Astronaut Scott Kelly (right) and former astronaut Mark Kelly (left) are identical twin brothers who have helped NASA explore what life in space does to the human body.
NASA and companies like SpaceX and Boeing are looking to the moon and Mars as exciting targets for astronaut exploration, if not permanent colonization.
However, we're only just beginning to understand what long-term life in space can do to human bodies.
Much of what scientists are learning comes from NASA's ongoing Twins Study: a research program involving former NASA astronaut Scott Kelly, who lived in space for nearly a year, and his identical twin brother, Mark, who lived on the ground at the same time.
The lack of gravity, higher radiation exposure, space-compatible diet, and other facts of life in orbit affected Scott's body in significant and surprising ways.
Here are nine biological oddities that researchers have found might happen to your body if you live in space for a long time.