Today marks the 23rd anniversary of a terrible tragedy in the history of the Space Program: The Challenger disaster. On 28 January 1986, 7 astronauts lost their lives when Shuttle Challenger exploded just 73 seconds after launch. Mission Fact sheet here; Crew info here; Video here; Image collections here and here.

Mission STS-51L was the 25th Shuttle flight, and it carried the first "Teacher In Space", Christa McAuliffe. The Challenger, (OV-99), was the second orbiter built, and had completed 9 successful missions (starting with STS-6 in 1983) before the awful incident, which was caused by O-rings in the right solid rocket booster becoming brittle in the winter cold.

The accident rocked the nation and became embedded in the minds of an entire generation. The remains of some crewmembers were buried with honors at Arlington National Cemetery, and the wreckage of the spacecraft is sealed in a missile silo at Cape Canaveral. NASA grounded the Shuttle program for more than two years while safety improvements were made.

The Challenger Learning Centers, dedicated to space science education, were founded in honor of the crew. Remember the brave men and women of Challenger, Apollo 1, and Columbia!