Apollo 17
Eugene Cernan salutes the United States flag, with the Apollo Lunar Module Challenger and Lunar Roving Vehicle in the background
Mission typeCrewed lunar landing (J)
OperatorNASA
COSPAR ID
  • CSM: 1972-096A
  • LM: 1972-096C
SATCAT no.
  • CSM: 6300
  • LM: 6307
Mission duration12 days, 13 hours, 51 minutes, 59 seconds
Spacecraft properties
Spacecraft
Manufacturer
Launch mass48,607 kilograms (107,161 lb)
Landing mass5,500 kilograms (12,120 lb)
Crew
Crew size3
Members
Callsign
  • CSM: America
  • LM: Challenger
EVAs1 in cislunar space
Plus 3 on the lunar surface
EVA duration1 hour, 5 minutes, 44 seconds
Spacewalk to retrieve film cassettes
Start of mission
Launch dateDecember 7, 1972, 05:33:00 (1972-12-07UTC05:33Z) UTC (12:33 AM EST)[1]
RocketSaturn V SA-512
Launch siteKennedy LC-39A
End of mission
Recovered byUSS Ticonderoga
Landing dateDecember 19, 1972, 19:24:59 (1972-12-19UTC19:25:00Z) UTC[1]
Landing siteSouth Pacific Ocean
17°53′S 166°07′W / 17.88°S 166.11°W / -17.88; -166.11 (Apollo 17 splashdown)
Orbital parameters
Reference systemSelenocentric
Periselene altitude26.9 kilometers (14.5 nmi)
Aposelene altitude109.3 kilometers (59.0 nmi)
EpochDecember 11, 4:04 UTC
Lunar orbiter
Spacecraft componentCommand and service module
Orbital insertionDecember 10, 1972, 19:53:55 UTC[1]
Orbital departureDecember 16, 1972, 23:35:09 UTC[1]
Orbits75
Lunar lander
Spacecraft componentLunar module
Landing dateDecember 11, 1972, 19:54:58 UTC[1]
Return launchDecember 14, 1972, 22:54:37 UTC[1]
Landing siteTaurus–Littrow
20°11′27″N 30°46′18″E / 20.1908°N 30.7717°E / 20.1908; 30.7717[2]
Sample mass110.52 kilograms (243.7 lb)
Surface EVAs3
EVA duration
  • 22 hours, 3 minutes, 57 seconds
  • First: 7 hours, 11 minutes, 53 seconds
  • Second: 7 hours, 36 minutes, 56 seconds
  • Third: 7 hours, 15 minutes, 8 seconds
Lunar rover
Distance driven35.9 kilometers (22.3 mi)
Docking with LM
Docking dateDecember 7, 1972, 09:30:10 UTC[1]
Undocking dateDecember 11, 1972, 17:20:56 UTC[1]
Docking with LM Ascent Stage
Docking dateDecember 15, 1972, 01:10:15 UTC[1]
Undocking dateDecember 15, 1972, 04:51:31 UTC[1]
Payload
Mass
  • LRV: 210 kilograms (460 lb)[3]
Apollo 18 (canceled) →
 

Apollo 17 (December 7 – 19, 1972) was the final mission of NASA's Apollo program, the most recent time humans have set foot on the Moon or traveled beyond low Earth orbit. Commander Eugene Cernan and Lunar Module Pilot Harrison Schmitt walked on the Moon, while Command Module Pilot Ronald Evans orbited above. Schmitt was the only professional geologist to land on the Moon, selected in place of Joe Engle with NASA under pressure to send a scientist to the Moon. The mission's heavy emphasis on science meant the inclusion of a number of new experiments, including a biological experiment containing five mice carried in the command module.

Launched at 12:33 a.m. Eastern Standard Time (EST) on December 7, 1972, after the only launch-pad delay in the Apollo program, Apollo 17 was a "J-type" mission that included three days on the lunar surface, extended scientific capability, and the use of the third Lunar Roving Vehicle (LRV). Cernan and Schmitt landed in the Taurus–Littrow valley and completed three moonwalks, taking lunar samples and deploying scientific instruments. Mission planners considered two primary goals in selecting the landing site: to sample lunar highland material older than Mare Imbrium and to investigate the possibility of relatively recent volcanic activity. Evans remained in lunar orbit in the command and service module (CSM), taking scientific measurements and photographs. The spacecraft returned to Earth on December 19.

The mission broke several crewed spaceflight records, including the longest crewed lunar landing mission (12 days 14 hours),[4] greatest distance from a spacecraft during an EVA of any type (7.6 kilometers, a record which still stands), longest total lunar surface extravehicular activities (22 hours 4 minutes),[5] largest lunar sample return (110.52 kilograms or 243.7 lb), longest time in lunar orbit (6 days 4 hours),[4] and most lunar orbits (75).[6]

Crew and key Mission Control personnel

Position[7] Astronaut
Commander Eugene A. Cernan
Third and last spaceflight
Command Module Pilot Ronald E. Evans
Only spaceflight
Lunar Module Pilot Harrison H. Schmitt
Only spaceflight

In 1969, NASA announced[8] that the backup crew of Apollo 14 would be Eugene Cernan, Ronald Evans, and former X-15 pilot Joe Engle.[9] This put them in line to be prime crew of Apollo 17, as the Apollo program's crew rotation generally meant that a backup crew would fly as prime crew three missions later. Meanwhile, Harrison Schmitt, a professional geologist before becoming an astronaut, served on the backup crew of Apollo 15 and would be due to fly as Lunar Module Pilot on Apollo 18 as a result of the rotation.[10]

However, Apollo 18 was cancelled in September 1970. The scientific community pressed NASA to assign a geologist, rather than a pilot with non-professional geological training, to an Apollo landing. NASA subsequently assigned Schmitt to Apollo 17 as the Lunar Module Pilot. Schmitt's selection to the Apollo 17 crew left NASA Director of Flight Crew Operations Deke Slayton with the question of who would fill the two other Apollo 17 slots: the rest of the Apollo 15 backup crew (Dick Gordon and Vance Brand) or the Apollo 14 backup crew (except for Engle). Slayton ultimately chose Cernan and Evans,[8] though support for assigning Cernan to Apollo 17 was not unanimous within NASA. Cernan crashed a Bell 47G helicopter into the Indian River near Cape Canaveral during a training exercise in January 1971; the accident was later attributed to pilot error, as Cernan had misjudged his altitude before crashing into the water. Jim McDivitt, who was manager of the Apollo Spacecraft Program Office at the time, objected strongly to Cernan's selection and cited the accident, though Slayton dismissed the concern. After being offered command of the mission, Cernan objected to Engle's omission from the crew, but ultimately acquiesced to Schmitt's selection when it became clear that Schmitt would fly on Apollo 17 with or without Cernan, and the prime crew was set.[11][12] The prime crew of Apollo 17 was publicly announced on August 13, 1971.[13]

