Hundreds of people have attended a memorial ceremony at the Kennedy Space Center in Florida marking the 25th anniversary of the explosion of the U.S. space shuttle "Challenger."
Seven astronauts were killed on January 28, 1986, when a booster engine failed just 73 seconds after launch, causing "Challenger" to explode.
Those killed included Christa McAuliffe, an American schoolteacher who was supposed to become the first nonprofessional astronaut to travel into space.
June Scobee Rodgers, widow of "Challenger" Commander Dick Scobee, remembered watching the explosion in a speech at the memorial.
"We were stunned to see the unspeakable unfold right before our eyes," she said. "Could this really happen? No one believed it could happen. What should have been a day heralded for education turned to tragedy in a split second. Our loved ones were gone. A nation grieved and our future looked uncertain."
The memorial on January 28 was held just months before the U.S. space agency NASA is due to formally shut down the 30-year-old shuttle program due to high operating costs.
The shuttle fleet is to be retired after three more planned flights this year to the International Space Station.
compiled from agency reports