Wreckage of the doomed Space Shuttle Challenger found

The shuttle exploded 73 seconds after take off from Cape Kennedy Space Centre on January 26 1986.
The 20 foot piece of wreckage was found on the ocean floor off Florida .
All seven crew members died, including schoolteacher Christa McAuliffe.
Investigations blamed the disaster on compromised O-ring seals on an external fuel tank which hardened due to unusually cold temperatures.