Earlier this morning astronaut Scott Kelly arrived in Houston after nearly a year-long mission in space. The one-year mission was designed to help NASA better understand what happens to an astronaut's physical and mental health during an extremely long stay in a micro-gravity environment. Kelly's results will be compared to his identical twin brother Mark who was basically the control subject on earth.

There is one thing that NASA has already learned from his record breaking time in space and that is the fact that he's two inches taller than his brother Mark. There is obviously still a lot research and study which according to CNBC, includes looking out for brittle bones, weak muscles, puffy face and legs, smaller heart, balance issues, messed up body clock and more.