News flash: The heart produces urine
In an attempt to explain why astronaut Heidemarie Stefanyshyn-Piper fainted during a welcome ceremony, ABC News reported
The heart of an average person on Earth pumps blood throughout the body. But when an astronaut is in space, Levine explained, the blood remains predominantly in their chest cavity. Because of this, he said, the heart tries to get rid of excess blood through urination.