How a Year in Space Affects Your Biology

Jillian Barton

The One-Year Mission by NASA consisted of a nearly year-long stay at the International Space Station beginning in March 2015 by astronaut Scott Kelly. It was the longest space mission by an American astronaut. Also known as the NASA Twins Study, the purpose of this extended stay was to examine the long-term health effects of space on the human body. While Scott Kelly spent 340 days in space undergoing extensive testing, his identical twin brother, Mark Kelly, stayed on Earth, serving as a control subject to which they could compare Scott’s data.

Identical twins provide a unique opportunity for researchers to examine the effects of stress from space travel on the human body because they have nearly identical genomes. Furthermore, the Kelly twins have experienced similar environments. Both Scott and Mark Kelly are astronauts – Scott Kelly having a lifetime total of 520 days in space, and Mark Kelly having a lifetime total of 54 days in space. Due to these reasons, their life experiences are extremely similar, providing NASA researchers with an unprecedented opportunity.

The Twins Study is a part of NASA’s Human Research Program focused on determining the best methods to support safe space travel. The study includes ten research teams who analyzed samples from the twins that were taken before, during, and after the mission. Specifically, NASA researchers examined the human body on physiological, behavioral, microbiological, and molecular levels to determine how space may change different organs, perception and reasoning, decision making, organisms in the gut, and gene expression.

NASA to Launch Sequel to Successful Lightning Study Mission Image Credit: NASA’s Marshall Space Flight Center

The initial findings of the NASA Twin Study released in January are providing scientists with an interesting first look at how space travel can manipulate many of the body’s systems.

On a biological level, researchers observed a decrease in bone formation during the second half of Kelly’s mission. This was expected, as the decrease in mechanical strain on the skeletal system in space leads to progressive bone loss. Researchers also found that Scott’s immune response remained unchanged in space. His body responded similarly in space to a flu injection.

Scott also grew two inches in space, yet, since his return in March 2016, he has returned to his normal height. Scientists believe this is because in a zero-G environment like the International Space Station, the spine stretches, unlike on Earth where gravity keeps the spine in place by constantly pushing it together.

Kelly’s cognitive performance was also examined, showing his speed and accuracy decreasing in space. He also suffered from impaired short distance vision in his eyes, and his bodily fluids redistributed around his body, often causing congestion and headaches.

#TBT: ATLAS-1 Launches to Conduct Space Science — March 24, 1992 Image Credit: NASA’s Marshall Space Flight Center

But one finding in particular is baffling scientists. While Kelly was in space, his telomeres lengthened. Telomeres are the end caps of chromosomes that protect the chromosome from deterioration and fusing with others. Telomeres are known to shorten as we age and are exposed to stress. Because he was aging and put under the heavy stressors of space, researchers hypothesized that his telomeres would shorten. But they did the exact opposite, and scientists are still not sure why. Once Kelly returned to Earth, the length of his telomeres returned to their pre-flight lengths. In order to further understand how space affects telomere length, scientists are running a separate study examining ten different astronauts that will be done in 2018 and will hopefully clarify Kelly’s results.

Although much more analysis of the results needs to be done, the Twins Study results have begun to reveal just how the human body is altered due to the stress of space. A full report of the results is expected to be released later this year.

Space is an extremely stressful environment both mentally and physically. Inside the International Space Station, astronauts are at an increased risk for cancer due to the elevated radiation levels. Astronauts often suffer from space motion sickness, bone density loss, vision impairments, immune system weaknesses, and other ailments. That is why NASA is supporting this study and future endeavors to further understand the effects of space on the human body. If it were not for Scott and Mark Kelly’s bravery to risk their lives for this study, we would not be one step closer to understanding the cost on the human body of a six-month journey to Mars.

Feature Image Credit: NASA’s Marshall Space Flight Center 

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