On Dec. 17, 1972, American astronaut Eugene Cernan paused to look up at Earth. At over 240,000 miles away it was small enough to be blotted out by an outstretched thumb. A few moments later he would enter the lunar lander, close the hatch and blast off to begin Apollo 17’s journey back to Earth. Cernan was the last person to leave footprints on the moon. Since then, humans have never ventured farther than 240 miles from Earth’s surface, let alone return to its only natural satellite.

History has come to judge the Apollo program as a freak alignment of science, politics and popular will—a one-off and ultimately one-way ticket to the moon. Dreams of establishing a permanent base on the lunar surface and then colonizing Mars are now retold through black-and-white footage of men with white shirts and crew cuts manning mission-control consoles, or bravely striding across launch pads in silver pressure suits. ...