Editing Apollo 17 (section)

== Mission events ==

=== Launch and outbound trip ===
[[File:Apollo 17 liftoff.jpg|thumb|right|Apollo 17 launches on December 7, 1972]]

Originally planned to launch on December 6, 1972, at 9:53&nbsp;p.m. [[Eastern Standard Time (North America)|EST]] (2:53&nbsp;a.m. on December 7 UTC),{{sfn|Orloff & Harland 2006|p=510}} Apollo 17 was the final crewed Saturn{{nbsp}}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 cause of the problem was quickly determined to be the launch sequencer's failure to automatically pressurize the liquid oxygen tank in the third stage of the rocket; although launch control noticed this and manually caused the tank to pressurize, the sequencer did not recognize the fix and therefore paused the countdown. 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 a hardware problem. The countdown then resumed, and the liftoff occurred at 12:33&nbsp;a.m. EST on December 7, 1972.<ref name=astronautix/><ref name=launchops>{{cite web|title=Apollo 17 Launch Operations|url=http://www.hq.nasa.gov/office/pao/History/SP-4204/ch23-7.html|publisher=NASA|access-date=November 16, 2011|archive-date=October 27, 2011|archive-url=https://web.archive.org/web/20111027162938/http://www.hq.nasa.gov/office/pao/History/SP-4204/ch23-7.html|url-status=live}}</ref> The launch window, which had begun at the originally planned launch time of 9:53&nbsp;p.m. on December 6, remained open until 1:31&nbsp;a.m., the latest time at which a launch could have occurred during the December 6–7 window.{{sfn|Orloff 2004|loc=Statistical Tables: Launch Windows}}

Approximately 500,000 people observed the launch in the immediate vicinity of Kennedy Space Center, despite the early-morning hour. The launch was visible as far away as {{convert|800|km|mi nmi|abbr=on}}, and observers in [[Miami|Miami, Florida]], reported a "red streak" crossing the northern sky.<ref name=launchops/> Among those in attendance at the program's final launch were astronauts [[Neil Armstrong]] and Dick Gordon, as well as centenarian [[Charlie Smith (centenarian)|Charlie Smith]], who alleged he was 130 years old at the time of Apollo 17.{{sfn|Chaikin 1995|pp=495, 498}}

The ascent resulted in an orbit with an altitude and velocity almost exactly that which had been planned.{{sfn|Orloff & Harland 2006|p=511}} 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&nbsp;a.m. EST, the S-IVB third stage was reignited for the 351-second [[trans-lunar injection]] burn to propel the spacecraft towards the Moon.<ref name="a17pre"/><ref name=astronautix>{{cite web|last=Wade|first=Mark|title=Apollo 17|url=http://www.astronautix.com/flights/apollo17.htm|publisher=Encyclopedia Astronautica|access-date=August 22, 2011|url-status=dead|archive-url=https://web.archive.org/web/20110812193502/http://www.astronautix.com/flights/apollo17.htm|archive-date=August 12, 2011}}</ref> Ground controllers chose a faster trajectory for Apollo 17 than originally planned to allow the vehicle to reach lunar orbit at the planned time, despite the launch delay.{{sfn|Orloff & Harland 2006|p=514}} 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.<ref name="a17pre"/> It struck the Moon just under 87 hours into the mission, triggering the seismometers from Apollo 12, 14, 15 and 16.{{sfn|Orloff & Harland 2006|p=214}} Approximately nine hours after launch, the crew concluded the mission's first day with a sleep period, until waking up to begin the second day.<ref name="a17pre"/>

[[File:The Earth seen from Apollo 17.jpg|thumb|upright=1.2|left|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.<ref name="a17pre"/> 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.<ref name="jump">{{cite web|title=Day 4, part 1: Clock update|date=December 26, 2017|access-date=November 24, 2021|editor-first=David|editor-last=Woods|editor2-first=Ben|editor2-last=Feist|publisher=NASA|url=https://history.nasa.gov/afj/ap17fj/09_day04_part1_clock_update.html|work=Apollo 17 Flight Journal|archive-date=July 21, 2019|archive-url=https://web.archive.org/web/20190721143515/https://history.nasa.gov/afj/ap17fj/09_day04_part1_clock_update.html|url-status=live}}</ref>