The flight crew of Apollo 17, Gene Cernan (seated), Harrison Schmitt (standing, left) and Ronald Evans
The flight crew of Apollo 17, Gene Cernan (seated), Harrison Schmitt (standing, left) and Ronald Evans

Cernan, a 38-year-old captain in the United States Navy at the time of Apollo 17, had been selected in the third group of astronauts in 1963. He flew as Pilot of Gemini 9A in 1966 and as Lunar Module Pilot of Apollo 10 in 1969 before his service on Apollo 14's backup crew. Evans, selected as part of the fifth group of astronauts in 1966, was 39 years old at the time of Apollo 17 and a lieutenant commander in the United States Navy. Schmitt, a civilian, was 37 years old at the time of Apollo 17. With a doctorate in geology from Harvard University, he had been selected in the fourth group of astronauts in 1965. Both Evans and Schmitt were making their first spaceflights.[14]

For Apollo 16 and 17, the final Apollo lunar missions, NASA selected backup crews consisting of astronauts who had already flown Apollo lunar missions, thus taking advantage of their experience. The alternative was to train astronauts as backup crew members who most likely would not have an opportunity to put their lunar mission training to use in-flight.[15] By using lunar veterans, NASA saved the time, money and effort which would be involved in training rookies for these dead-end positions.[16] The original backup crew for Apollo 17, announced at the same time as the prime crew,[13] was the crew of Apollo 15, David Scott as commander, Alfred Worden as CMP and James Irwin as LMP; however, they were removed because of their roles in the Apollo 15 postal covers incident.[17] On May 23, 1972, they were replaced with the landing crew of Apollo 16, John W. Young as backup crew commander and Charles Duke as LMP, and Apollo 14's CMP, Stuart Roosa.[14][18][19][20] Originally, Apollo 16's CMP, Ken Mattingly was to be assigned along with his crewmates, but he declined so he could spend more time with his family, his first son having just been born, and instead took an assignment to the Space Shuttle program.[21]

For Apollo, a third crew of astronauts, known as the support crew, was designated in addition to the prime and backup crews used on projects Mercury and Gemini. Slayton created the support crews because Jim McDivitt, who commanded Apollo 9, believed that, with preparation going on in facilities across the US, meetings that needed a member of the flight crew would be missed. Support crew members were to assist as directed by the mission commander.[22] Usually low in seniority, they assembled the mission's rules, flight plan, and checklists, and kept them updated;[23][24] For Apollo 17, they were Robert F. Overmyer, Robert A. Parker and C. Gordon Fullerton.[25]

Flight directors were Gerry Griffin, first shift, Gene Kranz and Neil B. Hutchinson, second shift, and Pete Frank and Charles R. Lewis, third shift.[26] Flight directors during Apollo had a one-sentence job description, "The flight director may take any actions necessary for crew safety and mission success."[27] Capsule communicators (CAPCOMs) were Fullerton, Parker, Young, Duke, Mattingly, Roosa, Alan Shepard and Joseph P. Allen.[28]

Mission insignia and call signs

The insignia's most prominent feature is an image of the Greek sun god Apollo backdropped by a rendering of an American eagle, the red bars on the eagle mirroring those on the flag of the United States. Three white stars above the red bars represent the three crewmembers of the mission. The background includes the Moon, the planet Saturn, and a galaxy or nebula. The wing of the eagle partially overlays the Moon, suggesting humanity's established presence there.[29]

Apollo 17 space-flown silver Robbins medallion
Apollo 17 space-flown silver Robbins medallion

The insignia includes, along with the colors of the U.S. flag (red, white, and blue), the color gold, representative of a "golden age" of spaceflight that was to begin with Apollo 17.[29] The image of Apollo in the mission insignia is a rendering of the Apollo Belvedere sculpture in the Vatican Museums. It looks forward into the future, towards the celestial objects shown in the insignia beyond the Moon. These represent humanity's goals, and the image symbolizes human intelligence, wisdom and ambition. The insignia was designed by Robert McCall, based on ideas from the crew.[30]

In deciding the call signs for the CM and LM, the crew wished to pay tribute to the American public for their support of the Apollo program, and to the mission, and wanted names with a tradition within American history. The CM was given the call sign "America". According to Cernan, this evoked the 19th century sailing ships which were given that name, and was a thank-you to the people of the United States. The crew selected the name "Challenger" for the LM in lieu of an alternative, "Heritage". Cernan stated that the selected name "just seemed to describe more of what the future for America really held, and that was a challenge".[31] After Schmitt stepped onto the Moon from Challenger, he stated, "I think the next generation ought to accept this as a challenge. Let's see them leave footprints like these."[32]

Planning and training

Scheduling and landing site selection

Initially, prior to the cancellation of Apollo 18 through 20, Apollo 17 was slated to launch in September 1971 as part of NASA's tentative launch schedule set forth in 1969.[33] The in-flight abort of Apollo 13 and the resulting modifications to the Apollo spacecraft delayed subsequent missions.[34] Additionally, following the cancellation of Apollo 20 in early 1970, NASA decided there would be no more than two Apollo missions per year.[35] Part of the reason Apollo 17 was scheduled for December 1972 was to make it fall after the presidential election in November, ensuring that if there was a disaster, it would have no effect on President Nixon's re-election campaign.[36] Nixon had been deeply concerned about the Apollo 13 astronauts, and, fearing another mission in crisis as he ran for re-election, initially decided to omit the funds for Apollo 17 from the budget; he was persuaded to accept a December 1972 date for the mission.[37]

Like Apollo 15 and Apollo 16, Apollo 17 was slated to be a "J-mission", an Apollo mission type that featured lunar surface stays of three days, higher scientific capability, and the usage of the Lunar Roving Vehicle. Since Apollo 17 was to be the final lunar landing of the Apollo program, high-priority landing sites that had not been visited previously were given consideration for potential exploration. Some sites were rejected at earlier stages. Thus, a landing in the crater Copernicus was rejected because Apollo 12 had already obtained samples from that impact, and three other Apollo expeditions had already visited the vicinity of Mare Imbrium, near the rim of which Copernicus is located. A landing in the lunar highlands near the crater Tycho was rejected because of the rough terrain that the astronauts would encounter there. A landing on the lunar far side in the crater Tsiolkovskiy was rejected due to technical considerations and the operational costs of maintaining communication with Earth during surface operations. A landing in a region southwest of Mare Crisium was rejected on the grounds that a Soviet spacecraft could easily access the site; Luna 20 ultimately did so shortly after the Apollo 17 site selection was made.[38] Schmitt advocated for a landing on the far side of the Moon until told by Director of Flight Operations Christopher C. Kraft that it would not happen as NASA lacked the funds for the necessary communications satellites.[39]

Landing site and surrounding area, as imaged from the Apollo 17 command module, 1972
Landing site and surrounding area, as imaged from the Apollo 17 command module, 1972

