Identical Twins No Longer Identical After Year Long Trip To Space? (Apparently Not)

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Update: There have been some articles challenging this story, including a report from The Verge in which Nichole Holm said: “The two are still very much identical twins,” she continued “They possessed different mutations before and after the flight, and Scott experienced different changes in his RNA, not DNA. But their DNA is still nearly identical and much more similar to each other than to any other person on earth (or in space).”

NASA also shared a statement sayingScott’s DNA did not fundamentally change,” “What researchers did observe are changes in gene expression, which is how your body reacts to your environment. This likely is within the range for humans under stress, such as mountain climbing or SCUBA diving.”

However, there have also been some incredible results coming from the experiment. Firstly  Scott’s gut bacteria did change significantly. He also did experience unusual genetic changes, with the protective caps (known as telomeres) on the ends of his DNA strands increasing while in space.


Scott Kelly just returned to earth after 340 days in space, on return he had grown 2 inches and had a different genetic code to his brother.

Scott and Mark Kelly are identical twins, or at least they they used to be. Scott Kelly just returned from a 340-day adventure on the International Space Station (ISS) on return to Earth they found some interesting changes.

Scott had grown by 2 inches, he had a reduced body mass and the bacteria in his gut had completely changed. According to latest findings from NASA researchers his DNA has significantly changed.

A NASA statement has suggests that the stress of being in space may have activated hundreds of “space genes” which can alterer an astronaut’s immune system, as well as other bodily functions. While the majority of Kelly’s changes have returned to normal, around 7 percent remained altered.

The changes are “thought to be from the stresses of space travel, which can cause changes in a cell’s biological pathways,” the NASA statement said. “Such actions can trigger the assembly of new molecules, like a fat or protein, cellular degradation, and can turn genes on and off, which change cellular function.”

The twins are part of a study named  the Twins Study, which is aiming to share some of the the long-term side-effects of space travel on the human body. In March 2015 Scott entered the ISS for what would be the longest single space trip ever taken at 340 days.

Mark, Scott’s identical twin (also an astronaut), remained Earthbound as the counterpart of the study. The brothers are the only identical astronaut twins in history, NASA said. This gives a very interesting scope to work with as identical twins are born with matching DNA, meaning, the Kelly brothers made a great before-and-after comparison.

Researchers mapped out physical and mental health changes before, during and after the year Scott spent in space. Most of Scott’s physical changes proved to be temporary, including the 2-inch in height gained. However, the genes involved in bone formation, immune system responses, oxygen deprivation and DNA repair have still not returned.  NASA reports, this could be a complex reaction due to a strange type of space stress.

Christopher Mason, a Twins Study researcher and an associate professor at Weill Cornell Medical College, told Business Insider “Oftentimes, when the body encounters something foreign, an immune response is activated,” he continued “The body thinks there’s a reason to defend itself. We know there are aspects of being in space that are not a pleasant experience, and this is the molecular manifestation of the body responding to that stress.”

Part of the motivation behind these studies are to understanding “space genes” and how they react to longer space missions. This will play a crucial role in planning longer manned missions, such as the 3 year mission to Mars.

Image credit NASA

I am Luke Miller the author of this article, and creator of Potential For Change. I like to blend psychology and spirituality to help you create more happiness in your life.Grab a copy of my free 33 Page Illustrated eBook- Psychology Meets Spirituality- Secrets To A Supercharged Life You Control Here

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