NASA astronauts Alan Poindexter and James P. Dutton Jr. pose for a photo under space shuttle Discovery.

At the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida, NASA astronauts Alan Poindexter (right) and James P. Dutton Jr., STS-131 commander and pilot, respectively, pose for a photo under space shuttle Discovery. Discovery landed on Runway 33 after 15 days in space, completing the more than 6.2-million-mile STS-131 mission on orbit 238. Main gear touchdown was at 9:08:35 a.m. (EDT) on April 20, 2010, followed by nose gear touchdown at 9:08:47 a.m. and wheelstop at 9:09:33 a.m. The seven-member STS-131 crew carried the Leonardo Multi-Purpose Logistics Module, filled with supplies, a new crew sleeping quarters and science racks that were transferred to the International Space Station's laboratories. The crew also switched out a gyroscope on the station?s truss, installed a spare ammonia storage tank and retrieved a Japanese experiment from the station?s exterior. STS-131 is the 33rd shuttle mission to the station and the 131st shuttle mission overall.