After the elimination of the above sites, three sites made the final consideration for Apollo 17: Alphonsus crater, Gassendi crater, and the Taurus-Littrow valley. In making the final landing site decision, mission planners took into consideration the primary objectives for Apollo 17: obtaining old highlands material from a substantial distance from Mare Imbrium, sampling material from young volcanic activity (i.e., less than three billion years), and having minimal ground overlap with the orbital ground tracks of Apollo 15 and Apollo 16 to maximize the amount of new data obtained.[38] A significant reason for the selection of Taurus-Littrow was that Apollo 15's CMP, Al Worden, had overflown the site and observed features he described as likely volcanic in nature.[40]

Gassendi was eliminated because NASA felt that its central peak would be difficult to reach due to the roughness of the local terrain, and, though Alphonsus might be easier operationally than Taurus-Littrow, it was of lesser scientific interest.[41] At Taurus-Littrow, it was believed that the crew would be able to obtain samples of old highland material from the remnants of a landslide event that occurred on the south wall of the valley and the possibility of relatively young, explosive volcanic activity in the area. Although the valley is similar to the landing site of Apollo 15 in that it is on the border of a lunar mare, the advantages of Taurus-Littrow were believed to outweigh the drawbacks.[38] On the unanimous recommendation of the Apollo Site Selection Board at its final meeting in February 1972, NASA selected Taurus-Littrow as the landing site for Apollo 17.[41]

Training

Gene Cernan participates in geology training in Sudbury, Ontario, in May 1972
Gene Cernan participates in geology training in Sudbury, Ontario, in May 1972

As with previous lunar landings, the Apollo 17 astronauts underwent an extensive training program that included learning to collect samples on the surface, usage of the spacesuits, navigation in the Lunar Roving Vehicle, field geology training, survival training, splashdown and recovery training, and equipment training.[42] The geology field trips were conducted as much as possible like the astronauts were on the Moon: they would be provided with overhead images and maps, and briefed on features of the site and a suggested routing. The following day, they would follow the route, and have tasks and observations to be done at each of the stops.[43]

The geology field trips began with one to Big Bend National Park in Texas in October 1971. The early ones were not specifically tailored to prepare the astronauts for Taurus-Littrow, which was not selected until February 1972, but by June, the astronauts were going on field trips to sites specifically selected to prepare for Apollo 17's landing site.[44] Both Cernan and Schmitt had served on backup crews for Apollo landing missions, and were familiar with many of the procedures. Their trainers, such as Gordon Swann, feared that Cernan would defer to Schmitt as a professional geologist on matters within his field. Cernan also had to adjust for the loss of Engle, with whom he had trained for Apollo 14. In spite of these issues, Cernan and Schmitt worked well together as a team, and Cernan became adept at describing what he was seeing on geology field trips, and working independently of Schmitt when necessary.[45]

The landing crew aimed for a division of labor so that, when they arrived in a new area, Cernan would perform tasks such as adjusting the antenna on the Lunar Roving Vehicle so as to transmit to Earth while Schmitt gave a report on the geological aspects of the site. This would allow the scientists in the geology "backroom" to adjust the tasks planned for that site, which would be transmitted to the CapCom and then to Cernan and Schmitt. According to William R. Muehlberger, one of the scientists who trained the astronauts, "In effect he [Schmitt] was running the mission from the Moon. But we set it up this way. All of those within the geological world certainly knew it, and I had a sneaking hunch that the top brass knew it too, but this is a practical way out, and they didn’t object."[46]

Also participating in some of the geology field trips were the commander and lunar module pilot of the backup crew. The initial field trips took place before the Apollo 15 astronauts were assigned as the backup crew for Apollo 17 in February 1972. Either one or both of David Scott and James Irwin of Apollo 15 took part in four field trips, though both were there only for two of them. After they were removed from the backup crew, the new backup commander and LMP, Young and Duke, took part in the final four field trips.[17] On field trips, the backup crew would follow half an hour after the prime crew, performing identical tasks, and have their own simulated CapCom and Mission Control guiding them.[43] The Apollo 17 astronauts had fourteen field trips—the Apollo 11 crew had only one.[47]

Evans did not go on the geology field trips, having his own set of trainers—by this time, geology training for the CMP was well-established. He would fly with a NASA geologist/pilot, Dick Laidley, over geologic features, with part of the exercise conducted at 40,000 feet (12,000 m), and part at 1,000 feet (300 m) to 5,000 feet (1,500 m). The higher altitude was equivalent to what could be seen from the planned lunar orbit of about 60 nmi with binoculars. Evans would be briefed for several hours before each exercise, and given study guides; afterwards, there would be debriefing and evaluation. Evans was trained regarding lunar geology by Farouk El-Baz late in the training cycle; this continued until close to launch. The CMP was given information regarding the lunar features he would overfly in the CSM and which he was expected to photograph.[48]

Mission hardware and experiments

SA-512, Apollo 17's Saturn V rocket, on the launch pad awaiting liftoff, November 1972
SA-512, Apollo 17's Saturn V rocket, on the launch pad awaiting liftoff, November 1972

Spacecraft and launch vehicle

The Apollo 17 spacecraft consisted of Command Module 114 (CM-114) and Service Module 114 (SM-114), together forming CSM-114, and Lunar Module 12 (LM-12), together with a Spacecraft-Lunar Module Adapter (SLA), numbered SLA-21, and a Launch Escape System (LES).[49][50][51] The LES contained a rocket motor that would propel the CM to safety in the event of an aborted mission in the moments after launch, while the SLA housed the LM during the launch and early part of the flight. The LES was jettisoned after the launch vehicle ascended to the point that it was not needed, while the SLA was left atop the S-IVB third stage of the rocket after the CSM and LM separated from it.[52][53]

The launch vehicle was a Saturn V, SA-512, the twelfth Saturn V to fly, and the tenth taking astronauts to orbit. It was similar to the earlier ones that had flown on every mission since Apollo 8.[54] With a weight at launch of 6,529,784 pounds (2,961,860 kg) (116,269 pounds (52,739 kg) of which was attributable to the spacecraft), Apollo 17's vehicle was slightly lighter than Apollo 16, but heavier than every other crewed Apollo mission.[55]

Preparation and assembly

The first piece of the launch vehicle to arrive at Kennedy Space Center was the S-II second stage, on October 27, 1970; it was followed by the S-IVB on December 21; the S-IC first stage did not arrive until May 11, 1972, followed by the Instrument Unit on June 7. By then, LM-12 had arrived, the ascent stage on June 16, 1971, and the descent stage the following day; they were not mated until May 18, 1972. CM-114, SM-114 and SLA-21 all arrived on March 24, 1972. The rover reached KSC on June 2, 1972.[56]

Cernan (seated, right) and Schmitt in the training LRV with the mockup LM in the background, August 1972
Cernan (seated, right) and Schmitt in the training LRV with the mockup LM in the background, August 1972

