"It is the worst disaster in the history of the American space program." Forty years ago on January 28, 1986, the space shuttle Challenger exploded 73 seconds after liftoff from Cape Canaveral, killing all seven crew members, including school teacher Christa McAuliffe from New Hampshire, who had won a national competition to become the first teacher in space. Peter Jennings anchored ABC's World News Tonight from Washington, with John Quiñones leading off the broadcast's coverage. | ABC World New

35 YEARS LATER: On this day in 1986, the Space Shuttle Challenger exploded after liftoff, killing all seven astronauts on board. The Challenger broke apart at 11:39 a.m., falling into the Atlantic Ocean. Investigators would later discover the disaster was caused by the failure of an “O ring” seal in one of the two solid-fuel rockets. As a result of the horrific accident, NASA did not send astronauts into space for more than two years as it redesigned a number of space shuttle features for improv