 book "Endurance", about Ernest Shackleton's Antarctic expedition. Kelly brought a copy of Lansing's book with him to space during his last mission, and left it behind in the space station's small library when he came back to Earth, he recalled in the biography.
"At some point, somebody said to me that this really was a mission of endurance, not only in space, but from the time I was a kid," Kelly said in an interview with collectSPACE in October 2017. "It was an example of sticking your nose to the grindstone and just plugging away at it ... When I heard that, I thought it was a pretty good idea for a title for the book, especially because of the connection I had with 'Endurance' and Shackleton."
In 2016, Sony Pictures announced it had secured the film rights for "Endurance."
PBS and Time did a follow-up documentary on Scott Kelly called "Beyond A Year in Space", which examined Kelly's return to Earth and medical testing — as well as the paths of two newer astronauts, Jessica Meir and Victor Glover.
"Two men with identical genomes, identical careers," Jeff Kluger, science editor for Time, said in an exclusive clip from the documentary provided to Space.com. "You send one man to space for one year … you track the other man living an earthly life for that same one year, subtract the differences — that's what space did."
Kelly frequently comments on spaceflight in the media and is also involved in several charitable endeavors. In late 2017 and early 2018, his Twitter feed included links to an organization helping those hurt by Hurricane Harvey in Houston, as well as research by medical relief organization the Syrian American Medical Society. Kelly will also go to the Arctic in April 2018 with the International Space School Educational Trust, which has astronauts and other space advocates encouraging learning in science, technology, engineering and mathematics.