The CM and SM were mated on March 28, 1972,[56] and the testing of the spacecraft began that month.[57] The CSM was placed in a vacuum chamber at KSC, and the testing was conducted under those conditions. The LM was also placed in a vacuum chamber; both the prime and the backup crews participated in testing the CSM and LM.[58] During the testing, it was discovered that the LM's rendezvous radar assembly had received too much voltage during earlier tests; it was replaced by the manufacturer, Grumman. The LM's landing radar also gave trouble, locking up intermittently, and was also replaced. The LRV's front and rear steering motors also had to be replaced, and it required several modifications.[57] Following the July 1972 removal from the vacuum chamber, the LM's landing gear was installed, and it, the CSM and the SLA were mated to each other. The combined craft was moved into the Vehicle Assembly Building (VAB) in August for further testing, after which it was mounted on the launch vehicle.[58] After completing testing, including a simulated mission, the LRV was placed in the LM on August 13.[59]

Erection of the stages of the launch vehicle began on May 15, 1972, in High Bay 3 of the VAB, and was completed on June 27. Since the launch vehicles for Skylab 1 and Skylab 2 were being processed in the VAB at the same time, this marked the first time NASA had three launch vehicles there since the height of the Apollo program in 1969. After the spacecraft was mounted on the launch vehicle on August 24, it was rolled out to Pad 39-A on August 28.[59] Although this was not the final time a Saturn V would fly (another would lift Skylab to orbit), area residents reacted as though it was, and 5,000 of them watched the rollout, during which the prime crew joined the operating crew from Bendix atop the crawler.[57]

At Pad 39-A, testing continued, and the CSM was electrically mated to the launch vehicle on October 11, 1972. Testing concluded with the countdown demonstration tests, accomplished on November 20 and 21.[56] The countdown to launch began at 7:53 am (12:53 UTC) on December 5, 1972.[60]

Lunar surface science

ALSEP

The Apollo Lunar Surface Experiments Package was a suite of nuclear-powered experiments, flown on each landing mission after Apollo 11. This equipment was to be emplaced by the astronauts to continue functioning after the astronauts returned to Earth. All powered ALSEP experiments that remained active were deactivated on September 30, 1977,[61] principally because of budgetary constraints.[62] For Apollo 17, the ALSEP experiments were a Heat Flow Experiment (HFE), to measure the rate of heat loss from the interior of the Moon, a Lunar Surface Gravimeter (LSG), to measure precisely the lunar gravity field at the site, a Lunar Atmospheric Composition Experiment (LACE), to measure the composition of the thin lunar atmosphere, a Lunar Seismic Profiling Experiment (LSPE), to study the nature and physical properties of the nearby surface and subsurface areas, and a Lunar Ejecta and Meteorites Experiment (LEME), to measure the velocity and energy of dust particles.[63] Of these, only the HFE had been flown before; the others were new.[61]

The HFE had been flown on the aborted Apollo 13 mission, as well as on Apollo 15 and 16, but only placed successfully on Apollo 15, and unexpected results from that device made scientists anxious for a second successful emplacement. It was successfully deployed on Apollo 17.[64] The LSG, based on one widely used on Earth, was intended to detect gravity waves, something that would confirm Einstein's general theory of relativity;[65] it ultimately failed to function as intended.[66] The LACE was a surface-deployed module that used a mass spectrometer to analyse the Moon's atmosphere. To ensure it was unaffected by the LM's liftoff, it was heated to drive off contamination during the lunar night that followed, and only then was activated.[65] The LSPE was a seismic detecting device different from the seismometers emplaced on every landing from Apollo 12 to 16, as it used geophones, which would detect explosives to be set off by ground command once the astronauts left the Moon, as well as the impact of the jettisoned LM ascent stage, after which it would be deactivated.[67] It detected the liftoff of the ascent stage, as well as the explosives packages (one of which was observed via the television camera mounted on the LRV) and the ascent stage's impact.[68] The LEME had a set of detectors to measure the characteristics of the dust particles it sought; to protect it from the material which would be stirred up by the LM's liftoff, it had a cover that would be jettisoned by ground command after the astronauts left.[69]

Other lunar surface science

Apollo 17 Lunar Roving Vehicle as it was finally left parked on the Moon. The surface electrical properties (SEP) receiver is the antenna on the right-rear of the vehicle
Apollo 17 Lunar Roving Vehicle as it was finally left parked on the Moon. The surface electrical properties (SEP) receiver is the antenna on the right-rear of the vehicle

Apollo 17 was the third mission (the others being Apollo 15 and Apollo 16) to make use of a Lunar Roving Vehicle (LRV). In addition to being used by the astronauts for transport from station to station on the mission's three moonwalks, the LRV was used to transport the astronauts' tools, communications equipment, and the lunar samples they gathered.[70] The Apollo 17 LRV was also used to carry some of the scientific instruments, such as the Traverse Gravimeter Experiment (TGE) and Surface Electrical Properties (SEP) experiment.[66][71] The Apollo 17 LRV traveled a cumulative distance of approximately 35.9 km (22.3 mi) in a total drive time of about four hours and twenty-six minutes; the greatest distance Eugene Cernan and Harrison Schmitt traveled from the lunar module was about 7.6 km (4.7 mi).[3]

This was the only mission to carry the TGE, which was built by Draper Laboratory at the Massachusetts Institute of Technology. As gravimeters had proven to be useful in the geologic investigation of the Earth, the objective of this experiment was to determine the feasibility of using the same techniques on the Moon to learn about its internal structure. The gravimeter was used to obtain relative gravity measurements at the landing site in the immediate vicinity of the lunar module, as well as various locations on the mission's traverse routes. Scientists would then use this data to help determine the geological substructure of the landing site and the surrounding vicinity.[66] Measurements were taken while the TGE was mounted on the LRV, and also while the device was placed on the lunar surface.[72] A total of 26 measurements were taken with the TGE during the mission's three moonwalks, with productive results.[66]

The SEP was also unique to Apollo 17, and included two major components: a transmitting antenna deployed near the lunar module and a receiver mounted on the LRV. At different stops during the mission's traverses, electrical signals traveled from the transmitting device, through the ground, and were received at the LRV. The electrical properties of the lunar regolith could be determined by comparison of the transmitted and received electrical signals. The results of this experiment, which are consistent with lunar rock composition, show that there is almost no water in the area of the Moon in which Apollo 17 landed, to a depth of 2 km (1.2 mi).[71]

