NASA/TIME&LIFE/Getty Images Apollo 11 astronaut Buzz Aldrin standing on moon, with astronaut Neil Armstrong & lunar module reflected in helmet visor, during his historic first walk on the lunar surface.

The date, July 20, 1969, will forever be known as the day the United States of America put the first man on the moon. What most people do not know is the date also marks when Edwin “Buzz” Aldrin celebrated the first and only Lord’s Supper on the moon, a fact the U.S. government refused to make public at the time.

Inside the lunar module, just hours before stepping onto the moon for the first time, Aldrin radioed Houston Space Center Mission Control. He asked for a few moments of silence “to invite each person listening in, wherever and whomever they may be, to pause for a moment and contemplate the events of the past few hours, and to give thanks in his or her own way.”

In that moment of silence that followed, Aldrin silently read a passage from the book of John that he had written out on a 3×5 card: “I am the vine, you are the branches. Whoever remains in me, and I in him, will bear much fruit; for you can do nothing without me.” Then he took out the miniature chalice and bread and wine from his personal allowance pouch. “I poured the wine into the chalice our church had given me,” he told Guideposts magazine in 1970. “In the one-sixth gravity of the moon the wine curled slowly and gracefully up the side of the cup. It was interesting to think that the very first liquid ever poured on the moon, and the first food eaten there, were communion elements.” Neil Armstrong, the other astronaut onboard, did not participate.

But that was not Aldrin’s original plan—he had wanted to celebrate communion on the air with the rest of his comments, and the National Aeronautics and Space Administration (NASA) was not happy about it. Just months earlier, the Apollo 8 astronauts broadcast parts of the Biblical creation narrative from the book of Genesis while orbiting the moon on Christmas Eve: “In the beginning God created the heaven and the earth. And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters. And God said, Let there be light: and there was light.” Atheist Madalyn Murray O’Hair sued, arguing that the astronauts were government employees and therefore their actions violated the separation of church and state. The Supreme Court dismissed the case—for lack of jurisdiction—but it created enough of a stir that NASA wanted to avoid any such distractions from their missions. When Aldrin, a devout Presbyterian, told NASA flight operations coordinator Deke Slayton of his plan to celebrate communion during the live broadcast, Slayton told him to stand down. “No, that’s not a good idea, Buzz,” Slayton told him, according to Adrin’s memoir Magnificent Desolation. “Go ahead and have communion, but keep your comments more general.”

Aldrin later questioned his own decision to celebrate the Christian practice. “Perhaps if I had it to do over again, I would not choose to celebrate communion,” he wrote in his memoir. “Although it was a deeply meaningful experience for me, it was a Christian sacrament, and we had come to the moon in the name of all mankind—be they Christians, Jews, Muslims, animists, agnostics, or atheists. But at the time I could think of no better way to acknowledge the enormity of the Apollo 11 experience than by giving thanks to God.”

Webster Presbyterian Church—Aldrin’s church in Houston that supplied him with the bread and the wine for the unique occasion—still celebrates the lunar communion every year on the Sunday closest to July 20.