Editing Apollo 16 (section)

==Mission events==
Elements of the spacecraft and launch vehicle began arriving at [[Kennedy Space Center]] in July 1970, and all had arrived by September 1971. Apollo 16 was originally scheduled to launch on March 17, 1972. One of the bladders for the CM's [[reaction control system]] burst during testing. This issue, in combination with concerns that one of the explosive cords that would jettison the LM from the CSM after the astronauts returned from the lunar surface would not work properly, and a problem with Duke's spacesuit, made it desirable to slip the launch to the next [[launch window]]. Thus, Apollo 16 was postponed to April 16. The launch vehicle stack, which had been rolled out from the [[Vehicle Assembly Building]] on December 13, 1971, was returned thereto on January 27, 1972. It was rolled out again to [[Launch Complex 39A]] on February 9.<ref name = "launch">{{cite web|title=Day One Part One: Launch and Reaching Earth Orbit|date=February 7, 2020|access-date=September 23, 2021|editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt|publisher=[[NASA]]|url=https://history.nasa.gov/afj/ap16fj/01_Day1_Pt1.html|work=Apollo 16 Flight Journal|archive-date=January 26, 2012|archive-url=https://web.archive.org/web/20120126150006/http://history.nasa.gov/ap16fj/01_Day1_Pt1.htm|url-status=live}}</ref>

The official mission countdown began on Monday, April 10, 1972, at 8:30&nbsp;am, six days before the launch. At this point the Saturn{{nbsp}}V rocket's three stages were powered up, and drinking water was pumped into the spacecraft. As the countdown began, the crew of Apollo 16 was participating in final training exercises in anticipation of a launch on April 16. The astronauts underwent their final preflight physical examination on April 11.<ref>{{cite news|title=Countdown Begins For Apollo 16 Moon Expedition|url=https://news.google.com/newspapers?id=dbBfAAAAIBAJ&pg=2591,2440343&dq=apollo+16&hl=en|access-date=November 27, 2011|agency=[[Associated Press]]|newspaper=[[Lewiston Morning Tribune]]|date=April 11, 1972|archive-date=February 1, 2022|archive-url=https://web.archive.org/web/20220201050055/https://news.google.com/newspapers?id=dbBfAAAAIBAJ&pg=2591%2C2440343&dq=apollo+16&hl=en|url-status=live}}</ref> The only holds in the countdown were the ones pre-planned in the schedule, and the weather was fair as the time for launch approached.{{sfn|Orloff & Harland 2006|p=473}}

===Launch and outward journey===
[[File:Apollo 16 lift-off.jpg|thumb|right|upright=1.3|Launch of Apollo 16]]
The Apollo 16 mission launched from the Kennedy Space Center in Florida at 12:54&nbsp;pm EST on April 16, 1972.<ref name=launch /> The launch was nominal; the crew experienced vibration similar to that on previous missions. The first and second stages of the Saturn{{nbsp}}V (the S-IC and [[S-II]]) performed nominally; the spacecraft entered [[Low Earth orbit|orbit]] around Earth just under 12 minutes after lift-off.

After reaching orbit, the crew spent time adapting to the [[weightlessness|zero-gravity]] environment and preparing the spacecraft for [[trans-lunar injection]] (TLI), the burn of the third-stage rocket that would propel them to the Moon. In Earth orbit, the crew faced minor technical issues, including a potential problem with the environmental control system and the [[S-IVB]] third stage's attitude control system, but eventually resolved or compensated for them as they prepared to depart towards the Moon.

