Apollo 17

• 1. Introduction

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  Apollo 17 launched at 12:33 a.m. Eastern Standard Time on the 7th of December 1972, blazing into the night sky above Florida. Approximately 500,000 people stood near Kennedy Space Center to watch. The light from the Saturn V rocket was visible 800 kilometers away, and observers in Miami reported a red streak crossing the northern sky. It was the only crewed Saturn V launch to happen at night, and it would be the last.

  On board were Commander Gene Cernan, Command Module Pilot Ronald Evans, and Lunar Module Pilot Harrison Schmitt. Schmitt carried something none of the ten men who had walked on the Moon before him possessed: a doctorate in geology from Harvard University. He was the first and only professional scientist to reach the lunar surface.

  The mission set records in nearly every measurable category. Its crew spent 75 hours on the lunar surface, drove their rover 35.7 kilometers, and returned approximately 115 kilograms of lunar samples. Evans spent more time orbiting the Moon than any other individual in history.

  What drove the choice of crew, the choice of landing site, and the science they chased? And what did they find at a crater called Shorty that sent scientists at Mission Control into a frenzy of excitement?

• 2. The Crew Question

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  Gene Cernan crashed a Bell 47G helicopter into the Indian River near Cape Kennedy in January 1971, and that accident nearly cost him the mission of a lifetime. The crash was attributed to pilot error. Jim McDivitt, manager of the Apollo Spacecraft Program Office, objected to Cernan's selection as commander. Deke Slayton, NASA's director of flight crew operations, dismissed the concern and chose Cernan anyway.

  The standard Apollo crew rotation typically placed a backup crew in the prime crew slot three missions later. Cernan and Ronald Evans had backed up Apollo 14, which put them in line for Apollo 17. But the question of who would fill the lunar module pilot seat was not straightforward.

  Harrison Schmitt had backed up Apollo 15 and would ordinarily have flown on Apollo 18. When Apollo 18 was cancelled in September 1970, the scientific community pressed NASA to send a trained geologist rather than a pilot with informal geology training. NASA reassigned Schmitt to Apollo 17 as lunar module pilot. Cernan lobbied for Joe Engle, the former X-15 pilot who had trained with him, but was told Schmitt would fly with or without Cernan's endorsement. Cernan agreed.

  The backup crew carried its own complication. The original backups were the Apollo 15 crew: David Scott, Alfred Worden, and James Irwin. In May 1972, all three were removed because of their involvement in the Apollo 15 postal covers incident. Their replacements were John Young and Charles Duke from Apollo 16, along with Stuart Roosa from Apollo 14. Ken Mattingly, Apollo 16's command module pilot, declined the backup assignment so he could spend time with his newborn son, and moved to the Space Shuttle program instead.

  The prime crew was publicly announced on the 13th of August 1971. Cernan was 38 years old, a Navy captain who had flown on Gemini 9A and served as lunar module pilot of Apollo 10. Evans was 39, a Navy lieutenant commander on his first spaceflight. Schmitt, a civilian, was 37 and also flying for the first time.

• 3. Choosing Taurus-Littrow

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  Mission planners had two scientific goals that shaped every landing-site decision for Apollo 17: collect highland material older than what had been retrieved from Mare Imbrium, and investigate the possibility of relatively recent volcanic activity on the Moon.

  Several sites were eliminated before the final three were considered. A landing inside the crater Copernicus was ruled out because Apollo 12 had already sampled material from that impact. The lunar highlands near Tycho were rejected because the terrain was too rough for safe operations. A site in the far-side crater Tsiolkovskiy was dismissed on technical and cost grounds. A region southwest of Mare Crisium was dropped partly because a Soviet spacecraft could easily have reached it first; the Soviet Luna 20 probe ultimately did retrieve samples from that area shortly after the Apollo 17 site was chosen.

  Schmitt himself pushed for a far-side landing until Christopher C. Kraft, director of flight operations, told him plainly that NASA lacked the funds for the communications satellites that would have made it possible.

