Scott Kelly spent a year in space – was he the same as his twin when he got back?

Scott Kelly worked for NASA as an astronaut between 1996 and 2016, in a space career that spanned 20 years. His last mission for the space exploration company took him up to the International Space Station (ISS) for a year to be the guinea pig in an experiment. Scott Kelly has an identical twin brother, Mark, also an astronaut, and NASA wanted to test the effect of extended time spent in space. NASA left Mark on the ground while Scott was up in space, and they were simultaneously keeping tabs on both of them. Using twins allowed them to compare what happens to our bodies up in space, as you have a genetically identical ‘control’ on the ground.


Scott has contributed a lot to humanity through his various space exploits, he has done vital research that will contribute to how society deals with some of its environmental issues in the future. All of the experiments Scott and all astronauts do in space are fact-finding missions with scientific research at the heart of the matter for the most part. The astronauts that bravely volunteer to leave Earth do so at great risk to their safety, and they do it all for the hopes of scientific breakthroughs as well as aiming to discover if there has been life on other planets or not. But what effect did spending a year in zero gravity have on Scott’s body? Was he still the same as identical twin once he landed back on Earth?

Who is Scott Kelly?

Scott Kelly is a NASA astronaut that famously stayed in space for almost a year on the International Space Station (ISS). He frequently checked back in with Earth by posting pictures on social media, and his time in space was the longest served by an American at the time. He was continuously undergoing medical examinations during his time in space as part of a comparative study with his identical twin brother who was left back on earth. Scott spent 20 years working for the space organization, from 1996 to 2016. He hasn’t only piloted American spacecraft, however – in 2010 his voyage into space saw him take control of a Russian spacecraft known as a Soyuz.

What is NASA?

NASA stands for National Aeronautics and Space Administration and has been operating since 1958. It controls the science and technology departments concerned with the USA’s interest in space and airlines. NASA performs a key role in teaching scientists more about the Earth. They help to develop satellites and probes which monitor and study the Earth and the surrounding planets and solar system. The studies performed by NASA can help us understand the different climates and weather conditions in the solar system and therefore figure out how to make Earth better using that information. NASA was created following the space race between the Soviet Union and the USA during the ‘50s.

Before NASA

Scott was born in New Jersey and is of Irish descent. He is well educated, with two degrees, one in electrical engineering and another in aviation systems. Before he was an astronaut, he was in the U.S. Navy as a naval aviator. After logging over 8,000 hours in flight and piloting over 40 different types of aircraft and spacecraft, he retired as a captain from the U.S. Navy in 2012. Retirement allowed him to focus solely on his career as an astronaut.

NASA calling

Scott was selected by NASA in 1996 when he began the training program set by the space exploration institution. After completing the training and passing the entry requirements, he was chosen to work in the technical section of the research department at NASA. Following his technical expertise and his military achievements and competence, he was chosen out of the crew to be the pilot of his flights into space. During his space exploits, he has been responsible for the implementation of various equipment on the ISS, as well as overseeing and performing several spacewalks.

Early space travel

His first three space flights included commanding on the ISS. His first venture into space was on the shuttle Discovery in 1999 to head to the Hubble Space Telescope and carry out maintenance, this spaceflight lasted eight days. His next mission was as a commander heading to the ISS, a trip that would last 12 days in 2007. He went again to the ISS but this time it was not a brief visit to space, he arrived in October 2010 and didn’t leave until March 2011.

A year in space

After exhibiting his ability to endure a long-term stay on the ISS he was selected to take part in a year-long mission. Again he was sent to the ISS, and he arrived with the Russian cosmonaut, Mikhail Kornienko, on 27 March 2015. Scott commanded the missions on the ISS before passing the command to astronaut Tim Kopra in February 2016. Scott returned to Earth on 1 March 2016. Kelly had completed close to a full year off the planet, and it took its toll on his body.

Brothers in space

Scott has an identical twin brother who also is an astronaut. His twin, Mark Kelly, was a former naval aviator before being selected to pilot a NASA space shuttle in 1996. He left the Earth four times in total from 2001 to 2011. Following his trip into space in 2011, he retired from service following an assassination attempt on his wife. He retired from active duty to aid with his wife’s recovery. The twins have become the only siblings who have traveled in space.

Testing twin DNA

Following the year-long mission in space, scientists noticed that Scott’s body had undergone some changes, particularly where his DNA was concerned. It seems as though his time in space had changed how his body was made up on a molecular level. Before he went on his extended trip into space, scientists took samples of his blood to collect his DNA, and did various tests with him and his twin brother, Mark. These tests proved invaluable when comparing the twin’s bodies after one spent a year in space.