After two orbits, the rocket's third stage reignited for just over five minutes, propelling the craft towards the Moon at about {{convert|22000|mph|km/h|abbr=on|order=flip}}.<ref>{{cite web|title=Apollo 16: Day One Part Three: Second Earth Orbit and Translunar Injection|date=May 8, 2006|url=https://history.nasa.gov/ap16fj/03_Day1_Pt3.htm|work=Apollo 16 Flight Journal|publisher=[[NASA]]|archive-url=https://web.archive.org/web/20111021204204/http://history.nasa.gov/ap16fj/03_Day1_Pt3.htm|archive-date=October 21, 2011|url-status=dead|editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt}}</ref> Six minutes after the burn of the S-IVB, the command and service modules (CSM), containing the crew, separated from the rocket and traveled {{convert|15|m|ft|abbr=on|sp=us|order=flip}} away from it before turning around and retrieving the lunar module from inside the expended rocket stage. The maneuver, performed by Mattingly and known as [[transposition, docking, and extraction]], went smoothly.<ref>{{cite web|title=Apollo 16: Day One Part Four: Transposition, Docking and Ejection|url=https://history.nasa.gov/afj/ap16fj/03_Day1_Pt3.html|work=Apollo 16 Flight Journal|date=February 7, 2020|access-date=September 23, 2021|editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt|publisher=[[NASA]]|archive-date=October 23, 2012|archive-url=https://web.archive.org/web/20121023155334/http://history.nasa.gov/ap16fj/03_Day1_Pt3.htm|url-status=live}}</ref><ref name="fullsummary">{{cite web|title=Apollo 16 Flight Summary|url=https://history.nasa.gov/afj/ap16fj/a16summary.html|work=Apollo 16 Flight Journal|date=January 19, 2019|access-date=November 27, 2011|editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt|publisher=[[NASA]]|archive-date=July 21, 2019|archive-url=https://web.archive.org/web/20190721143418/https://history.nasa.gov/afj/ap16fj/a16summary.html|url-status=live}}</ref>

Following transposition and docking, the crew noticed the exterior surface of the Lunar Module was giving off particles from a spot where the LM's skin appeared torn or shredded; at one point, Duke estimated they were seeing about five to ten particles per second. Young and Duke entered the Lunar Module through the docking tunnel connecting it with the command module to inspect its systems, at which time they did not spot any major issues.

Once on course towards the Moon, the crew put the spacecraft into a rotisserie "barbecue" mode in which the craft rotated along its long axis three times per hour to ensure even heat distribution about the spacecraft from the Sun. After further preparing the craft for the voyage, the crew began the first sleep period of the mission just under 15 hours after launch.<ref>{{cite web|title=Apollo 16: Day 1 Part 5: Settling into Translunar Coast|url=https://history.nasa.gov/afj/ap16fj/05_Day1_Pt5.html|work=Apollo 16 Flight Journal|date=February 7, 2020|access-date=September 23, 2021|editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt|publisher=[[NASA]]|archive-date=October 28, 2012|archive-url=https://web.archive.org/web/20121028074016/http://history.nasa.gov/ap16fj/05_Day1_Pt5.htm|url-status=live}}</ref>
[[File:AS16-118-18885.jpg|left|thumb|upright=1.3|Earth from Apollo 16 during the trans-lunar coast, showing the US at center]]
By the time [[Christopher C. Kraft Jr. Mission Control Center|Mission Control]] issued the wake-up call to the crew for flight day two, the spacecraft was about {{convert|98000|nmi|km|sp=us|order=flip}} away from the Earth, traveling at about {{convert|5322|ft/s|km/s|abbr=on|sp=us|order=flip}}. As it was not due to arrive in lunar orbit until flight day four,<ref name=moonarrival>{{cite web|title=Apollo 16: Day Four Part One – Arrival at the Moon|url=https://history.nasa.gov/afj/ap16fj/10_Day4_Pt1.html|work=Apollo 16 Flight Journal|date=February 7, 2020|access-date=September 23, 2021|editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt|publisher=[[NASA]]|archive-date=October 21, 2012|archive-url=https://web.archive.org/web/20121021002834/http://history.nasa.gov/ap16fj/10_Day4_Pt1.htm|url-status=live}}</ref> flight days two and three were largely preparatory, consisting of spacecraft maintenance and scientific research. On day two, the crew performed an [[electrophoresis]] experiment, also performed on Apollo 14,<ref name = "two" /> in which they attempted to demonstrate that electrophoretic separation in their near-weightless environment could be used to produce substances of greater purity than would be possible on Earth. Using two different sizes of [[polystyrene]] particles, one size colored red and one blue, separation of the two types via electrophoresis was achieved, though electro-osmosis in the experiment equipment prevented the clear separation of two particle bands.{{sfn|Press Kit|p=103}}<ref>{{cite web|first=R.S.|last=Snyder|title=Electrophoresis Demonstration on Apollo 16|publisher=[[NASA]]|date=November 1972|url=https://ntrs.nasa.gov/api/citations/19730009430/downloads/19730009430.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://ntrs.nasa.gov/api/citations/19730009430/downloads/19730009430.pdf |archive-date=2022-10-09 |url-status=live|pages=30–32}}</ref>

