Astronaut Scott Kelly's DNA changed in space and his identical twin proves it

Space exploration is a small part "let’s see if we can do this," and a large part l"et’s find out what we learn if we do this and that." Astronaut Scott Kelly’s record-breaking time spent in orbit around the planet Earth gave him an unique human experience.  Spending almost two years in space changed the way Kelly thought about our planet and it changed him down to his DNA—literally. Comparing him with his identical twin proves it.