  The three finalists were Alphonsus crater, Gassendi crater, and the Taurus-Littrow valley. Gassendi was eliminated because its central peak would be difficult to reach. Alphonsus was judged operationally easier than Taurus-Littrow but of lesser scientific interest. A decisive factor in Taurus-Littrow's favor was that Al Worden, the command module pilot of Apollo 15, had overflown the valley and described formations he believed were volcanic in nature.

  The Apollo Site Selection Board voted unanimously for Taurus-Littrow at its final meeting in February 1972. At the site, planners believed the crew could gather old highland material from the remnant of a landslide on the valley's south wall, and also investigate evidence of younger explosive volcanic activity. A key criterion was also minimal overlap with the ground tracks of Apollo 15 and Apollo 16, so that new orbital data could be gathered.

• 4. Science on the Surface

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  At 6:54 p.m. Eastern Standard Time on the 11th of December, Cernan stepped off the ladder and became the first person to set foot on the Moon during Apollo 17. His first public words dedicated the step to everyone who had made the mission possible. Schmitt followed him down.

  Their equipment included the third Lunar Roving Vehicle to fly in the Apollo program. Over three moonwalks, the rover traveled a cumulative 35.7 kilometers in approximately four hours and twenty-six minutes of driving. Cernan always drove; Schmitt served as navigator and passenger. The farthest point from the lunar module reached 7.6 kilometers, a distance that remains the greatest any person has ever traveled from a pressurized spacecraft on a planetary body during any kind of extravehicular activity.

  The most dramatic discovery came at Shorty crater, during the second moonwalk. Schmitt spotted orange soil. Scientists at Mission Control were electrified, suspecting the crew had found an active volcanic vent. Post-mission analysis would show that Shorty was actually an impact crater, not a vent. The orange material turned out to be extremely small beads of volcanic glass formed about 3.5 billion years ago, remnants of a lava fountain that sprayed molten material high into the lunar sky early in the Moon's history. The impact that created Shorty exposed them less than 20 million years ago.

  The crew also deployed the Apollo Lunar Surface Experiments Package, which for Apollo 17 included five new instruments: the Heat Flow Experiment, the Lunar Surface Gravimeter, the Lunar Atmospheric Composition Experiment, the Lunar Seismic Profiling Experiment, and the Lunar Ejecta and Meteorites Experiment. The gravimeter was designed to detect gravity waves that would support Einstein's general theory of relativity, but it failed to function as intended. The atmospheric experiment used a mass spectrometer and identified principally neon, helium, and hydrogen in the lunar atmosphere. All powered ALSEP experiments were deactivated on the 30th of September 1977, primarily because of budget constraints.

  A 2.4 meter long, 2 centimeter diameter Lunar Neutron Probe was inserted into a drilled hole during the first moonwalk and retrieved during the third. Its measurements, combined with core sample data, contributed to current theories that the top centimeter of lunar regolith turns over every million years, while gardening to a depth of one meter takes roughly a billion years.

• 5. The Geology Beneath the Boots

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  Harrison Schmitt had, in effect, been running the geological mission from the lunar surface. That assessment came from William R. Muehlberger, one of the scientists who trained the crew. Muehlberger noted that Schmitt's field reports directly shaped what the science team in the geology backroom transmitted back up to the crew as tasks at each station. The top leadership at NASA knew it too, Muehlberger said, and raised no objection.

  The samples collected across three moonwalks totaled approximately 115 kilograms. The most significant individual specimen from the third excursion was designated Sample 76535, a troctolite gathered at geology station 6 near the base of the North Massif. Scientists later identified it as the oldest known unshocked lunar rock, meaning it has not been damaged by high-impact geological events. Researchers have used it in thermochronological studies to examine whether the Moon formed a metallic core or, as the results suggest, a core dynamo.

  The largest single rock brought back from the mission was Sample 70215, a fine-grained specimen Schmitt had noticed earlier and balanced on its edge. He retrieved it before closing out the final moonwalk. At 17.7 pounds, it is one of the few Moon rocks that members of the public may touch; a small piece is on exhibit at the Smithsonian Institution.

