Dwarfed by space shuttle Discovery and with Earth's horizon and the blackness of space providing the backdrop for the scene, NASA astronauts Rick Mastracchio (right) and Clayton Anderson worked in Discovery's aft payload bay during the mission's third and final spacewalk. During the six-hour, 24-minute spacewalk, Mastracchio and Anderson hooked up fluid lines of the new 1,700-pound tank, retrieved some micrometeoroid shields from the Quest airlock's exterior, relocated a portable foot restraint and prepared cables on the Zenith 1 truss for a spare Space to Ground Ku-Band antenna, two chores required before space shuttle Atlantis' STS-132/ULF-4 mission in May. Image Credit: NASA