The remainder of day two included a two-second mid-course correction burn performed by the CSM's [[service propulsion system]] (SPS) engine to tweak the spacecraft's trajectory. Later in the day, the astronauts entered the Lunar Module for the second time to further inspect the landing craft's systems. The crew reported they had observed additional paint peeling from a portion of the LM's outer aluminum skin. Despite this, the crew discovered that the spacecraft's systems were performing nominally. Following the LM inspection, the crew reviewed checklists and procedures for the following days in anticipation of their arrival and the [[Lunar orbit|Lunar Orbit Insertion]] (LOI) burn. Command Module Pilot Mattingly reported "[[gimbal lock]]", meaning that the system to keep track of the craft's [[attitude (aircraft)|attitude]] was no longer accurate. Mattingly had to realign the guidance system using the Sun and Moon. At the end of day two, Apollo 16 was about {{convert|140000|nmi|km|order=flip|sp=us}} away from Earth.<ref name = "two" >{{cite web|title=Apollo 16: Day Two Part Two: LM Entry and Checks|url=https://history.nasa.gov/ap16fj/07_Day2_Pt2.htm|work=Apollo 16 Flight Journal|archive-url=https://web.archive.org/web/20111021203814/http://history.nasa.gov/ap16fj/07_Day2_Pt2.htm|archive-date=October 21, 2011|url-status=dead|editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt|publisher=[[NASA]]}}</ref>

When the astronauts were awakened for flight day three, the spacecraft was about {{convert|157000|nmi|km|sp=us|order=flip}} away from the Earth. The velocity of the craft steadily decreased, as it had not yet reached the lunar sphere of gravitational influence. The early part of day three was largely housekeeping, spacecraft maintenance and exchanging status reports with Mission Control in Houston. The crew performed the Apollo light flash experiment, or ALFMED, to investigate "light flashes" that were seen by Apollo lunar astronauts when the spacecraft was dark, regardless of whether their eyes were open. This was thought to be caused by the penetration of the [[Human eye|eye]] by [[cosmic ray]] particles.<ref>{{cite web|title=Apollo 16: Day Three Part One: ALFMED Experiment|url=https://history.nasa.gov/ap16fj/08_Day3_Pt1.htm|work=Apollo 16 Flight Journal|archive-url=https://web.archive.org/web/20111021203834/http://history.nasa.gov/ap16fj/08_Day3_Pt1.htm|archive-date=October 21, 2011|url-status=dead|editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt|publisher=[[NASA]]}}</ref><ref name=alfmed>{{cite web|title=Apollo Light Flash Investigations (AP009)|url=http://lsda.jsc.nasa.gov/scripts/experiment/exper.aspx?exp_index=380|work=Life Sciences Data Archive|publisher=[[NASA]]|access-date=July 22, 2013|archive-date=December 31, 2020|archive-url=https://web.archive.org/web/20201231213212/https://lsda.jsc.nasa.gov/Experiment/exper/380|url-status=live}}</ref> During the second half of the day, Young and Duke again entered the Lunar Module to power it up and check its systems, and perform housekeeping tasks in preparation for the lunar landing. The systems were found to be functioning as expected. Following this, the crew donned their space suits and rehearsed procedures that would be used on landing day. Just before the end of flight day three at 59 hours, 19 minutes, 45 seconds after liftoff, while {{convert|178673|nmi|km|sp=us|order=flip}} from the Earth and {{convert|33821|nmi|km|sp=us|order=flip}} from the Moon, the spacecraft's velocity began increasing as it accelerated towards the Moon after entering the lunar sphere of influence.<ref>{{cite web|title=Apollo 16: Day Three Part Two: Lunar Module Activation and Checkout|url=https://history.nasa.gov/ap16fj/09_Day3_Pt2.htm|work=Apollo 16 Flight Journal|archive-url=https://web.archive.org/web/20111021204136/http://history.nasa.gov/ap16fj/09_Day3_Pt2.htm|archive-date=October 21, 2011|url-status=dead|editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt|publisher=[[NASA]]}}</ref>

