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Mark and Scott Kelly at the Johnson Space Center

NASA’s Twin Study reports changes in human body during spaceflight

Spending a year on the space station has a great impact on the human body but the normal body functions get restored after returning to Earth. Human beings were not evolved to be able to float in microgravity or to survive under the influence of radiation levels in space.

NASA astronaut, Scott Kelly spent almost an year on International Space Station in a mission launched in 2015. His body was subjected to incredible stress, accumulation of fluids in upper body and head led to the swelling of these parts, his genes were activated in unusual ways and his immune system went to overdrive compared to his identical twin brother, Mark Kelly. Both the brothers have been in space, but Mark remained on Earth during Scott’s mission. As time passed, Scott experienced reduced body mass, genome instability, major swelling in his blood vessels, shifts in metabolism and changes in his microbiome and also a increase in the length of telomeres.

A group of ten teams were working on NASA‘s Twin Study which included 84 researchers from 12 universities. They followed the brother duo, during and after the flight got over and tracked the change in the bodies of the brothers over the entire course of the study. Though the scope of the research was limited, this data will be very valuable when scientists plan to send astronauts on long duration spaceflights.


Because of the small sample size, there was no interest in the Twins’ Study for many years after both of them got selected as astronauts in 1996. But after Scott Kelly’s record breaking stay in space station, the discussion gathered steam and a proper study was undertaken whose full report will be soon published. Mike Snyder, the head of genetics at Stanford University and a co-author of the Twins’ Study said that this will be the first in-depth study of the people in space at a biochemical level.

A lot of interesting changes have been noticed in the twins’ genes. There are no changes in the DNA, but there have been changes in the genes which are activated to synthesize proteins. Researchers did not compare the genes of the brothers directly but rather compared the changes in the genes’ expression. As soon as Scott went into space, there was a huge shift in the over 1000 genes which change dynamically. This shows the response of the body to a completely different environment.

The most curious finding was that of the lengthening of telomeres. Telomeres are the chromosome ends which shorten as we get older. Although the telomeres returned to the same average length on his return to Earth.

The integrated report from the Twins Study researchers was released in the Science journal.

About the author: Kalpit Veerwal
Kalpit Veerwal is a second year Computer Science undergraduate at IIT Bombay. He is well known for being the only person to score 360/360 in JEE (Main). He is registered in the Limca Book of Records for the same. A blogger in his free time, he has also secured top ranks in various exams held in India and the world.

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