Twin brothers and former NASA astronauts Mark and Scott Kelly have each flown four missions and were part of NASA's twin study to research the impact of spaceflight on the human body. Hours before ...

NEW YORK -- You would expect a trip to space to be transformative, but NASA says it can lead to permanent DNA changes. The space agency studied the DNA of twin astronauts Scott and Mark Kelly. Scott ...

Idenitcal twins Scott, right, and Mark Kelly were the test subjects for a NASA study on how long periods of spaceflight affect the human body, with Mark on Earth while Scott spent almost a year in the ...

He drew blood from his arms. He saved his urine. He played computer games to test his memory and reaction speed. He measured the shape of his eyes. Two hundred-and-forty miles below, Scott’s twin ...