The U.S. space agency, NASA, has marked the 20th anniversary of the Challenger space shuttle tragedy that killed seven astronauts.
The ceremony was held Saturday at the Kennedy Space Center in Cape Canaveral, Florida, where the Challenger was launched January 28, 1986.
The widow of the shuttle's commander joined a top NASA official in laying a wreath at a memorial that bears the names of the seven astronauts and other fallen space explorers.
The Challenger exploded 73 seconds after taking off under clear blue skies in near freezing temperatures. Those on board included Christa McAuliffe, who was to be the first school teacher in space.
The explosion, which was seen on live television and before an audience that included school children, was blamed on a failure of a seal in the shuttle's solid rocket booster due to the cold weather.
Some information for this reoport provided by AP and AFP.