One of the simplest and most haunting photographs ever made was taken on July 20, 1969, when astronaut Neil Armstrong stepped off the Apollo 11’s lunar module and placed his left foot on the surface of the moon. It was Richard Underwood, NASA’s chief of photography in the 1960s, who taught the astronauts how to expose, frame, and focus their shots. “Your key to immortality,” he said to motivate them, “is in the quality of your photographs and nothing else.” The images they captured—on six missions over the course of a three-year period—ranged from work-a-day documentation to the extraordinary. And as more astronauts landed on and explored the moon’s surface, the more footsteps they left behind. What was startling and novel the first time it was photographed became a pictorial constant. In 2011, conspiracists who claimed that these pictures were faked were proven wrong when a NASA lunar orbiter captured the sharpest images of landing sites ever taken and revealed the astronauts’ footsteps to still be there and where, it is estimated, they will remain for at least a million years.