The Lunar Neutron Probe was a 2.4 m (7.9 ft) long, 2 cm (0.79 in) diameter probe to be inserted into one of the holes drilled into the surface to collect core samples. It measured the quantity of neutron flux found in the top 2 m (6.6 ft) of the lunar surface.[73] This was intended to measure the rate of the "gardening" process on the lunar surface, whereby the regolith on the surface is slowly mixed or buried due to micrometeorites and other events.[74] Placed during the first EVA, it was retrieved during the third and final EVA. The astronauts brought it with them back to Earth, and the measurements from it were compared with the evidence of neutron flux in the core that had been removed from the hole it had been placed in.[73] Results from the probe and from the cores were instrumental in current theories that the top centimeter of lunar regolith turns over every million years, whereas "gardening" to a depth of one meter takes about a billion years.[74]

Orbital science

Biological cosmic ray experiment

Main article: Fe, Fi, Fo, Fum, and Phooey

Apollo 17's CM carried a biological cosmic ray experiment (BIOCORE), containing five mice that had been implanted with radiation monitors under their scalps to see whether they suffered damage from cosmic rays.[75] These animals were placed in individual metal tubes inside a sealed container that had its own oxygen supply, and flown on the mission. All five were pocket mice (Perognathus longimembris); this species was chosen because it was well-documented, small, easy to maintain in an isolated state (not requiring drinking water for the duration of the mission and with highly concentrated waste), and for its ability to withstand environmental stress.[75] Officially, the mice—four male and one female—were assigned the identification numbers A3326, A3400, A3305, A3356 and A3352. Unofficially, according to Cernan, the Apollo 17 crew dubbed them Fe, Fi, Fo, Fum, and Phooey.[76]

Four of the five mice survived the flight, though only two of them appeared healthy and active; the cause of death of the fifth mouse was not determined. Of those that survived, the study found lesions in the scalp itself and liver. The scalp lesions and liver lesions appeared to be unrelated to one another, and were not thought to be the result of cosmic rays. No damage was found in the mice's retinas or viscera.[75] At the time of the publication of the Apollo 17 Preliminary Science Report, the mouse brains had not yet been examined.[75] However, subsequent studies showed no significant effect on the brains.[77]

Scientific instrument module

Apollo 17 SIM bay on the service module America, seen from the Lunar Module Challenger in orbit around the Moon
Apollo 17 SIM bay on the service module America, seen from the Lunar Module Challenger in orbit around the Moon

Sector one of the Apollo 17 SM contained the scientific instrument module (SIM) bay. The SIM bay housed three experiments for use in lunar orbit: a lunar sounder, an infrared scanning radiometer, and a far-ultraviolet spectrometer. A mapping camera, panoramic camera, and a laser altimeter were also included in the SIM bay.[78]

The lunar sounder beamed electromagnetic impulses toward the lunar surface, which were designed with the objective of obtaining data to assist in developing a geological model of the interior of the Moon to an approximate depth of 1.3 km (0.81 mi). The infrared scanning radiometer was designed with the objective of generating a temperature map of the lunar surface to aid in locating surface features such as rock fields, structural differences in the lunar crust, and volcanic activity. The far-ultraviolet spectrometer was to be used to obtain data pertaining to the composition, density, and constituency of the lunar atmosphere. The spectrometer was also designed to detect far-UV radiation emitted by the Sun that has been reflected off the lunar surface. The laser altimeter was designed with the intention of measuring the altitude of the spacecraft above the lunar surface within approximately two meters (6.6 feet), and providing altitude information to the panoramic and mapping cameras, which were also in the SIM bay.[79]

Light-flash phenomenon and other experiments

Main article: Cosmic ray visual phenomena

Throughout the Apollo lunar missions, the crew members observed light flashes that penetrated closed eyelids. These flashes, described as "streaks" or "specks" of light, were usually observed by astronauts while the spacecraft was darkened during a sleep period. These flashes, while not observed on the lunar surface, would average about two per minute and were observed by the crew members during the trip out to the Moon, back to Earth, and in lunar orbit.[80]

The Apollo 17 crew conducted an experiment, also conducted on Apollo 16, with the objective of linking these light flashes with cosmic rays. As part of an experiment conducted by NASA and the University of Houston, one astronaut wore a device that recorded the time, strength, and path of high-energy atomic particles that penetrated the device. Evidence supports the hypothesis that these flashes occur when charged particles travel through the retina in the eye.[80][81]

Apollo 17 carried a gamma-ray spectrometer in the CM, similar to the ones carried on Apollo 15 and 16. The data from the one on Apollo 17 would be used to help form a baseline, allowing for subtraction of rays from the CM or from cosmic radiation to gain better data from the earlier results.[82] In addition, as on Apollo 14, 15 and 16, the S-band transponders in the CSM and LM were pointed at the Moon to gain data on its gravitational field. Results from the Lunar Orbiter probes had revealed that lunar gravity varies slightly due to the presence of mass concentrations, or "mascons". Data from the missions, and from the lunar subsatellites left by Apollo 15 and 16, were used to map this phenomenon.[83]

Mission events

Launch and outbound trip

Apollo 17 launches on December 7, 1972
Apollo 17 launches on December 7, 1972

Originally planned to launch on December 6, 1972, at 9:53 pm EST (2:53 am on December 7 UTC),[84] Apollo 17 was the final crewed Saturn V launch, and the only one to occur at night. The launch was delayed by two hours and forty minutes due to an automatic cutoff in the launch sequencer at the T-30 second mark in the countdown. The issue was quickly determined to be a minor technical error. The clock was reset and held at the T-22 minute mark while technicians worked around the malfunction in order to continue with the launch. This pause was the only launch delay in the Apollo program caused by this type of hardware failure. The countdown then resumed, and the liftoff occurred at 12:33 am EST on December 7, 1972.[33][85] The launch window, which had begun at the originally-planned launch time of 9:53 pm on December 6, remained open until 1:31 am; there was another window with the same times beginning on the evening of December 7. Had both passed, Apollo 17 would have had to wait until January 4, 1973, to launch.[86]

Approximately 500,000 people were estimated to have observed the launch in the immediate vicinity of Kennedy Space Center, despite the early morning hour. The launch was visible as far away as 800 km (500 mi), and observers in Miami, Florida, reported a "red streak" crossing the northern sky.[85] Among those in attendance at the program's final launch were astronauts Neil Armstrong and Dick Gordon, as well as centenarian Charlie Smith, who alleged he was 130 years old at the time of Apollo 17.[87]

In the hours following the launch, Apollo 17 orbited the Earth while the crew spent time monitoring and checking the spacecraft to ensure its readiness to depart Earth orbit. At 3:46 am EST, the S-IVB third stage was reignited for the 351-second trans-lunar injection burn to propel the spacecraft towards the Moon.[8][33] Despite the launch delay, Apollo 17 would arrive in lunar orbit at the planned time, since ground controllers chose a faster trajectory for it than originally planned.[88] The Command and Service Module separated from the S-IVB approximately half an hour following the S-IVB trans-lunar injection burn, after which Evans turned the spacecraft to face the LM, still attached to the S-IVB. The CSM then docked with the LM and extracted it from the S-IVB. Following the LM extraction, Mission Control programmed the S-IVB, no longer needed to propel the spacecraft, to impact the Moon and trip the seismometers left by prior Apollo crews.[8] It struck the Moon just under 87 hours into the mission, triggering the seismometers from Apollo 12, 14, 15 and 16.[89] Approximately nine hours after launch, the crew concluded the mission's first day with a rest period.[8]