The changes

The twins underwent several tests, there were ultrasounds taken of their bodies, their bodily fluids were tested, and they even got flu shots. When Scott returned to Earth scientists discovered his body had altered so much that some people began questioning whether they could even be considered twins anymore. Once Scott’s body recovered from the space flight he still only shared 93% of his genes with his twin. This begged the question about what happened to the other seven percent.

The seven percent

Following the study, scientists pointed to the altered seven percent of Scott’s genes as a sign that space travel can change humans. The findings point to the changes in immune systems, the oxygen and carbon dioxide levels in the blood, as well as fundamental changes in bone formations – he was two inches taller when he returned! While the vast majority of Scott remained the same, it is clear space exploration has changed him. He may be the same mentally, but physically he is a little different, although you just might need a microscope to notice.

The future – Mars

The findings from the scientific research have shown NASA and others that extended space flight can have an impact on the health of their astronauts. This is something NASA and others will have to take into consideration when sending humans to Mars. NASA looks to be the frontrunner for sending humans to Mars as they have identified that they plan on sending someone there by 2030. A round trip to Mars is expected to last around 2-3 years, so keeping the astronauts healthy will be the priority for NASA.

Space gardening

Scott grew lettuce in space with the people he shared the ISS with. They wanted to demonstrate the ability to harvest crops in space, which could, in theory, mean there are a host of farming options available to humans off the planet. They had up to 400 different scientific experiments going on during Scott’s year on the ISS. He even grew some flowers and sent a picture of them to his partner back on Earth on Valentine’s day, who said romance was dead?

What happens to your body in space?

Space is a dangerous place for humans to be. Without the aid of spacesuits the human body will shut down instantly, as the air from your lungs will be ripped out and the oxygen will stop going to your brain. It is not going to be pretty. Buzz Lightyear taught many of us you can’t open a spaceman’s helmet on an uncharted planet, his eyeballs could be sucked from their sockets. Well, not in Buzz’s case, but in reality that’s what is likely to happen.

What do the spacesuits do?

So we know we need the suits, but what do the suits actually do? They protect the astronauts from some of the extreme temperatures they come into contact with. Astronauts, like all humans, need oxygen to breathe, so the suits also provide them with enough to remain alive when they are out on a spacewalk. The oxygen is pressurized to mimic the pressures found on earth, so that they can breathe properly inside the helmet. Furthermore, the experience can be dehydrating so there is water in them the astronauts can drink. They also act as body armor, protecting the wearer from some of the debris floating around space.

Spacesuits can’t protect you from everything

So you’ve got your suit, and you’ve promised not to leave the spaceship. Nothing will happen now, right? Not exactly. Scott’s list of ailments from his time in space included muscle and bone loss as well as an increase in pressure on his brain. Furthermore, his skin suffered from rashes and hives. A lack of gravity can result in the bodily fluids usually kept in place by gravity to work their way up the body to where they shouldn’t be. This fluid movement can cause swelling and high blood pressure.

Science is our future

Scott responded to a survey that found 4 out of 10 people believed their lives wouldn’t be any different without science. Something that truly shocked Scott. Scott thinks science is what will allow us to overcome the challenges that face all of humanity in the future, the growing population and the issues that comes with it. He thinks science is a great opportunity for children to get involved in finding ways to help the planet in the future.

The book that changed his life

Scott Kelly attributes reading one book to changing his whole life. He wasn’t the best student in the past, he admits, but found a way to achieve greatness thanks to the inspiration gained from The Right Stuff by Tom Wolfe. The book details the efforts of pilots doing postwar research for the U.S. with high powered experimental aircraft. It also documents some stories of the first selection process of NASA astronauts. Scott claims this book inspired him to become, firstly, a pilot and, secondly, an astronaut.

What was it like coming back to Earth?

Scott described his journey from space back to Earth as the wildest ride of his life. He describes the experience of hurtling toward the Earth’s surface as like going over Niagara Falls in a barrel, but while on fire. After spending a year in space, Scott was surprised how long he felt his year took to complete, claiming it is a really, really long time. He said the first time he breathed fresh air after they opened the hatch of his pod was like his first ever breath of air, as though he had been born again.

Space is the fountain of youth?

On the ISS they circle the Earth sixteen times a day, which means they get to witness 16 sunrises every day. During his time on the ISS, Scott orbited the Earth 5,440 times. It would be fair to say Scott has seen a lot of the Earth from the rare viewpoint of space. Tests showed his chromosomes actually appeared to get younger. This meant that for a while his body was younger than his twin brother’s, although they returned to normal when he got back to Earth.

Deep pockets are required

Scott believes space and science is the future for humanity but worries that certain barriers are preventing science from helping as much as it could. He understands that a lot of the reasons why science is unable to prevail is not an issue with the scientists but rather the funding they are able to receive. Scott notes that it is more of a political issue regarding the funding of scientific research, but he believes that if humans can make their way to Mars, then they truly can do anything.