An astronaut who spent a year in space now has seven percent of his DNA different to that of his identical twin. Scott and Mark Kelly were part of an experiment into the effects of space travel as part of planning for Mars trips.

Scott (pictured right) spent a year on the International Space Station, giving double benefits to the study. Firstly, previous research has been based on six-month stints, so this was a step closer to learning about the effects of a Mars trip, which would likely have to be three years including travel there and back to be worthwhile. Secondly, Mark remained on Earth as the perfect control subject.

Researchers had already published the results of initial findings on the physical and psychological effects on Scott. Now they’ve detailed analysis on the long-term effects on his DNA. 93 percent of his genes are now back to normal, but the remaining seven percent remain altered and suggest long-term changes.

The genetic changes appear largely related to the differing physical demands of space travel. The genes in question relate to:

• bone formation;
• DNA repair;
• hypercapnia (excessive carbon dioxide in the blood);
• hypoxia (insufficient oxygen supplies to tissue); and
• the immune system.

The researchers also revealed that Scott’s speed and accuracy upon returning to Earth decreased by a greater degree than normally happens after a six-month space flight. However, they couldn’t rule out if the result was affected by the Astronaut having a busier schedule than usual after his return to Earth.