Fast asleep in space

Astronauts Pam Melroy (left), George Zamka (bottom right), and Paolo Nespoli doze in their sleeping bags, which are secured on the middeck of the space shuttle Discovery while docked with the International Space Station.

Typically, astronauts are scheduled to get eight hours of sleep at the end of each mission day. Much like sleep on Earth, though, they may wake up in the middle of their sleep to use the toilet, or stay up late and look out the window. As when sleeping on Earth, astronauts may have dreams and nightmares, and even snore.