Editorial use only NASA astronaut Christa McAuliffe (1948-1986, centre) watching STS-61-A launch with fellow NASA astronaut Barbara Morgan (born 1951). McAuliffe was one of ten finalists in the NASA Teacher in Space Project. She was selected as a payload on the NASA shuttle Challenger mission 51-L, which exploded seventy three seconds after lift off on the 28th January 1986. All seven crew members were killed. It is thought that the accident was caused by a failure of an 0-ring in a seal on the right hand solid rocket booster, with consequent ignition of the leaking fuel. Morgan was the backup selected for McAuliffe on the STS-51L mission. She later became the first teacher in space.