NASA selected the Descartes Highlands as Apollo 16’s landing site to sample the Moon’s ancient highlands. Before the mission, some scientists expected the area might include volcanic rocks, so the site was a test of competing ideas about lunar history.
Apollo 16 launched from Kennedy Space Center’s Launch Complex 39A with John Young, Ken Mattingly, and Charles Duke. It was the second of the extended “J missions,” designed for longer stays on the Moon and more intensive scientific work.
On the way to the Moon, Apollo 16 received an erroneous guidance signal suggesting a serious orientation problem. Mission controllers and the crew used a software change and procedures to ignore the false input, allowing the mission to continue safely toward lunar orbit.
After arriving at the Moon, engineers investigated oscillations linked to a backup circuit on the Command and Service Module’s main engine system. Because that engine was needed for critical maneuvers, the analysis delayed the lunar module landing while NASA confirmed the mission could proceed.
Young and Duke landed the Lunar Module Orion in the Descartes region of the lunar highlands, beginning Apollo 16’s surface operations. The landing was several hours later than planned, and the mission was shortened by about a day due to spacecraft concerns.
On the first moonwalk, the crew set up the Lunar Roving Vehicle and deployed the Apollo Lunar Surface Experiments Package (ALSEP). ALSEP was a set of instruments left on the Moon to transmit long-term scientific measurements back to Earth.
During ALSEP work, John Young accidentally pulled loose the Heat Flow Experiment cable. That ended this part of the planned investigation, which was meant to measure how much heat was escaping from the Moon’s interior at the landing site.
On the second EVA, Young and Duke drove the rover to multiple stops to collect rocks and soil and to document the terrain with photographs. They also used a portable magnetometer to measure local magnetic properties, helping scientists interpret the Moon’s crustal history.
During surface traverses near Station 1, the crew collected lunar sample 61016, nicknamed “Big Muley.” At about 11.7 kg, it became the largest single rock returned from the Moon, and it helped scientists study impact processes in the highlands.
After about three days on the Moon, the crew launched the lunar module ascent stage to rejoin Mattingly in lunar orbit. Docking reunited the crew and transferred samples and film for the trip back to Earth.
Apollo 16 released a small Particles and Fields subsatellite into lunar orbit to measure the plasma, particles, magnetic environment, and variations in lunar gravity. Because of constraints linked to the mission’s engine concerns, its orbit was lower than planned, shortening its operating life.
On the return trip to Earth, Ken Mattingly conducted a spacewalk to retrieve film cassettes from cameras mounted in the Service Module. This ensured high-value scientific imagery—such as mapping and panoramic photography—could be brought back for analysis.
Apollo 16 returned safely to Earth with astronauts, film, and nearly 96 kg of lunar samples. Post-mission analysis showed many returned rocks were impact breccias rather than the hoped-for volcanic materials, changing how scientists interpreted the Descartes Highlands and the Moon’s crust.
Apollo 16 (1972): Lunar Highlands Exploration and Scientific Program