After waking up on flight day four, the crew began preparations for the LOI maneuver that would brake them into orbit.<ref name="moonarrival"/> At an altitude of {{convert|11142|nmi|km|sp=us|order=flip}} the [[scientific instrument module]] (SIM) bay cover was jettisoned. At just over 74 hours into the mission, the spacecraft passed behind the Moon, temporarily losing contact with Mission Control. While over the [[far side of the Moon|far side]], the SPS burned for 6{{nbsp}}minutes and 15 seconds, braking the spacecraft into an orbit with a low point (pericynthion) of 58.3 and a high point (apocynthion) of 170.4 nautical miles (108.0 and 315.6&nbsp;km, respectively).<ref>{{cite web|title=Apollo 16: Day Four Part Two; Lunar Orbit Insertion, Rev One and Rev Two|url=https://history.nasa.gov/ap16fj/11_Day4_Pt2.htm|work=Apollo 16 Flight Journal|archive-url=https://web.archive.org/web/20111021203744/http://history.nasa.gov/ap16fj/11_Day4_Pt2.htm|archive-date=October 21, 2011|url-status=dead|editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt|publisher=[[NASA]]}}</ref> After entering lunar orbit, the crew began preparations for the Descent Orbit Insertion (DOI) maneuver to further modify the spacecraft's orbital trajectory. The maneuver decreased the craft's pericynthion to {{convert|10.7|nmi|km|sp=us|order=flip}}. The remainder of flight day four was spent making observations and preparing for activation of the Lunar Module, undocking, and landing the following day.<ref>{{cite web|title=Apollo 16: Day Four Part Three: Descent Orbit Insertion, Revs Three to Nine|url=https://history.nasa.gov/ap16fj/12_Day4_Pt3.htm|work=Apollo 16 Flight Journal|archive-url=https://web.archive.org/web/20111021155928/http://history.nasa.gov/ap16fj/12_Day4_Pt3.htm|archive-date=October 21, 2011|url-status=dead|editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt|publisher=[[NASA]]}}</ref>

===Lunar surface===
[[File:Apollo 16 meeting.jpg|thumb|right|NASA officials conferring on whether to allow the Apollo 16 landing, April 20, 1972]]

The crew continued preparing for Lunar Module activation and undocking shortly after waking up to begin flight day five. The boom that extended the [[mass spectrometry|mass spectrometer]] in the SIM bay was stuck, semi-deployed. It was decided that Young and Duke would visually inspect the boom after undocking the LM from the CSM. They entered the LM for activation and checkout of the spacecraft's systems. Despite entering the LM 40 minutes ahead of schedule, they completed preparations only 10 minutes early due to numerous delays in the process.<ref name="fullsummary" /> With the preparations finished, they undocked 96 hours, 13 minutes, 31 seconds into the mission.<ref>{{cite web|title=Apollo 16: Day Five Part Two: Lunar Module Undocking and Descent Preparation; Revs 11 and 12|url=https://history.nasa.gov/ap16fj/14_Day5_Pt2.htm|work=Apollo 16 Flight Journal|archive-url=https://web.archive.org/web/20111021160435/http://history.nasa.gov/ap16fj/14_Day5_Pt2.htm|archive-date=October 21, 2011|url-status=dead|editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt|publisher=[[NASA]]}}</ref><ref name="timeline">{{cite web |url=https://history.nasa.gov/SP-4029/Apollo_16i_Timeline.htm |title=Apollo 16 Timeline |publisher=[[NASA]] |access-date=October 8, 2019 |archive-date=December 31, 2020 |archive-url=https://web.archive.org/web/20201231213215/https://history.nasa.gov/SP-4029/Apollo_16i_Timeline.htm |url-status=live }}</ref>