View of Earth from Apollo 17 while in transit to the Moon, a photo now known as The Blue Marble
View of Earth from Apollo 17 while in transit to the Moon, a photo now known as The Blue Marble

Mission Control and the crew decided to shorten the mission's second day, the first full day in space, in order to adjust the crew's wake-up times for the subsequent days in preparation for an early morning (EST) wake-up time on the day of the lunar landing, then scheduled for early afternoon (EST). This was done since the first day of the mission had been extended because of the launch delay. Following the second rest period, and on the third day of the mission, the crew executed the first mid-course correction, a two-second burn of the CSM's service propulsion engine to adjust the spacecraft's Moon-bound trajectory. Following the burn, the crew opened the hatch separating the CSM and LM in order to check the LM's systems and concluded that they were nominal.[8] So that events would take place at the time indicated in the flight plan, the mission clocks were moved ahead by 2 hours and 40 minutes, the amount of the launch delay, with one hour of it at 45:00:00 into the mission and the remainder at 65:00:00.[90]

Among their other activities during the outbound trip, the crew photographed the Earth from the spacecraft as it travelled towards the Moon. One of these photographs is now known as The Blue Marble.[91] The crew also encountered a few issues during the outbound journey; one of the latches holding the CSM and LM together was found to be unlatched. While Schmitt and Cernan were engaged in a second period of LM housekeeping beginning just before sixty hours into the Mission, Evans worked on the balky latch. He was successful, and left it in the position it would need to be in for the CSM-LM docking that would occur upon return from the lunar surface.[92]

Also during the outward journey, the crew performed a heat flow and convection demonstration, as well as the Apollo light-flash experiment. A few hours before entry into lunar orbit, the scientific instrument module door on the SM was jettisoned. At approximately 2:47 pm EST on December 10, the service propulsion system engine on the CSM ignited to slow down the CSM/LM stack into lunar orbit. Following orbit insertion and orbital stabilization, the crew began preparations for the landing at Taurus-Littrow.[33]

Lunar landing

The day of the landing began with a checkout of the Lunar Module's systems, which revealed no issues preventing continuation of the mission. Cernan, Evans, and Schmitt each donned their spacesuits, and Cernan and Schmitt entered the LM in preparation for separating from the CSM and landing. The LM undocked from the CSM, and the two spacecraft orbited close together for about an hour and a half while the astronauts made visual inspections and conducted their final pre-landing checks.[8] After finally separating from the CSM, the LM Challenger and its crew of two adjusted their orbit, such that its lowest point would pass about 10.5 mi (16.9 km) above the landing site, and began preparations for the descent to Taurus-Littrow. While Cernan and Schmitt prepared for landing, Command Module Pilot Ron Evans remained in orbit to take observations, perform experiments and await the return of his crewmates a few days later.[33][8][93]

Soon after completing their preparations for landing and just over two hours following the LM's undocking from the CSM,[1] Cernan and Schmitt began their descent to the Taurus-Littrow valley on the lunar surface with the ignition of the Lunar Module's descent propulsion system (DPS) engine.[1] Approximately ten minutes after the ignition of the DPS engine and the initiation of the powered descent that would land the astronauts on the lunar surface, the LM pitched over, giving Cernan and Schmitt their first look at the landing site during the descent phase and allowing Cernan to guide the spacecraft to a desirable landing target while Schmitt provided data from the flight computer essential for landing. The LM touched down on the lunar surface at 2:55 pm EST on December 11, just over twelve minutes after DPS ignition.[1] Challenger landed about 656 feet (200 m) east of the planned landing point.[94] Shortly thereafter, the two astronauts began re-configuring the LM for their stay on the surface and began preparations for the first moonwalk of the mission, or EVA-1.[33][93]

Lunar surface

Eugene Cernan on the lunar surface, December 13, 1972
Eugene Cernan on the lunar surface, December 13, 1972

During their stay on the lunar surface, Cernan and Schmitt performed three moonwalks (EVAs). The astronauts deployed the LRV, then emplaced the ALSEP and the seismic explosive charges. They drove the rover to nine planned geological survey stations to collect samples and make observations. Additionally, twelve short sampling stops were made at Schmitt's discretion while riding the rover, during which the astronauts used a handled scoop to get a sample, without dismounting.[95] During lunar surface operations, Commander Cernan always drove the rover, while Lunar Module Pilot Schmitt was a passenger who assisted with navigation. This division of responsibilities between the two crew positions was used consistently throughout Apollo's J-missions.[96][97][98]

The first lunar excursion began four hours after landing, at 6:54 p.m. EST on December 11. After exiting through the hatch of the LM and descending the ladder to the footpad, Cernan took the first step on the lunar surface of the mission. Just before doing so, Cernan remarked, "I'm on the footpad. And, Houston, as I step off at the surface at Taurus–Littrow, we'd like to dedicate the first step of Apollo 17 to all those who made it possible."[99] After Cernan surveyed the exterior of the LM and commented on the immediate landing site, Schmitt joined Cernan on the surface.[99] The first task was to offload the rover and other equipment from the LM. While working near the rover, Cernan caught his hammer under the right-rear fender extension, accidentally breaking it off. A similar incident occurred on Apollo 16 as John Young maneuvered around the rover. Although this was not a mission-critical issue, the loss of the part caused Cernan and Schmitt to be covered with dust stirred up when the rover was in motion.[100] The crew made a short-lived fix using duct tape at the beginning of the second EVA, attaching a paper map to the damaged fender. However, lunar dust stuck to the tape's surface, preventing it from adhering properly. Following deployment and testing the maneuverability of the rover, the crew deployed the ALSEP just west of the landing site. The ALSEP deployment took longer than had been planned, with the drilling of core holes presenting some difficulty, meaning the geological portion of the first EVA would need to be shortened, deleting a planned visit to Emory crater. Instead, following the deployment of the ALSEP, Cernan and Schmitt drove to Steno crater, to the south of the landing site. The objective at Steno was to sample the subsurface material excavated by the impact that formed the crater. The astronauts gathered 14 kilograms (31 lb) of samples, took seven gravimeter measurements, and deployed two explosive packages. The latter were later detonated remotely, explosions detected by geophones placed by the astronauts, and also by seismometers left during previous missions.[101] The first EVA ended after seven hours and twelve minutes, with the astronauts back in the LM for a rest period.[33][95][102]

Astronauts Cernan and Schmitt singing "I Was Strolling on the Moon One Day" to the words and tune of the 1884 song "While Strolling Through the Park One Day"
Astronauts Cernan and Schmitt singing "I Was Strolling on the Moon One Day" to the words and tune of the 1884 song "While Strolling Through the Park One Day"

