US astronauts Barry Wilmore and Sunita Williams returned from a 9-month space mission, surprisingly sporting gray hair, sparking curiosity about the cause.

As NASA’s primary facility for astronaut training and recovery, the center is well-equipped to address the challenges astronauts face after long missions.

What exactly happens to the body in space and what are the risks? In space, astronauts are exposed to varied and increased levels of radiation that are different from those on Earth. Read on to know how it affects human body.