Before Armstrong and Aldrin stepped out of the lunar module on July 20, 1969, Aldrin unstowed a small plastic container of wine and some bread. He had brought them to the moon from Webster Presbyterian church near Houston, where he was an elder. Aldrin had received permission from the Presbyterian church's general assembly to administer it to himself. In his book Magnificent Desolation he shares the message he then radioed to Nasa: "I would like to request a few moments of silence ... and 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."

He then ate and drank the elements. The surreal ceremony is described in an article by Aldrin in a 1970 copy of Guideposts magazine: "I poured the wine into the chalice our church had given me. 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."

He also read a section of the gospel of John. During it all, Armstrong, reportedly a deist, is said to have watched respectfully but without making any comment.

The story of the secret communion service only emerged after the mission. Aldrin had originally planned to share the event with the world over the radio. However, at the time Nasa was still reeling from a lawsuit filed by the firebrand atheist Madalyn Murray O'Hair, resulting in the ceremony never being broadcast. The founder of American Atheists and self-titled "most hated woman in America" had taken on Nasa, as well as many other public organisation. Most famously, she successfully fought mandatory school prayer and bible recitation in US public schools.

After the Apollo 8 crew had read out the Genesis creation account in orbit, O'Hair wanted a ban on Nasa astronauts practising religion on earth, in space or "around and about the moon" while on duty.