On December 12, awakened by a recording of "Ride of the Valkyries" played from Mission Control,[103] Cernan and Schmitt began their second lunar excursion. The first order of business was to provide the rover's fender a better fix. Overnight, the flight controllers devised a procedure communicated by John Young: taping together four maps, made of a stiff type of paper called "cronopaque",[103] and clamping the "replacement fender extension" onto the fender.[104]: 977  The astronauts carried out the new fix which did its job, lasting the remainder of the exploration.[100][105][106] Cernan and Schmitt then departed for station 2—Nansen Crater, at the foot of the South Massif. When they arrived, their range from the Challenger was 7.6 kilometers[104]: 1144  (4.7 miles, 25,029 feet[5]). This remains the furthest distance any spacefarers have ever traveled away from the safety of a pressurizable spacecraft while on a planetary body,[107] and also during an EVA of any type.[a] The astronauts were at the extremity of their "walkback limit", a safety constraint meant to ensure that they could walk back to the LM if the rover failed. They began a return trip, traveling northeast in the rover. Stopping at station 4—Shorty crater—the astronauts discovered orange soil, which proved to be very small beads of volcanic glass formed over 3.5 billion years ago.[109] This discovery caused great excitement among the scientists at Mission Control, who felt that the astronauts may have discovered a volcanic vent. This did not prove to be the case; Shorty is an impact crater, but the orange soil is the remnant of a fire fountain, molten lava sprayed high into the lunar sky from lava which had upwelled there in the Moon's early days, some 3.5 billion years ago, and was then covered by lava until exposed by the impact that formed Shorty, less than 20 million years ago.[110]

The final stop before returning to the LM was Camelot crater; throughout the sojourn, the astronauts collected 34 kilograms (75 lb) of samples, took another seven gravimeter measurements, and deployed three more explosive packages.[33] Concluding the EVA at seven hours and thirty-seven minutes, Cernan and Schmitt had completed the longest-duration EVA in history to-date, traveling further away from a spacecraft and covering more ground on a planetary body during a single EVA than any other spacefarers.[5] Once the LM was repressurized, CAPCOM Bob Parker was particularly impressed, saying: "Absolutely outstanding. I can't say more than that. And I mean it from the bottom of my heart or the bottom of my soul or something, my conscience."[104]: 1363 

Composite image of Harrison Schmitt working next to Tracy's Rock during EVA-3
Composite image of Harrison Schmitt working next to Tracy's Rock during EVA-3

The third moonwalk, the last of the Apollo program, began at 5:25 pm EST on December 13. Cernan and Schmitt rode the rover northeast of the landing site, exploring the base of the North Massif and the Sculptured Hills. Stopping at station 6, they examined a house-sized split boulder dubbed Tracy's Rock (or Split Rock), after Cernan's daughter. The ninth and final planned station was conducted at Van Serg crater. The crew collected 66 kilograms (146 lb) of lunar samples and took another nine gravimeter measurements.[33] Schmitt had seen a fine-grained rock, unusual for that vicinity, earlier in the mission and had stood it on its edge; before closing out the EVA, he went and got it. Subsequently, designated Sample 70215, it was, at 17.7 pounds (8.0 kg), the largest rock brought back by Apollo 17. A small piece of it is on exhibit at the Smithsonian Institution, one of the few rocks from the Moon that the public may touch.[111] Schmitt also collected a sample, designated as Sample 76535, at geology station 6 near the base of the North Massif; the sample, a troctolite, was later identified as the oldest known "unshocked" lunar rock, meaning it has not been damaged by high-impact geological events. Scientists have therefore used Sample 76535 in thermochronological studies to determine if the Moon formed a metallic core or, as study results suggest, a core dynamo.[112][113]

Before concluding the moonwalk, the crew collected a breccia rock, dedicating it to the nations of Earth, 70 of which were represented by students touring the U.S. and present in Mission Control Center in Houston, Texas, at the time. Portions of this sample, known as the Friendship Rock, were subsequently distributed to the nations represented by the students. A plaque located on the LM, commemorating the achievements made during the Apollo program, was then unveiled. Before reentering the LM for the final time, Gene Cernan remarked,[33][114]

... I'm on the surface; and, as I take man's last step from the surface, back home for some time to come – but we believe not too long into the future – I'd like to just [say] what I believe history will record. That America's challenge of today has forged man's destiny of tomorrow. And, as we leave the Moon at Taurus-Littrow, we leave as we came and, God willing, as we shall return, with peace and hope for all mankind. "Godspeed the crew of Apollo 17."[115]

Cernan then followed Schmitt into the LM; the final lunar excursion had a duration of seven hours and fifteen minutes.[33] Following closing of the LM hatch and repressurization of the LM cabin, Cernan and Schmitt removed their spacesuits and reconfigured the cabin for a final rest period on the lunar surface. As they did following each of the previous two EVAs, Cernan and Schmitt discussed their geological observations from the day's excursion with mission control while preparing to rest.[116]

Solo activities

While Cernan and Schmitt were on the lunar surface, Ron Evans remained alone in the CSM in lunar orbit, having been assigned a number of observational and scientific tasks while awaiting the return of his crewmates. In addition to the operation of the various orbital science equipment contained in the CSM's SIM bay, Evans conducted both visual and photographic observation of surface features from his aerial vantage point.[117] The orbit of the CSM having been modified to an elliptical orbit in preparation for the LM's departure and eventual descent, one of Evans' first solo tasks in the CSM was to circularize its orbit such that the CSM would remain at approximately the same distance above the surface throughout its orbit. Thereafter, Evans began his observation of ten visual targets that had been assigned prior to launch, all of which were successfully identified during the course of the mission. Photographically, Evans focused on surface features as well as the solar corona at "sunrise," or the period of time during which the CSM would pass from the darkened portion of the Moon to the illuminated portion when the Moon itself mostly obscured the sun. To photograph portions of the surface that were not illuminated by the sun while Evans passed over them, Evans relied in conjunction on exposure and Earthlight. Evans photographed such features as the craters Eratosthenes and Copernicus, as well as the vicinity of Mare Orientale, using this technique.[118] According to the Apollo 17 Mission Report, Evans was able to capture all scientific photographic targets, as well as some other targets of interest.[119]

An oblique, black-and-white view of a portion of Mare Orientale from the CSM, illustrating the illuminating effect of Earthlight on the lunar terrain below during local nighttime; Evans reported seeing a light "flash" apparently originating from the surface in this area
An oblique, black-and-white view of a portion of Mare Orientale from the CSM, illustrating the illuminating effect of Earthlight on the lunar terrain below during local nighttime; Evans reported seeing a light "flash" apparently originating from the surface in this area

