Astronaut Steve Kelly's DNA differs from identical twin's after a year in space

Scott Kelly is no longer genetically the same as his brother Mark - after the Nasa astronaut spent a year in space. 

According to Nasa, Kelly was part of a twins study to figure out how a year in space affected the body. 

While 93% of Kelly's genes went back to normal after a few days back on Earth, the remaining 7% could spell longer term changes to his immune system, DNA repair, bone formation networks, hypoxia, and hypercapnia.

They didn't just test his genes - Kelly appears to be no less intelligent relative to his brother after a year in space, though he is physically a bit slower and less accurate, possibly because he had to readjust to Earth's gravity.

The research on Kelly and his one year mission into space is a stepping stone for a three-year mission to Mars.