The International Space Station is seen through the centerline camera inside the Space Shuttle Endeavour's docking port as the two spacecraft separate after undocking in this image from NASA TV May 29, 2011. [Photo/Agencies]

Space Shuttle Endeavour astronaut Mike Fincke appears to have a clown nose as he plays with a water bubble in microgravity aboard the International Space Station in this image from NASA TV May 29, 2011. [Photo/Agencies]