Scott Kelly's DNA Did Not Change Because of Space, NASA Confirms

We regret to inform you those widely circulated articles claiming astronaut Scott Kelly’s DNA changed after spending a year in space were incorrect, according to an official NASA statement shared Thursday with media outlets, including Inverse.

“Mark and Scott Kelly are still identical twins,” NASA Johnson Space Center News Chief Kelly O. Humphries says in an email to reporters. “Scott’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.”

On March 8, Business Insider published a story about preliminary findings from NASA’s ongoing Twins Study, published in a press release from January. The study analyzes Scott and Mark Kelly, who are both twins and astronauts. That is one true and accurate fact in the article.

“Another interesting finding concerned what some call the ‘space gene,’ which was alluded to in 2017,” NASA writes. “Researchers now know that 93 percent of Scott’s genes returned to normal after landing. However, the remaining 7 percent point to possible longer-term changes in genes related to his immune system, DNA repair, bone formation networks, hypoxia, and hypercapnia.”

Here’s where it gets messy from this statement: The Business Insider story claimed, “Roughly seven percent of Scott Kelly’s genes may have permanently changed as a result of his time in space.” The next day, Newsweek published a story about the same results with the headline “NASA Twins Study Confirms Astronaut’s DNA Actually Changed in Space.” The thing is, they’re both wrong, because neither NASA nor the researchers on the Twins Study ever said that.

Regardless, these stories made the rounds on social media and got picked up by numerous local news outlets across the country. Even Scott Kelly himself was bewildered.

After much confusion, NASA tried to set the record straight with reporters.

“The change related to only seven percent of the gene expression that changed during spaceflight that had not returned to preflight after six months on Earth,” Humphries explains in the same email shared with Inverse. “This change of gene expression is very minimal. We are at the beginning of our understanding of how space flight affects the molecular level of the human body. NASA and the other researchers collaborating on these studies expect to announce more comprehensive results on the twins studies this summer.”

Space travel impacted Kelly, sure, but not in the way the articles above describe. The way Kelly’s DNA is expressed changed after he spent an extended period of time in space, but that does not mean his DNA changed. This just means that spaceflight impacted Scott Kelly’s gene expression levels and the way his DNA is producing messenger RNA (mRNA), which in turn lets your body do pretty much everything it needs to do to survive.

Claiming that seven percent of his DNA changed is scientifically absurd. As Gizmodo’s Ryan Mandelbaum astutely notes:

“If seven percent of Scott Kelly’s DNA actually changed, he would be a completely different species. Humans and chimps, for example, share 96 percent of the same DNA, a 4 percent difference.”

Since space didn’t turn Scott Kelly into a golden retriever or a bonobo, I think it’s safe to say we can stop sharing articles that (pretty much) suggest he did.

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