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]]''.<ref>{{cite magazine |url=https://time.com/3879555/blue-marble-apollo-17-photo-of-earth-from-space/ |title=Home, Sweet Home: In Praise of Apollo 17's 'Blue Marble' |last=Cosgrove |first=Ben |magazine=[[Time (magazine)|Time]] |date=April 11, 2014 |access-date=December 7, 2019 |url-status=dead |archive-url=https://web.archive.org/web/20150601092710/https://time.com/3879555/blue-marble-apollo-17-photo-of-earth-from-space/ |archive-date=June 1, 2015}}</ref> The crew found that one of the latches holding the CSM and LM together was 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.{{sfn|Orloff & Harland 2006|pp=514–515}}

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 SIM door on the SM was jettisoned. At approximately 2:47&nbsp;p.m. 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.<ref name=astronautix/>

=== Lunar landing ===
[[File:AS17-147-22465 (21678759595).jpg|thumb|upright=1.4|The valley of [[Taurus-Littrow]] as seen from the [[Apollo Lunar Module|Lunar Module]] ''Challenger'' on the orbit before powered descent there. The [[Apollo command and service module|Command and Service Module]] ''America'' can just be seen crossing the base of the 2.3 km high South Massif. Between the South and North Massifs, the valley is 7 km wide. [[Mare Serenitatis]], the Sea of Serenity, is on the horizon.]]
The day of the landing began with a checkout of the Lunar Module's systems, which revealed no problems 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.<ref name="a17pre"/> 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 {{convert|10.5|mi|km|abbr=on}} above the landing site, and began preparations for the descent to Taurus–Littrow. While Cernan and Schmitt prepared for landing, Evans remained in orbit to take observations, perform experiments and await the return of his crewmates a few days later.<ref name=astronautix/><ref name="a17pre"/><ref name=alsjland>{{cite web|title=Landing at Taurus-Littrow|url=http://www.hq.nasa.gov/alsj/a17/a17.landing.html|publisher=NASA|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 17 Lunar Surface Journal|access-date=August 22, 2011|archive-date=September 7, 2011|archive-url=https://web.archive.org/web/20110907123428/http://www.hq.nasa.gov/alsj/a17/a17.landing.html|url-status=live}}</ref>

Soon after completing their preparations for landing and just over two hours following the LM's undocking from the CSM, 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.<ref name=alsjland/>{{sfn|Orloff & Harland 2006|p=519}} Approximately ten minutes later, as planned, 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&nbsp;p.m. EST on December 11, just over twelve minutes after DPS ignition.{{sfn|Orloff & Harland 2006|p=519}} ''Challenger'' landed about {{convert|656|ft}} east of the planned landing point.{{sfn|Orloff & Harland 2006|p=515}} 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.<ref name=astronautix/><ref name=alsjland/>

=== Lunar surface ===

====First EVA====
[[File:Apollo 17 Cernan on moon.jpg|thumb|upright=1.3|right|Cernan on the lunar surface, December 13, 1972]]

During their approximately 75-hour stay{{sfn|Orloff 2004|loc=Statistical Tables: General Background}} on the lunar surface, Cernan and Schmitt performed three moonwalks ([[Extra-vehicular activity|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.<ref name="geostations">{{cite web |url=https://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/surface_opp/ |title=Apollo 17 Mission: Surface Operations Overview |publisher=Lunar and Planetary Institute |website=Universities Space Research Association |access-date=November 29, 2021 |archive-date=November 9, 2020 |archive-url=https://web.archive.org/web/20201109201434/https://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/surface_opp/ |url-status=live }}</ref> 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.<ref name="cdrdriver">{{cite web|url=https://www.hq.nasa.gov/alsj/a15/a15.summary.html|title=Apollo 15 Mission Summary: Mountains of the Moon|publisher=NASA|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 15 Lunar Surface Journal|access-date=January 6, 2022|archive-date=July 21, 2019|archive-url=https://web.archive.org/web/20190721143222/https://www.hq.nasa.gov/alsj/a15/a15.summary.html|url-status=live}}</ref>{{sfn|Riley, Woods, & Dolling 2012|p=165}}<ref name="reunion">{{cite web |url=https://www.space.com/apollo-astronauts-talk-risks-explorers-club-2019.html |title=The Risk of Apollo: Astronauts Swap Harrowing Tales from NASA's Moon Shots |last=Gohd |first=Chelsea |date=March 22, 2019 |website=[[Space.com]] |access-date=January 6, 2022 |archive-date=July 26, 2020 |archive-url=https://web.archive.org/web/20200726063901/https://www.space.com/apollo-astronauts-talk-risks-explorers-club-2019.html |url-status=live }}</ref>

