Astronaut Scott Kellys current 12-month stay on the International Space Station is testing human limits for space travel and laying the groundwork for a manned mission to Mars. Despite the technological "comforts" of the International Space Station, a year in space has been described as the epitome of extreme, with extraordinarily high physical stakes. A Year in Space also follows retired astronaut Mark Kelly, Scotts identical twin brother. In the Kelly brothers, NASA has a near-perfect, two person sample group for biomedical research. NASA is closely tracking Scotts physical and emotional changes, and his biological functions, down to the molecular level while he is in orbit. The agency hopes to identify precisely what changes happened to Scott as a result of 12 months in space by comparing him to his identical twin, Mark, on Earth. The film tells the story of what it takes to spend a year in space and then, using what NASA has learned from the Kelly brothers, what it means for humanity as we journey to Mars and beyond. The immediate future of human space exploration rests on how Kelly functions in his year in space. For NASA, for Scott Kelly and his family, for the tantalizing prospect of human trip to Mars in our lifetime, the stakes of this expedition couldnt be higher. The documentary also delves into the broader historical context of the mission, including the history of space exploration, the political background of the Russian-U.S. relationshipScotts compatriot at the start of the mission is Russian astronaut Mikhail Korniyenkand the science and engineering conundrums posed by interplanetary space travel.