Results from NASA’s landmark Twins Study reveals some interesting, surprising and reassuring data.

An American astronaut experienced multiple biological changes in space but returned to normal – with some exceptions – after coming back to Earth, according to a study involving twin brothers that shed light on how space flight affects the human body.

Although space travel exposes astronauts to forms of radiation that are uncommon on Earth, and that are linked to cancers and heart problems, a U.S. study suggests this does not significantly shorten their lives.