Moments before astronaut Neil Armstrong steered a lunar module onto the surface of the moon, Charlie Duke wondered if he might have to abort one of the most spectacular missions of the 20th century.

While Armstrong hovered over the gray expanse, Duke was a quarter-million miles away, tucked behind a bank of computers at Apollo Mission Control Center in Houston. Duke was the capsule communicator (CAPCOM) for this phase of the mission. With a headset and a microphone, his job was to shepherd Armstrong and fellow astronaut Edwin “Buzz” Aldrin onto the moon without catastrophe.

And Duke was worried.

As they descended, the astronauts were off course and headed toward a field of boulders. They began piloting the module to another landing spot, but that meant burning critical fuel supply. Duke had about 30 seconds to decide whether to call off the landing.

In mission control, scores of NASA engineers in skinny ties and pocket protectors fell nearly silent until they heard Armstrong’s voice: “Houston, Tranquility Base here. The Eagle has landed.”

The moment was literally breathtaking.

“Roger, Tranquility,” Duke replied. “We copy you on the ground. You’ve got a bunch of guys about to turn blue. We’re breathing again. Thanks a lot.” Duke says he meant it: He held his breath for the final few moments before the astronauts became the first men in history to touch down on another world.

For Duke, the greatest adventures were still ahead. He would go on to pilot the lunar module for the Apollo 16 mission in 1972 and become the youngest astronaut to walk on the moon at age 36. (He stills grins when he talks about zooming up lunar hills in a moon buggy known as the lunar rover.)

Still, despite the grand odyssey in a rocket to the moon, Duke says the most important moment came a few years later in his car on a highway near New Braunfels, Texas. After years of post-Apollo turmoil, Duke turned to his wife, Dotty, and said in his Southern drawl, “Darling, there’s no doubt in my mind that Jesus Christ is the Son of God.”

This summer, July 20th marks the 50th anniversary of the Apollo 11 mission that captivated millions of people and broadcast Armstrong’s famous words: “That’s one small step for man—one giant leap for mankind.”

Astronauts and astronomers hope remembrances of Apollo 11—and the eight other lunar missions in the Apollo program—ignite fresh interest in scientific careers and space exploration, even as private companies aspire to build space colonies or travel to Mars.

Duke hopes the awe-inspiring footage and images will also spark the kind of spiritual wonder he finally embraced years after his own voyage to the moon. Though he didn’t recognize it then, he marvels at it now when he remembers what he saw in space: “The heavens declare the glory of God.”