Similarly to the crew of Apollo 16, Evans (as well as Schmitt, while in lunar orbit) reported seeing light "flashes" apparently originating from the lunar surface, known as transient lunar phenomena (TLP); Evans reported seeing these "flashes" in the vicinity of Grimaldi crater and Mare Orientale. The causes of TLP are not well-understood and, though inconclusive as an explanation, both of the sites in which Evans reported seeing TLP are the general locations of outgassing from the Moon's interior. Meteorite impacts are another possible explanation.[120][121]

The flight plan kept Evans busy almost constantly, making him so tired he overslept one morning by an hour, despite the efforts of Mission Control to awaken him. Before the LM departed for the lunar surface, Evans had discovered that he had misplaced his pair of scissors, necessary to open food packets. Cernan and Schmitt lent him one of theirs.[122] The instruments in the SIM bay functioned without significant hindrance during the orbital portion of the mission, though the two antennas of the lunar sounder as well as the mapping camera encountered minor issues. The indicator on the instrument panel for the extension of one of the sounder's antennas was not functional and the second antenna suffered an apparent stall during its extension. Despite these technical difficulties, both antennas were deployed fully and the sounder achieved its planned observational purpose. Similarly, the extension and retraction of the mapping camera took longer than planned (about four minutes, longer than the nominal two) and, though deployment and retraction was not otherwise hindered, the use of this piece of equipment was reduced to avoid exhausting it by overuse.[123]

Evans was also responsible for piloting the CSM during the orbital phase of the mission, maneuvering the spacecraft to alter and maintain its orbital trajectory. In addition to the initial orbital recircularization maneuver shortly after the LM's departure, one of the final significant solo activities Evans performed in the CSM in preparation for the return of his crewmates from the lunar surface was the plane change maneuver. This maneuver was meant to align the CSM's trajectory to the eventual trajectory of the LM to facilitate rendezvous in orbit. Evans fired the SPS engine of the CSM for about 20 seconds in successfully adjusting the CSM's orbital plane.[123]

Return to Earth

Apollo 17 post-splashdown recovery operations
Apollo 17 post-splashdown recovery operations

Following a rest period after the third and final moonwalk and preparations to return to lunar orbit, Eugene Cernan and Harrison Schmitt successfully lifted off from the lunar surface in the ascent stage of the LM on December 14, at 5:54 pm EST. The return to lunar orbit took just over seven minutes.[1] The LM and its crew successfully rendezvoused and docked with the CSM, in which Ron Evans had remained, about two hours after liftoff from the surface. Thereafter, the crew transferred equipment and lunar samples between the LM and the CSM for return to Earth. The crew sealed the hatches between the CSM and the LM ascent stage following completion of the transfer and the LM was jettisoned at 11:51 pm EST on December 14.[1] The unoccupied ascent stage was then remotely crashed into the Moon on purpose in a collision recorded by seismometers deployed on Apollo 17 and previous Apollo expeditions.[33][124] At 6:35 pm EST on December 16, the CSM's SPS engine was ignited once more to propel the spacecraft away from the Moon on a trajectory back towards Earth. The successful trans-Earth injection SPS burn lasted just over two minutes.[1]

During the return to Earth, Evans performed a 65-minute EVA to retrieve film cassettes from the service module's scientific instrument module (SIM) bay, with assistance from Schmitt who remained at the command module's hatch. At approximately 160,000 nautical miles[125]: 1730  (184,000 mi; 296,000 km) from Earth, it was the third "deep space" EVA in history, performed at great distance from any planetary body. As of 2022, it remains one of only three such EVAs, all performed during Apollo's J-missions under similar circumstances. It was the last EVA of the Apollo program.[33][126]

During the trip back to Earth, the crew operated the infrared radiometer in the SM, as well as the ultraviolet spectrometer. One midcourse correction was performed, lasting 9 seconds.[127] On December 19, the crew jettisoned the no-longer-needed SM, leaving only the CM for return to Earth. The Apollo 17 spacecraft reentered Earth's atmosphere and splashed down safely in the Pacific Ocean at 2:25 pm EST, 6.4 kilometers (4.0 mi) from the recovery ship, USS Ticonderoga. Cernan, Evans, and Schmitt were then retrieved by a recovery helicopter and were safely aboard the recovery ship 52 minutes after splashdown.[33][124] As the final Apollo mission concluded successfully, Mission Control in Houston was filled with many former flight controllers and astronauts, who applauded as America returned to Earth.[128]

Aftermath and spacecraft locations

None of the Apollo 17 astronauts flew in space again.[129] Cernan retired from NASA and the Navy in 1976. He died in 2017.[130] Evans retired from the Navy in 1976 and from NASA in 1977, entering the private sector. He died in 1990.[131] Schmitt resigned from NASA in 1975 prior to his successful run for a United States Senate seat from New Mexico in 1976. There, he served one six-year term.[4]

Apollo 17 command module America, on display at Space Center Houston
Apollo 17 command module America, on display at Space Center Houston

The Command Module America is currently on display at Space Center Houston at the Lyndon B. Johnson Space Center in Houston, Texas.[132][133] The ascent stage of Lunar Module Challenger impacted the Moon on December 15, 1972, at 06:50:20.8 UTC (1:50 am EST), at 19°58′N 30°30′E / 19.96°N 30.50°E / 19.96; 30.50 (Apollo 17 LM ascent stage).[132] The descent stage remains on the Moon at the landing site, 20°11′27″N 30°46′18″E / 20.19080°N 30.77168°E / 20.19080; 30.77168 (Apollo 17 LM descent stage).[6] Eugene Cernan's flown Apollo 17 spacesuit is on display at the Smithsonian's National Air and Space Museum (NASM), where it was transferred in 1974,[134] and Harrison Schmitt's is in storage at NASM's Paul E. Garber Facility. Amanda Young of NASM indicated in 2004 that Schmitt's suit is in the best condition of the flown Apollo lunar spacesuits, and therefore is not on public display.[135]

Since Apollo 17's return, there have been attempts to photograph and plans to visit the landing site, where some of the mission hardware, such as the LM's descent stage and the LRV, remains. In 2009 and again in 2011, the Lunar Reconnaissance Orbiter photographed the landing site from increasingly low orbits[136] and, in 2018, the German space company PTScientists indicated that it was planning to land two lunar rovers near the landing site.[137]

See also

Note

  1. ^ Apart from the Apollo program's moonwalks (and a unique trio of deep-space EVAs conducted during the program's J-missions), all other spacewalks have been conducted in Low-Earth orbit, of which almost all have involved a safety tether keeping the spacefarer attached to the spacecraft by a short distance. The exceptions occurred in 1984 and 1994, when a series of seven EVAs involved untethered activity using the Manned Maneuvering Unit (MMU) and the Simplified Aid For EVA Rescue Unit (SAFER). Among this latter group, the greatest distance traveled away from a spacecraft during orbital flight was approximately 100 meters (320 feet), achieved by Bruce McCandless on STS-41-B during the first test of the MMU.[108]

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