No, space did not permanently alter 7 percent of Scott Kelly’s DNA
Several stories this week have proclaimed that the DNA of former NASA astronaut Scott Kelly changed during his year living on the International Space Station. The stories say that 7 percent of his genes did not return back to normal when he came back to Earth. It makes it seem as if the space environment permanently altered his genetic code. The problem? That’s not true.
The mistake stems from an inaccurate interpretation of NASA’s ongoing Twins Study. When Scott went to space in 2015, his identical twin Mark — also a former NASA astronaut — stayed on the ground. The idea was that Mark would serve as a control subject — a nearly identical genetic copy that NASA could use to figure out how the space environment changed Scott’s body.