The first lunar excursion began four hours after landing, at 6:54&nbsp;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."<ref name="firststeps">{{cite web|title=Down the Ladder|url=https://www.hq.nasa.gov/alsj/a17/a17.1ststep.html|publisher=NASA|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 17 Lunar Surface Journal|access-date=January 6, 2022|archive-date=July 21, 2019|archive-url=https://web.archive.org/web/20190721181802/https://www.hq.nasa.gov/alsj/a17/a17.1ststep.html|url-status=live}}</ref> After Cernan surveyed the exterior of the LM and commented on the immediate landing site, Schmitt joined Cernan on the surface.<ref name="firststeps"/> 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.<ref name="brokenfender">{{cite web|title=ALSEP Off-load|url=http://www.hq.nasa.gov/alsj/a17/a17.alsepoff.html|publisher=NASA|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 17 Lunar Surface Journal|access-date=August 24, 2011|archive-date=August 16, 2015|archive-url=https://web.archive.org/web/20150816205258/http://www.hq.nasa.gov/alsj/a17/a17.alsepoff.html|url-status=live}}</ref> 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. Lunar dust stuck to the tape's surface, however, 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, cancelling a planned visit to [[Emory (crater)|Emory crater]]. Instead, following the deployment of the ALSEP, Cernan and Schmitt drove to [[Steno-Apollo|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 {{convert|14|kg|lbs}} of samples, took seven gravimeter measurements, and deployed two explosive packages. The explosive packages were later detonated remotely; the resulting explosions detected by geophones placed by the astronauts and also by seismometers left during previous missions.<ref>{{cite journal |last1=Brzostowski |first1=Matthew |last2=Brzostowski |first2=Adam |date=April 2009 |title=Archiving the Apollo active seismic data |url=http://tle.geoscienceworld.org/content/28/4/414.abstract |journal=[[Society of Exploration Geophysicists#Journals, books, and newsletters|The Leading Edge]] |location=Tulsa, OK |publisher=[[Society of Exploration Geophysicists]] |volume=28 |issue=4 |pages=414–416 |doi=10.1190/1.3112756 |bibcode=2009LeaEd..28..414B |issn=1070-485X |access-date=June 12, 2014 |archive-date=November 4, 2016 |archive-url=https://web.archive.org/web/20161104200304/http://tle.geoscienceworld.org/content/28/4/414.abstract |url-status=live }}</ref> The first EVA ended after seven hours and twelve minutes.<ref name=astronautix/> and the astronauts remained in the pressurized LM for the next 17 hours.{{sfn|Orloff & Harland 2006|p=516}}

