Earlier this afternoon, NASA postponed the launch of the space shuttle Endeavor, citing problems with heaters in the auxiliary power unit. The shuttle launch has been closely followed in the news, both because recovering congresswoman Gabrielle Giffords is seeing off her husband, astronaut Mark Kelly, and because this mission is the second-to-last in the shuttle program's history, and for the foreseeable future of the American space program. And once Kelly and his companions blast into space, they face a whole new set of physical and biological changes.
For example, a 2001 study conducted by doctors at NASA, Harvard Medical School, and the University of California-San Diego found that space travel greatly adjusted astronauts' sleep patterns, even after they returned to Earth. Though astronauts were scheduled to sleep eight hours a day on both of the two missions studied, average sleep time was actually between six and six-and-a-half hours. The quality of the sleep also worsened, with more wakefulness during the final third of the sleep period. Finally, when astronauts returned to earth, rapid eye movement (REM) sleep, when most vivid dreaming occurs, "markedly increased." Hopefully, the Endeavor crew will at least have state-of-the-art memory foam.