during the launch of STS-107 fatally compromised the vehicle's thermal protection system. The loss of Columbia and its crew led to a refocusing of NASA's human exploration programs and led to the establishment of the Constellation program in 2005 and the eventual retirement of the Space Shuttle program in 2011. Numerous memorials and dedications were made to honor the crew following the disaster; the Columbia Memorial Space Center was opened as a national memorial for the accident, and the Columbia Hills in Mars' Gusev crater, which the Spirit rover explored, were named after the crew. The majority of Columbias recovered remains are stored at the Kennedy Space Center's Vehicle Assembly Building, though some pieces are on public display at the nearby Visitor Complex. History Construction began on Columbia in 1975 at Rockwell International's (formerly North American Aviation/North American Rockwell) principal assembly facility in Palmdale, California, a suburb of Los Angeles. Columbia was named after the American sloop Columbia Rediviva which, from 1787 to 1793, under the command of Captain Robert Gray, explored the US Pacific Northwest and became the first American vessel to circumnavigate the globe. It's also named after the command module of Apollo 11, the first crewed landing on another celestial body. Columbia was also the female symbol of the United States. After construction, the orbiter arrived at Kennedy Space Center on March 25, 1979, to prepare for its first launch. Columbia was originally scheduled to lift off in late 1979, however the launch date was delayed by problems with both the RS-25 engine and the thermal protection system (TPS). On March 19, 1981, during preparations for a ground test, workers were asphyxiated in Columbia's nitrogen-purged aft engine compartment, resulting in (variously reported) two or three fatalities. The first flight of Columbia (STS-1) was commanded by John Young, a veteran from the Gemini and Apollo programs who was the ninth person to walk on the Moon in 1972, and piloted by Robert Crippen, a rookie astronaut originally selected to fly on the military's Manned Orbital Laboratory (MOL) spacecraft, but transferred to NASA after its cancellation, and served as a support crew member for the Skylab and Apollo-Soyuz missions. Columbia spent 610 days in the Orbiter Processing Facility (OPF), another 35 days in the Vehicle Assembly Building (VAB), and 105 days on Pad 39A before finally lifting off. It was successfully launched on April 12, 1981, the 20th anniversary