NASA to commemorate three space tragedies

NASA will commemorate three space tragedies this week, which also marks the 25th anniversary of the shuttle Challenger accident that killed seven astronauts. The space agency will also pause to remember the 2003 loss of the shuttle Columbia and its crew and the earlier Apollo 1 fire that killed three astronauts.

URL: http://www.msnbc.msn.com/id/41238399/ns/technology_and_science-space/