A return trip to the Moon

Fifty years ago this month, the Apollo 12 mission successfully transported a second crew to the Moon and back, just four months after the initial Moon landing. Richard Gordon, who piloted Yankee Clipper, the mission’s command and service module, took this picture of the lunar module Intrepid as it made its descent to Oceanus Procellarum, a vast expanse of dark basaltic rock.

Apollo 12 marked the start of a new phase for the Apollo program, from lunar landing to lunar exploration. For the exploratory missions to achieve their scientific objectives, though, it was important that the lunar modules be able to hit their preselected landing sites. Apollo 11 had overshot its target by 6 kilometers. The goal for Apollo 12 was to touch down within 1.6 kilometers of NASA’s Surveyor 3 probe, which had landed in April 1967. Astronauts Charles “Pete” Conrad and Alan Bean achieved that and more: Intrepid ended up a mere 163 meters from the probe, and they set up instruments that measured the Moon’s seismicity, solar-wind flux, and magnetic field. For more on the scientific legacy of the Apollo program, see the article by Brad Jolliff and Mark Robinson, Physics Today, July 2019, page 44 . (Image courtesy of NASA.)