====Second EVA====
[[File:Ap17 strolling.ogv|thumb|Astronauts Cernan and Schmitt singing "I Was Strolling on the Moon One Day" to the words and tune of the 1884 song "[[The Fountain in the Park|While Strolling Through the Park One Day]]"]]
On December 12, awakened by a recording of "[[Ride of the Valkyries]]" played from Mission Control,<ref name="valkyries">{{cite web|url=https://www.hq.nasa.gov/alsj/a17/a17.eva2wake.html|title=EVA-2 Wake-up|publisher=NASA|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 17 Lunar Surface Journal|date=May 20, 2014|access-date=January 7, 2022|archive-date=July 21, 2019|archive-url=https://web.archive.org/web/20190721171500/https://www.hq.nasa.gov/alsj/a17/a17.eva2wake.html|url-status=live}}</ref> 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 controller]]s devised a procedure communicated by John Young: taping together four stiff paper maps<ref name="valkyries"/> to form a "replacement fender extension" and then clamping it onto the fender.<ref name="transcript">{{cite web |url=https://www.hq.nasa.gov/alsj/a17/AS17_TEC.PDF |archive-url=https://ghostarchive.org/archive/20221009/https://www.hq.nasa.gov/alsj/a17/AS17_TEC.PDF |archive-date=2022-10-09 |url-status=live |title=Apollo 17 Technical Air-to-Ground Voice Transcription |publisher=NASA |date=December 1972|page=977}}</ref> The astronauts carried out the new fix which did its job without failing until near the end of the third excursion.{{sfn|Chaikin 1995|p=542}}{{sfn|Swift 2021|pp=1043–1045, 1085}} Cernan and Schmitt then departed for station 2—[[Nansen-Apollo (crater)|Nansen Crater]], at the foot of the South Massif. When they arrived, their range from the ''Challenger'' was 7.6 kilometers (4.7 miles, 25,029 feet<ref name="eva table">{{cite web |url=https://history.nasa.gov/SP-4029/Apollo_18-30_Extravehicular_Activity.htm |title=Extravehicular Activity |publisher=NASA |access-date=January 6, 2022 |archive-date=November 18, 2004 |archive-url=https://web.archive.org/web/20041118103553/https://history.nasa.gov/SP-4029/Apollo_18-30_Extravehicular_Activity.htm |url-status=live }}</ref>). This remains the furthest distance any spacefarers have ever traveled away from the safety of a pressurizable spacecraft while on a planetary body,{{sfn|Swift 2021|pp=1053–1058}} and also during an EVA of any type.{{efn|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 II|Bruce McCandless]] on [[STS-41-B]] during the first test of the MMU.<ref>{{cite web |last=Chaikin |first=Andrew |title=Untethered |date=October 2014 |publisher=Air and Space Magazine |url=https://www.airspacemag.com/space/untethered-180952792/ |access-date=January 6, 2022 |archive-date=December 14, 2021 |archive-url=https://web.archive.org/web/20211214000747/https://www.airspacemag.com/space/untethered-180952792/ |url-status=live }}</ref>}} 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.{{sfn|Chaikin 1995|pp=527–530}}

At station 3, Schmitt fell to the ground while working, looking so awkward that Parker jokingly told him that NASA's switchboard had lit up seeking Schmitt's services for Houston's ballet group, and the site of station 3 was in 2019 renamed Ballet Crater.{{sfn|Swift 2021|pp=1062–1063}} Cernan took a sample at Station 3 that was to be maintained in vacuum until better analytical techniques became available, joking with the CAPCOM, Parker, about placing a note inside. The container remained unopened until 2022.<ref name="transcript"/><ref>{{cite web|last=Wamsley|first=Laurel|title=NASA is just now opening a vacuum-sealed sample it took from the moon 50 years ago|publisher=[[National Public Radio]]|access-date=March 11, 2022|url=https://www.npr.org/2022/03/08/1085241811/nasa-moon-samples-apollo-artemis|date=March 8, 2022|archive-date=March 11, 2022|archive-url=https://web.archive.org/web/20220311021647/https://www.npr.org/2022/03/08/1085241811/nasa-moon-samples-apollo-artemis|url-status=live}}</ref>

Stopping at station 4—[[Shorty (crater)|Shorty crater]]—the astronauts discovered orange soil, which proved to be very small beads of volcanic glass formed over 3.5 billion years ago.{{sfn|Cortright 2019|p=276}} This discovery caused great excitement among the scientists at Mission Control, who felt that the astronauts may have discovered a volcanic vent. However, post-mission sample analysis revealed that Shorty is not a volcanic vent, but rather an impact crater. Analysis also found the orange soil to be a remnant of a [[lava fountain]]. This lava fountain sprayed molten lava high into the lunar sky in the Moon's early days, some 3.5 billion years ago and long before Shorty's creation. The orange volcanic beads were droplets of molten lava from the fountain that solidified and were buried by lava deposits until exposed by the impact that formed Shorty, less than 20 million years ago.{{sfn|Chaikin 1995|pp=527–530}}

The final stop before returning to the LM was [[Camelot (crater)|Camelot crater]]; throughout the sojourn, the astronauts collected {{convert|34|kg|lbs}} of samples, took another seven gravimeter measurements, and deployed three more explosive packages.<ref name=astronautix/> 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.<ref name="eva table"/> The improvised fender had remained intact throughout, causing the president of the "Auto Body Association of America" to award them honorary lifetime membership.{{sfn|Swift 2021|pp=1070–1071}}