For the rest of the two crafts' passes over the [[near side of the Moon]], Mattingly prepared to shift ''Casper'' to a higher, near-circular orbit, while Young and Duke prepared ''Orion'' for the descent to the lunar surface. At this point, during tests of the CSM's steerable rocket engine in preparation for the burn to modify the craft's orbit, Mattingly detected oscillations in the SPS engine's backup gimbal system. According to mission rules, under such circumstances, ''Orion'' was to re-dock with ''Casper'', in case Mission Control decided to abort the landing and use the Lunar Module's engines for the return trip to Earth. Instead, the two craft [[Orbital station-keeping|kept station]], maintaining positions close to each other. After several hours of analysis, mission controllers determined that the malfunction could be worked around, and Young and Duke could proceed with the landing.<ref name="overview" />

Powered descent to the lunar surface began about six hours behind schedule. Because of the delay, Young and Duke began their descent to the surface at an altitude higher than that of any previous mission, at {{convert|20.1|km|nmi|sp=us}}. After descending to an altitude of about {{convert|4000|m|ft|abbr=on|sp=us|order=flip}}, Young was able to view the landing site in its entirety. Throttle-down of the LM's landing engine occurred on time, and the spacecraft tilted forward to its landing orientation at an altitude of {{convert|2200|m|ft|abbr=on|sp=us|order=flip}}. The LM landed {{convert|270|m|ft|abbr=on|sp=us|order=flip}} north and {{convert|60|m|ft|abbr=on|sp=us|order=flip}} west of the planned landing site at 104 hours, 29 minutes, and 35 seconds into the mission, at 2:23:35 UTC on April 21 (8:23:35&nbsp;pm on April 20 in Houston).<ref name="fullsummary" /><ref name="landing">{{cite web|title=Landing at Descartes|date=December 9, 2015|url=http://www.hq.nasa.gov/alsj/a16/a16.landing.html|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 16 Lunar Surface Journal|access-date=September 23, 2021|archive-date=December 31, 2020|archive-url=https://web.archive.org/web/20201231213219/https://www.hq.nasa.gov/alsj/a16/a16.landing.html|url-status=live}}</ref> The availability of the [[Lunar Roving Vehicle]] rendered their distance from the targeted point trivial.<ref name="overview" />

After landing, Young and Duke began powering down some of the LM's systems to conserve battery power. Upon completing their initial procedures, the pair configured ''Orion'' for their three-day stay on the lunar surface, removed their space suits and took initial geological observations of the immediate landing site. They then settled down for their first meal on the surface. After eating, they configured the cabin for sleep.<ref>{{cite web|title=Post-Landing Activities|url=http://www.hq.nasa.gov/alsj/a16/a16.postland.html|date=July 21, 2015|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 16 Lunar Surface Journal|access-date=September 23, 2021|archive-date=December 31, 2020|archive-url=https://web.archive.org/web/20201231213248/https://www.hq.nasa.gov/alsj/a16/a16.postland.html|url-status=live}}</ref><ref>{{cite web|title=Window Geology|url=http://www.hq.nasa.gov/alsj/a16/a16.window.html|date=May 29, 2012|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 16 Lunar Surface Journal|access-date=September 23, 2021|archive-date=December 31, 2020|archive-url=https://web.archive.org/web/20201231213220/https://www.hq.nasa.gov/alsj/a16/a16.window.html|url-status=live}}</ref> The landing delay caused by the malfunction in the CSM's main engine necessitated significant modifications to the mission schedule. Apollo 16 would spend one less day in lunar orbit after surface exploration had been completed to afford the crew ample margins in the event of further problems. In order to improve Young's and Duke's sleep schedule, the third and final moonwalk of the mission was trimmed from seven hours to five.<ref name="fullsummary" />

