On May 28, 1967, Maurice Lavan­oux read an article in the New York Times Magazine with the headline ­after apollo, a colony on the moon. The author—Isaac Asimov—explained how such a thing could happen: by constructing residential caverns beneath the moon’s surface, settlers could create a livable climate powered by solar energy. “Merely reaching the moon is no end in itself,” Asimov wrote. “Having reached it, cannot we and the Soviets and any other nation that cares to join the venture combine to explore it, develop it and make it a home for man?” Lavanoux was titillated; this confirmed what he had learned a few years earlier, while judging an oral presentation by a Princeton architectural student: that lunar colonization was not only possible but imminent. (The student, William R. Sims, went on to design parts of Epcot Center.) Lavanoux was the secretary of the Liturgical Arts Society and the editor of Liturgical Arts, a quarterly journal dealing with the arts of the Catholic Church. Emboldened by his findings, he decided that if there was to be a colony on the moon, there should certainly be a chapel, and if there was to be a chapel, he would be the one to build it.

Lavanoux already had an architect in mind—a man named Mark Mills, who had spoken to him of a “dream church” he hoped to build someday. Based on his interest in the Princeton ­thesis, Lavanoux had written a letter to Mills telling him that he’d been contemplating the idea of a chapel on the moon. “Your dream church might well be on the same wavelength,” he wrote. After reading Asi­mov’s article, he wrote to Mills again, telling him that the upcoming issue of Liturgical Arts would be devoted to the idea of a lunar chapel and asking him to draw up blueprints. “There are so few who can see ahead, with vision and imagination!” he told Mills. A few months later, Mills sent back a design for a teepee-like underground structure walled with translucent plastic. At its apex, a solar eye would poke up through the moon’s crust, allowing worshippers to gaze up at the stars.

Around the same time, Lavanoux met a young composer named Johannes Somary. They were both members of the Quilisma Club, a group of Gregorian-chant enthusiasts who met and sang at an apartment in midtown Manhattan. (A quilisma is a musical notation used in Gregorian chant.) Impressed by Somary’s compositions for the group, Lavanoux wrote to Somary...