====Third EVA==== 
[[File:AS17-140-21493+AS17-140-21497.jpg|thumb|upright=1.5|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&nbsp;p.m. 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)|Van Serg crater]]. The crew collected {{convert|66|kg|lbs}} of lunar samples and took another nine gravimeter measurements.<ref name=astronautix/> 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 {{convert|17.7|lb}}, 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.<ref>{{cite journal|last=Craddock|first=Bob|title=In the Museum: The Rock|date=March 2002|journal=[[Air & Space/Smithsonian]]|url=https://www.airspacemag.com/space/in-the-museum-the-rock-28431174/|access-date=December 4, 2021|archive-date=December 4, 2021|archive-url=https://web.archive.org/web/20211204210836/https://www.airspacemag.com/space/in-the-museum-the-rock-28431174/|url-status=live}}</ref> Schmitt also collected a sample, designated as [[Troctolite 76535|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 [[Thermochronology|thermochronological]] studies to determine if the Moon formed a metallic [[Planetary core|core]] or, as study results suggest, a [[Dynamo theory|core dynamo]].<ref>{{cite journal|last=Garrick-Bethell|first=Ian|display-authors=etal |title=Early Lunar Magnetism|journal=Science|date=January 2009|volume=323|pages=356–359|doi=10.1126/science.1166804|pmid=19150839|bibcode=2009Sci...323..356G|issue=5912|s2cid=23227936}}</ref><ref>{{cite web |title=Lunar Sample 76535 |url=https://www.lpi.usra.edu/lunar/samples/atlas/detail/?mission=Apollo%2017&sample=76535 |publisher=Lunar and Planetary Institute |access-date=December 13, 2021 |archive-date=June 25, 2021 |archive-url=https://web.archive.org/web/20210625061132/https://www.lpi.usra.edu/lunar/samples/atlas/detail/?mission=Apollo%2017&sample=76535 |url-status=live }}</ref>

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 [[Christopher C. Kraft Jr. Mission Control Center#Houston (1965–present)|Mission Control Center]] in [[Houston|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, Cernan remarked,<ref name=astronautix/>{{sfn|Chaikin 1995|p=543}}

{{blockquote|text= ...{{nbsp}}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."<ref name=alsjeva3>{{cite web|title=EVA-3 Close-out|url=http://www.hq.nasa.gov/alsj/a17/a17.clsout3.html|publisher=NASA|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 17 Lunar Surface Journal|access-date=August 22, 2011| archive-url= https://web.archive.org/web/20110718153102/http://www.hq.nasa.gov/alsj/a17/a17.clsout3.html| archive-date=July 18, 2011| url-status= live}}</ref>}}

Cernan then followed Schmitt into the LM; the final lunar excursion had a duration of seven hours and fifteen minutes.<ref name=astronautix/> 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.<ref>{{cite web|title=Post-EVA-3 Activities|url=https://www.hq.nasa.gov/alsj/a17/a17.eva3post.html|publisher=NASA|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 17 Lunar Surface Journal|access-date=December 11, 2021|archive-date=December 13, 2021|archive-url=https://web.archive.org/web/20211213180515/https://www.hq.nasa.gov/alsj/a17/a17.eva3post.html|url-status=live}}</ref>

