A catastrophic failure occurred 73 seconds after liftoff as the shuttle emerged from “Max-Q,” the period of highest mechanical stress in the lower atmosphere. The vehicle broke apart in flight and exploded into a fireball. All seven aboard the shuttle were killed, and searches revealed no sign of the crew.

(CNN) - Wednesday marks the 40th anniversary of the Challenger space shuttle explosion. It was a moment of collective grief on Jan. 28, 1986, when the space shuttle exploded during a live broadcast.

NASA's Space Shuttle Challenger lifted off 40 years ago with six astronauts and a teacher on board. That legacy is being carried on by those on Earth all those years later.

🚀 On This Day — 28 Jan In 1986, the Challenger shuttle tragically disintegrated shortly after launch, claiming the lives of seven astronauts. This disaster reshaped our views on spaceflight safety and exploration. #NITheCS #ScienceHistory #SpaceExploration pic.twitter.com/slHHwVrf3n

Forty years after the Challenger disaster, NPR explores the engineers' last-minute efforts to stop the launch, their decades of guilt and the vital lessons that remain critical for NASA today.

It was Jan. 28, 1986 when seven crew members loaded onto the Challenger space shuttle on Florida's Space Coast, with plans to head to space. Instead, the shuttle exploded minutes after launching – killing all seven people on board: Christa McAuliffe,