The most famous shoe print in the world is not on this world at all. It’s on the moon, probably still there in the gray dust.

On July 20, 1969, the Apollo 11 astronaut Buzz Aldrin took a step forward, backed up, then took a photograph. What he left behind on the moon and captured for the rest of us on Earth remains remarkable in its simplicity and timeless in its evocation.

“Framed in the photo was evidence of man on the moon,” Mr. Aldrin later wrote in Magnificent Desolation. “A single footprint, showing in perfect detail a reverse mold of the treads from the bottom of my moon boot.”

Mr. Aldrin’s footprint is about an inch deep — enough to cast a shadow from the dim sunlight over his right shoulder. It is straight on the sides and rounded at the toes and the heel, the shape of a racetrack. It is filled with lines, like rungs of a ladder, formed by eight flat, straight-edged ribs.