The U.S. space shuttle Atlantis is returning to Earth after spending a week at the International Space Station to deliver tons of spare parts to the orbiting outpost. Atlantis undocked from the space station yesterday and is due to land in the southeastern U.S. state of Florida tomorrow. Atlantis is bringing seven astronauts back to Earth, including Nicole Stott, who left the space station on Tuesday after spending three months in orbit. Canadian astronaut Robert Thirsk said advancements made during the Atlantis mission will contribute to a bright future for space exploration. U.S. space agency NASA plans to retire its shuttle fleet next year after several more missions to upgrade the station.<br/>