Astronaut’s DNA Doesn’t Match Twin Brother’s After Spending Year In Space


Astronaut Scott Kelly now has different DNA to his identical twin after spending just a year in space, a new NASA study has revealed.

The groundbreaking study has shown how spending time in space permanently changes your genes.

NASA said its research is important in its preparations for a three-year mission to Mars in the 2030s.


After 340 days aboard the International Space Station, American astronaut Scott Kelly returned to Earth in March 2016.

Since his return, NASA has run a number of tests on Kelly to get a good understanding of what effects the mission had on his body.

They used his identical twin Mark, who remained on Earth, as a control subject. Their nearly identical genomes allowed for an unprecedented look at the physical effects of long-term spaceflight.

Blood and other biological samples were collected from both of them before, during, and after Kelly’s mission.

While 93 per cent of Kelly’s genes returned to normal shortly after returning home, seven per cent were permanently altered.

These long-term changes have affected genes related to the immune system, DNA repair, bone formation, and how Scott’s tissue absorbs oxygen and carbon dioxide.


A principal investigator on the NASA twins study and an associate professor at Weill Cornell Medical College, told Business Insider:

When he went up into space it was like fireworks of gene expression.

But the changes that seem to have stuck around include changes in immune system function and retinal function related to his eye health.

Kelly said he was surprised by the change in his DNA, he said to Marketplace:

I did read in the newspaper the other day… that 7 percent of my DNA had changed permanently.

And I’m reading that, I’m like, ‘Huh, well that’s weird.’

You know, every day we walk out of our house. We’re exposing ourselves to risk … you decide the risk of driving to work is worth it because you have to get to work. My work just happened to be in space.


Scientists suggest the changes are the result of the extreme stress that Kelly’s body was subject to during his stay on the ISS.

When the body encounters something foreign, an immune response can be activated.

Dr Christopher Mason, a Twins Study researcher and an associate professor at Weill Cornell Medical College told Business Insider:

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.

NASA released its preliminary findings from the Twin Study last year, but has now released the results of a number of new studies.

The height difference was caused by the ISS’ microgravity conditions which elongate the spine, but the effect was only temporary.