ARI SHAPIRO, HOST:
Now for a story about an astronaut who is not a space mutant.
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DANIEL HUOT: And liftoff.
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UNIDENTIFIED WOMAN: Scott Kelly blasted into orbit to begin his record-setting 340-day mission.
SHAPIRO: While Scott Kelly spent a year in space in 2015, his twin brother Mark stayed on Earth.
SARAH MCCAMMON, HOST:
Throughout that year and since Scott's been back, scientists have been comparing the two.
CHRISTOPHER MASON: So we had multiple kinds of samples that were collected, including whole blood cells, saliva. We took skin samples.
MCCAMMON: That's Christopher Mason from Weill Cornell Medicine. He's recently come out with an analysis of all those samples showing one effect of Scott's year in outer space.
MASON: We saw some genes that were activated while he was in space. It looked like actually they maintained their activation state even six months after he'd been back on Earth.
SHAPIRO: Mason says genes change all the time - when you climb a mountain or scuba dive or run a marathon. What's important is which changes space seems to have made on Scott Kelly's body.
MASON: We observed changes relative to immune system response. So it looked as if he was actually dealing with the stress of spaceflight and his immune system was on high alert. We also saw changes with DNA repair, so his body actually dealing with some of the impacts of radiation. And then also we saw genes involved in bone and muscle formation.
SHAPIRO: This information could give scientists a few clues about the long-term impact of space travel as NASA begins to plan missions to Mars.
MASON: We need to know what the body does during these long periods in zero gravity. And how does it respond? We can try and either fix it or prevent anything that's too stressful to the body from happening in the first place.
MCCAMMON: Now, there's been a little bit of misinformation about this study. Scott is still Mark Kelly's identical twin. And he did not have 7 percent of his genes altered by space travel.
MASON: If 7 percent of your DNA change, you would potentially even be a different species.
MCCAMMON: So again, he's not a space mutant.
MASON: As far as we know, he does not have any particularly special powers, although he has a lot of endurance and he's very strong and otherwise is quite healthy.
SHAPIRO: He's just a regular guy with space genes.
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