heart murmur a sound additional to the normal heart sounds, heard on auscultation of the heart. Many murmurs are of no significance (innocent, physiological murmurs), particularly in young children, or due to increased blood flow through the heart during exercise, or in pregnancy.
Columbia Space Shuttle Disaster. On February 1, 2003, the space shuttle Columbia was returning from its 28th mission when, 16 minutes to touchdown, the shuttle incinerated and broke apart over Texas. Communication between the Columbia crew and Mission Control captures the last moments of the flight.
The space shuttle Challenger was one of NASA's greatest triumphs. It was the second shuttle to reach space, in April 1983. It successfully completed nine milestone missions. But Challenger was also NASA's darkest tragedy. On its 10th launch, on Jan. 28, 1986, the shuttle exploded 73 seconds after liftoff, killing the seven crewmembers. The accident changed the space program forever.