It has now been 50 years since astronauts last launched to the moon.
NASA's Apollo 17 mission lifted off on Dec. 7, 1972, sending Gene Cernan, Harrison Schmitt and Ronald Evans toward Earth's nearest neighbor. The trio arrived in orbit around the moon three days later.
Evans remained in lunar orbit aboard the mission's command module, named America. Cernan and Schmitt took the lunar module Challenger to the surface, touching down on the southeastern rim of the moon's Mare Serenitatis ("Sea of Serenity") on Dec. 11.
Related: Facts about NASA's Apollo program
Schmitt, a geologist, became the first scientist ever to walk on the moon. He and Cernan spent a record-setting 75 hours on the lunar surface. During that time, the duo set up or performed 10 different scientific experiments, snapped more than 2,000 photos and collected 243 pounds (110 kilograms) of soil and rock to bring home to Earth, according to a NASA mission description (opens in new tab). That sample haul included a 4.2 billion-year-old stone whose characteristics suggest that the moon once had a global magnetic field, as Earth still does.
Cernan and Schmitt knew they'd be the last-ever Apollo moonwalkers, as NASA was beginning to shift its focus toward long-term crewed stays in Earth orbit. So, before Challenger lifted off from the lunar surface on Dec. 14, the two astronauts revealed a plaque affixed to the module. It read: "Here man completed his first exploration of the moon, December 1972 A.D. May the spirit of peace in which he came be reflected in the lives of all mankind."
We won't have to wait much longer for the next crewed moon landing, if all goes according to NASA's plan. The agency aims to put boots down near the lunar south pole in 2025 or 2026, on the third mission of its Artemis program, which is named after the sister of Apollo in Greek mythology.
That timeline is dependent on the first two Artemis missions going well. Artemis 2 is scheduled to launch astronauts around the moon in 2024. Artemis 1 is currently underway; it launched an uncrewed Orion capsule atop a Space Launch System (SLS) rocket on Nov. 16.
The SLS performed well that day, and Orion has been notching milestones like clockwork. The capsule arrived in lunar orbit on Nov. 25, departed on Dec. 1 and began heading back toward Earth via an engine burn during a close flyby of the moon on Monday (Dec. 5).
Orion is scheduled to splash down in the Pacific Ocean off the California coast on Dec. 11 — the same day that Cernan and Schmitt landed in the Mare Serenitatis. The Apollo 17 mission's splashdown came eight days after that lunar landing; Cernan, Schmitt and Evans returned to Earth on Dec. 19, 1972.
Mike Wall is the author of "Out There (opens in new tab)" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall (opens in new tab). Follow us on Twitter @Spacedotcom (opens in new tab) or on Facebook (opens in new tab).