NASA's Twin Study Just Proved Space Has Deeper Effects on DNA Than Thought

Approximately 7 percent of Scott Kelly's DNA did not return back to 'normal' after returning home, NASA recently confirmed.
Shelby Rogers

The Kelly brothers might be the most famous pair of twins in aeronautics right now. The popular NASA Twins Study revealed another discovery thanks to the long-term observations of Scott Kelly's health compared to his brother Mark. 

Scott Kelly spent 340 days aboard the International Space Station between 2015 and 2016. That time spent on the ISS is the record for the longest single flight of an American. Not only did his time in space give astronauts a new record, but it gave NASA a perfect opportunity to understand how the human body reacts to nearly a year in space. 

In addition to Kelly's extensive time in space, there's also the benefit of him being a twin. Mark Kelly also flew as an astronaut for the space program. Mark remained grounded during Scott's flight, and NASA gathered data about the earth-bound Kelly brother while the other was on the ISS. 

NASA researchers most recently discovered that while Mark and Scott Kelly are still identical twins, Scott's DNA reacted to space in a unique way. Scott's telomeres -- the ends of chromosomes that shorten as people get older -- lengthened in space. This information was originally discovered last year; however, NASA confirmed the findings just a few weeks ago after noticing that Scott's telomeres shortened after he landed. 

There was also additional findings regarding about the "space gene," originally hinted at in the 2017 discoveries. Only 93 percent of Scott's genes returned to normal after landing. That unaccounted for 7 percent? It could be a clue for possible long-term changes brought on by space that deal with his immune system, DNA repair, and bone networks. NASA made it clear in a secondary statement that "the change related to only 7 percent of the gene expression that changed during spaceflight that had not returned to preflight after six months on Earth." All in all, NASA said, the gene expression change was minimal. However, it does give researchers further insights into how the body reacts to space. 

"The Twins Study has benefited NASA by providing the first application of genomics to evaluate potential risks to the human body in space," NASA said in a statement. "The NASA Twins Study also presented a unique opportunity for investigators to collaborate, participating in a team approach to HRP research."


The Human Research Program's mission is to discover and create better ways to keep astronauts safe while in space. The HRP uses a variety of data gathering techniques -- including tracking astronaut's physiological changes both before and after their flights. 

For Scott, most of the changes experienced returned to their former state as his body readjusted to Earth's gravity once again. According to NASA, most of those changes happened in just a few hours after returning. However, other elements took months to return to 'normal.'

"We are at the beginning of our understanding of how spaceflight affects the molecular level of the human body," NASA said in its press release. "NASA and the other researchers collaborating on these studies expect to announce more comprehensive results on the twins studies this summer."



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