  Before leaving the surface, the crew collected a breccia rock dedicated to the nations of Earth. Seventy nations were represented by students visiting Mission Control in Houston at the time. Portions of that sample, called the Friendship Rock, were subsequently distributed to those nations.

  The Traverse Gravimeter Experiment, carried only on Apollo 17 and built by Draper Laboratory at the Massachusetts Institute of Technology, took 26 gravity measurements across the mission's three traverses. The Surface Electrical Properties experiment, also unique to Apollo 17, transmitted electrical signals from a ground antenna through the lunar soil to a receiver mounted on the rover. Results showed that to a depth of 2 kilometers, there is almost no water in the region where Apollo 17 landed.

• 6. Evans Alone in Orbit

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  Ronald Evans spent approximately 148 hours in lunar orbit, more time than any other individual has orbited the Moon. For most of that time, he was alone in the Command Module America while Cernan and Schmitt worked below.

  His schedule was dense. He operated the Scientific Instrument Module bay in the service module, which housed a lunar sounder, an infrared scanning radiometer, a far-ultraviolet spectrometer, a mapping camera, a panoramic camera, and a laser altimeter. He photographed geologic targets including the craters Eratosthenes and Copernicus and the vicinity of Mare Orientale, using Earthlight to illuminate surfaces not yet in sunlight. According to the Apollo 17 Mission Report, he captured all assigned scientific photographic targets plus additional targets of interest.

  Evans also reported seeing light flashes apparently originating from the lunar surface, what are called transient lunar phenomena. He observed these in the vicinity of Grimaldi crater and Mare Orientale, both known locations of interior outgassing. The causes of these phenomena remain poorly understood.

  Not everything went smoothly. Evans was so busy that he overslept one morning by an hour despite Mission Control's efforts to wake him. Before Cernan and Schmitt had descended to the surface, he misplaced his scissors, needed to open food packets. His crewmates lent him a pair of theirs.

  On the return trip to Earth, Evans conducted a 65-minute spacewalk to retrieve film cassettes from the service module's SIM bay, with Schmitt assisting from the hatch. At approximately 160,000 nautical miles from Earth, it was the third deep-space extravehicular activity in history. It was also the last EVA of the Apollo program.

• 7. Last Steps, Long Shadow

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  Before climbing into the lunar module for the final time, Cernan paused on the surface at Taurus-Littrow and spoke. He said that America's challenge of today had forged man's destiny of tomorrow, and closed with "Godspeed the crew of Apollo 17." He then followed Schmitt inside. The date was the 13th of December 1972.

  The spacecraft splashed down in the Pacific Ocean at 2:25 p.m. Eastern Standard Time on the 19th of December, 6.4 kilometers from the recovery ship. Commander Edward E. Dahill III piloted the recovery helicopter. All three astronauts were aboard the recovery ship 52 minutes after splashdown.

  None of the three flew in space again. Cernan retired from NASA and the Navy in 1976 and died in 2017. Evans retired from the Navy in 1976, left NASA in 1977, and died in 1990. Schmitt resigned from NASA in 1975, won a United States Senate seat from New Mexico in 1976, and served one six-year term.

  The Command Module America is now on permanent display at Space Center Houston at the Lyndon B. Johnson Space Center. The descent stage of Lunar Module Challenger remains at the Taurus-Littrow landing site on the Moon. A 2023 study of data from the Lunar Seismic Profiling Experiment found that the descent stage is still causing very slight tremors each lunar morning as its components expand in the heat.

  Apollo 17 held the distinction of being the last human flight beyond low Earth orbit until April 2026, when the Artemis II mission made its lunar flyby. In 2026, declassified records included an Apollo 17 photograph showing three dots in a triangular formation in the lunar sky. The Pentagon stated there was no consensus about the nature of the anomaly, though a preliminary analysis indicated it could be a physical object.