This Day in History:, Challenger Disaster.
January 28, 1986.
73 seconds after its 11:38 a.m. launch, 
NASA's space shuttle exploded, 
killing all seven crew members.
Among the crew was Christa McAuliffe, 
a 37-year-old high school social 
studies teacher from New Hampshire.
McAuliffe had won a 
competition that earned 
her a place on the Challenger.
Millions witnessed 
the tragedy on live television.
In the aftermath, President Ronald Reagan 
appointed a special commission to 
determine what went wrong with Challenger.
The investigation determined 
the disaster was caused by 
the failure of an “O-ring” seal 
due to cold weather.
It would be two 
years before NASA sent 
astronauts into space again