=== Solo activities ===
While Cernan and Schmitt were on the lunar surface, Evans remained alone in the CSM in lunar orbit and was assigned a number of observational and scientific tasks to perform 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.<ref name="evans">{{cite web |title=Ronald E. Evans |url=https://www.nmspacemuseum.org/inductee/ronald-e-evans/ |publisher=New Mexico Museum of Space History |access-date=February 8, 2022 |archive-date=January 26, 2022 |archive-url=https://web.archive.org/web/20220126011723/https://www.nmspacemuseum.org/inductee/ronald-e-evans/ |url-status=live }}</ref> 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' 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.<ref>{{cite web |last1=Fowler |first1=Wallace T. |title=Apollo Timeline (Apollo 17) |url=http://www.tsgc.utexas.edu/spacecraft/apollo17/timeline.html |website=Lunar Mission Characteristics |publisher=University of Texas |access-date=February 8, 2022 |archive-date=February 8, 2022 |archive-url=https://web.archive.org/web/20220208230120/http://www.tsgc.utexas.edu/spacecraft/apollo17/timeline.html |url-status=dead }}</ref> Evans observed geological features visible to him and used handheld cameras to record certain visual targets.<ref name="evans"/> Evans also observed and sketched 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.<ref>{{cite journal |last1=Zook |first1=H. A. |last2=Potter |first2=A. E. |last3=Cooper |first3=B. L. |title=The Lunar Dust Exosphere and Clementine Lunar Horizon Glow |journal=Abstracts of the Lunar and Planetary Science Conference |date=1995 |volume=26 |page=1577 |bibcode=1995LPI....26.1577Z |url=https://adsabs.harvard.edu/full/1995LPI....26.1577Z |access-date=February 8, 2022 |archive-date=February 8, 2022 |archive-url=https://web.archive.org/web/20220208231558/https://adsabs.harvard.edu/full/1995LPI....26.1577Z |url-status=live }}</ref> To photograph portions of the surface that were not illuminated by the sun while Evans passed over them, Evans relied in conjunction on [[Exposure (photography)|exposure]] and [[Earthlight (astronomy)|Earthlight]]. Evans photographed such features as the craters [[Eratosthenes (crater)|Eratosthenes]] and Copernicus, as well as the vicinity of [[Mare Orientale]], using this technique.{{sfn|Apollo 17 Mission Report|pp=10-34–10-38}} According to the Apollo 17 Mission Report, Evans was able to capture all scientific photographic targets, as well as some other targets of interest.{{sfn|Apollo 17 Mission Report|p=10-37}}

[[File:AS17-158-23902.jpg|thumb|left|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 phenomenon|transient lunar phenomena]] (TLP); Evans reported seeing these "flashes" in the vicinity of [[Grimaldi (crater)|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 rock|outgassing]] from the Moon's interior. [[Meteorite]] impacts are another possible explanation.{{sfn|Crotts 2014|pp=268–269}}<ref>{{cite web |title=Transient Lunar Phenomena Studies |url=http://user.astro.columbia.edu/~arlin/TLP/ |publisher=Columbia University |access-date=December 12, 2021 |archive-date=January 27, 2022 |archive-url=https://web.archive.org/web/20220127044000/http://user.astro.columbia.edu/~arlin/TLP/ |url-status=live }}</ref>

The flight plan kept Evans busy, 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.{{sfn|Chaikin 1995|p=532}} The instruments in the SIM bay functioned without significant hindrance during the orbital portion of the mission, though the lunar sounder and the mapping camera encountered minor problems.{{sfn|Apollo 17 Mission Report|p=10-38}} Evans spent approximately 148 total hours in lunar orbit, including solo time and time spent together with Cernan and Schmitt, which is more time than any other individual has spent orbiting the Moon.{{sfn|Orloff 2004|loc=Statistical Tables: General Background}}<ref>{{cite news |last1=Howell |first1=Elizabeth |title=Ron Evans: Apollo 17 Command Module Pilot |url=https://www.space.com/20788-ron-evans-astronaut-biography.html |access-date=February 12, 2022 |publisher=Space.com |date=April 23, 2013 |archive-date=December 1, 2017 |archive-url=https://web.archive.org/web/20171201033841/https://www.space.com/20788-ron-evans-astronaut-biography.html |url-status=live }}</ref>

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 solo activities Evans performed in the CSM in preparation for the return of his crewmates from the lunar surface was the [[Orbital plane (astronomy)|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.{{sfn|Orloff 2004|loc=Apollo 17: The Eleventh Mission}}{{sfn|Apollo 17 Mission Report|p=10-38}}

=== Return to Earth ===
[[File:SH-3 Sea King of HC-1 recovers Apollo 17 astronauts off USS Ticonderoga (CVS-14), 19 December 1972 (Ap17-S72-55974).jpg|thumb|right|Apollo 17 post-splashdown recovery operations]]

