Today marks 36 years since the Challenger explosion.
In 1986, the space shuttle Challenger broke apart 73 seconds into flight. Seven crew members were killed including Christa McAuliffe, who would have been the first teacher in space.
Yesterday, NASA honored fallen heroes, including those aboard the Challenger space shuttle, during its annual Day of Remembrance.
On Jan. 27 every year, the entire agency commemorates space missions that ended in tragedy.
