What happens to an astronaut's body during a year in space

NASA astronaut and Russian cosmonaut Mikhail Kornienko are halfway through the year they are spending in space. Above is a NASA chart with some fun facts about what Kelly will experience.

“I think the legacy of this mission will be based on the science of having us in space for a year,” Kelly said. “The great data we collected, what we learned about being in space for this long and how that will help our journey to Mars someday.”

Below, NASA's mini-documentary "A Year In Space" narrated by Lando, er, Billy Dee Williams:

https://youtu.be/BWbqTdj5hRg