Cernan and Schmitt lifted off from the lunar surface in the ascent stage of the LM on December{{nbsp}}14, at 5:54&nbsp;p.m. EST. The return to lunar orbit took just over seven minutes.{{sfn|Orloff & Harland 2006|p=518}} The LM, piloted by Cernan, and the CSM, piloted by Evans, maneuvered, and redocked about two hours after liftoff from the surface. After docking, the crew transferred equipment and lunar samples from the LM to the CSM for return to Earth.{{sfn|Orloff & Harland 2006|p=519}}<ref name=alsjreturn/> 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&nbsp;p.m. EST on December{{nbsp}}14. The unoccupied ascent stage was then remotely deorbited, crashing it into the Moon with an impact recorded by the seismometers left by Apollo 17 and previous missions.<ref name=astronautix/><ref name=alsjreturn>{{cite web|title=Return to Earth|url=http://www.hq.nasa.gov/alsj/a17/a17.homeward.html|publisher=NASA|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 17 Lunar Surface Journal|access-date=August 22, 2011|archive-date=May 8, 2012|archive-url=https://web.archive.org/web/20120508061739/http://www.hq.nasa.gov/alsj/a17/a17.homeward.html|url-status=live}}</ref> At 6:35&nbsp;p.m. EST on December{{nbsp}}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 [[trans-Earth injection]] SPS burn lasted just over two minutes.{{sfn|Orloff & Harland 2006|p=518}}

During the return to Earth, Evans performed a 65-minute EVA to retrieve film cassettes from the service module's SIM bay, with assistance from Schmitt who remained at the command module's hatch. At approximately 160,000 nautical miles<ref>{{cite web |url=https://www.hq.nasa.gov/alsj/a17/AS17_PAO.PDF |archive-url=https://ghostarchive.org/archive/20221009/https://www.hq.nasa.gov/alsj/a17/AS17_PAO.PDF |archive-date=2022-10-09 |url-status=live |title=Apollo 17 Transcripts: Apollo 17 (PAO) Spacecraft Commentary |publisher=NASA|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 17 Lunar Surface Journal}}</ref>{{rp|1730}} (184,000&nbsp;mi; 296,000&nbsp;km) from Earth, it was the third "deep space" EVA in history, performed at great distance from any planetary body. As of {{YEAR}}, 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.<ref name=astronautix/><ref name="Drew">{{cite web |url=https://www.drewexmachina.com/2017/12/17/a-history-of-deep-space-evas/ |title=A History of Deep Space EVAs |last=LePage |first=Andrew |date=December 17, 2017 |website=Drew Ex Machina |access-date=January 5, 2022 |archive-date=November 6, 2019 |archive-url=https://web.archive.org/web/20191106041314/https://www.drewexmachina.com/2017/12/17/a-history-of-deep-space-evas/ |url-status=live }}</ref>

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.{{sfn|Orloff & Harland 2006|p=520}} On December 19, the crew jettisoned the no-longer-needed SM, leaving only the CM for return to Earth. The Apollo 17 spacecraft [[Atmospheric entry|reentered Earth's atmosphere]] and splashed down safely in the [[Pacific Ocean]] at 2:25&nbsp;p.m. EST, {{convert|6.4|km|mi|sp=us}} from the recovery ship, {{USS|Ticonderoga|CV-14|6}}. Cernan, Evans, and Schmitt were then retrieved by a recovery helicopter piloted by Commander Edward E. Dahill, III and were safe aboard the recovery ship 52 minutes after splashdown.<ref name=astronautix/><ref name=alsjreturn/><ref>{{cite news |title=Obituaries – Commander Edward E. "Ted" Dahill, III (ret.) |newspaper=Coronado Eagle and Journal |url=https://cdnc.ucr.edu/cgi-bin/cdnc?a=d&d=CJ20070509.2.84&e=-------en--20--1--txt-txIN--------1 |access-date=March 14, 2022 |date=May 9–15, 2007 |archive-date=March 14, 2022 |archive-url=https://web.archive.org/web/20220314215124/https://cdnc.ucr.edu/cgi-bin/cdnc?a=d&d=CJ20070509.2.84&e=-------en--20--1--txt-txIN--------1 |url-status=live }}</ref> 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.{{sfn|Chaikin 1995|p=550}}