On January 28, 1986, nothing was supposed to be different. Space Shuttle Challenger, NASA's second Space Shuttle orbiter, had already completed nine missions after making its maiden flight nearly three years earlier; Challenger flew 85 percent of all Space Shuttle missions in 1983 and 1984 and became known as the workhouse of NASA's prized fleet. But 73 seconds after launch, which was broadcast live for the country to see, Challenger exploded. All seven crew members were killed and the entire shuttle fleet was grounded for more than two years while NASA engineers worked to figure out what went wrong. We know now that a booster failure resulted in the explosion that stunned a nation and cut mission STS 51-L short.

A quarter-century later, NASA continues to do important work, but the Space Shuttle system is scheduled to be retired from service later this year after 135 launches.

UPDATE: NASA has posted an interactive 'Day of Remembrance' feature on its website. Visit the site to read more about the seven crew members who lost their lives on Challenger's final mission. LIFE has put together a special tribute to Space Shuttle Challenger that includes a narrative of the events that unfolded twenty-five years ago today and a collection of stunning photographs. We've added some of those images, with permission, to the gallery above.

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