Astronaut Scott Kelly's One Year Mission and the Twin Study

The longest American space voyage ever is now over and scientists are about to swarm over Scott Kelly. When the astronaut touched down yesterday in Kazakhstan, he set a record for the longest spaceflight by an American. Kelly now holds the record of 340 days in space… and comparison with his twin brother, former astronaut Mark Kelly, offers a unique opportunity. We hear what's in store for Kelly and from America's former record holder.

Two thumbs up from NASA Astronaut Scott Kelly, resting in a chair outside of the spacecraft just minutes

after he landed in Kazakhstan on Wednesday, March 2, 2016 (Bill Ingalls/NASA)

Astronaut twins Mark Kelly and Scott Kelly