Astronaut’s DNA no longer matches that of his identical twin, NASA finds

(WHDH) — Spending a year in space not only changes your outlook, it could change some of your genes.

NASA has learned astronaut Scott Kelly and his identical twin – astronaut Mark Kelly – are no longer genetically the same.

This was revealed in preliminary results from the space agency’s twins study.

According to researchers, seven percent of Scott’s genes did not return to normal after his return to earth two years ago.

They believe some of the gene mutations could have been caused by the stresses of space travel.

The twins study helps NASA gain insight into what happens to the human body in space beyond the usual six months on the International Space Station.

NASA says research like this is needed before astronauts are sent on journeys like a planned three-year mission to Mars.