On January 28, 1986, space shuttle Challenger broke apart 73 seconds into flight, killing all seven crewmembers on board. It was the first time NASA had lost astronauts during a spaceflight.

Few who were alive 25 years ago can forget that day, nor the iconic footage and photographs of the pale, corkscrewing plumes in the sky where Challenger had just been. The failure of a pressure seal in one of the two solid-fuel rocket boosters was later identified as the cause of the shuttle's breakup.

The disaster must have been especially personal for Charles Bolden, now NASA's chief, who was a member of the astronaut corps at the time. In fact, he had just concluded a shuttle mission 10 days prior to Challenger's launch in 1986. Bolden and NASA deputy administrator Lori Garver will honor the Challenger crew as part of NASA's annual Day of Remembrance by laying a wreath at Arlington National Cemetery in Virginia on the morning of January 27. Similar events are planned for Kennedy Space Center in Florida and Johnson Space Center in Houston.

The agency's Day of Remembrance honors those who perished in the Challenger accident as well as others who have lost their lives in pursuit of space exploration. This time of year is fraught with spaceflight tragedy—excluding automobile or aircraft crashes involving astronauts, all three of NASA's fatal accidents occurred at about the same time of year. On January 27, 1967, three astronauts were killed in the Apollo 1 command module when a fire broke out during a test on the launch pad. And on February 1, 2003, space shuttle Columbia broke apart over Texas as it was descending toward a landing, killing all seven crewmembers on board.

In addition to the Day of Remembrance events, a separate memorial for the Challenger astronauts will be held on the actual anniversary of the disaster, January 28, at Kennedy Space Center.

Photo of the 1986 Challenger disaster: NASA