==== First moonwalk ====
After waking up on April 21, Young and Duke ate breakfast and began preparations for the first extravehicular activity (EVA), or moonwalk.<ref>{{cite web|title=Wake-up for EVA-1|date=November 22, 2009|url=http://www.hq.nasa.gov/alsj/a16/a16.eva1wake.html|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 16 Lunar Surface Journal|access-date=September 23, 2021|archive-date=December 31, 2020|archive-url=https://web.archive.org/web/20201231213246/https://www.hq.nasa.gov/alsj/a16/a16.eva1wake.html|url-status=live}}</ref><ref>{{cite web|title=Preparations for EVA-1|date=September 22, 2014|url=http://www.hq.nasa.gov/alsj/a16/a16.eva1prep.html|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 16 Lunar Surface Journal|access-date=September 23, 2021|archive-date=February 1, 2022|archive-url=https://web.archive.org/web/20220201050321/https://www.hq.nasa.gov/alsj/a16/a16.eva1prep.html|url-status=live}}</ref> After the pair donned and pressurized their space suits and depressurized the Lunar Module cabin, Young climbed out onto the "porch" of the LM, a small platform above the ladder. Duke handed Young a jettison bag full of trash to dispose of on the surface.<ref name="briar">{{cite web|title=Back in the Briar Patch|url=http://www.hq.nasa.gov/alsj/a16/a16.eva1prelim.html|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 16 Lunar Surface Journal|date=December 7, 2012|access-date=September 23, 2021|archive-date=December 31, 2020|archive-url=https://web.archive.org/web/20201231213221/https://www.hq.nasa.gov/alsj/a16/a16.eva1prelim.html|url-status=live}}</ref> Young then lowered the equipment transfer bag (ETB), containing equipment for use during the EVA, to the surface. Young descended the ladder and, upon setting foot on the lunar surface, became the ninth human to walk on the Moon.<ref name="fullsummary" /> Upon stepping onto the surface, Young expressed his sentiments about being there: "There you are: Mysterious and unknown Descartes. Highland plains. Apollo 16 is gonna change your image. I'm sure glad they got ol' [[Brer Rabbit]], here, back in the briar patch where he belongs."<ref name="briar" /> Duke soon descended the ladder and joined Young on the surface, becoming the tenth person to walk on the Moon. Duke was then aged 36; no younger human has ever walked on the lunar surface. Duke expressed his excitement, stating to CAPCOM Anthony England: "Fantastic! Oh, that first foot on the lunar surface is super, Tony!"<ref name="briar" /> The pair's first task of the moonwalk was to offload the Lunar Roving Vehicle, the Far Ultraviolet Camera/Spectrograph,<ref>{{cite web|title=Experiment Operations During Apollo EVAs |url=http://ares.jsc.nasa.gov/HumanExplore/Exploration/EXlibrary/docs/ApolloCat/Part1/UVC.htm |work=[[Astromaterials Research and Exploration Science Directorate]] |publisher=[[NASA]] |url-status=dead |archive-url=https://web.archive.org/web/20130220145727/http://ares.jsc.nasa.gov/HumanExplore/Exploration/EXLibrary/docs/ApolloCat/Part1/UVC.htm |archive-date=February 20, 2013 }}</ref> and other equipment. This was done without problems. On first driving the lunar rover, Young discovered that the rear steering was not working. He alerted Mission Control to the problem before setting up the television camera, after which Duke erected the United States [[Lunar Flag Assembly|flag]]. During lunar surface operations, Commander Young always drove the rover, while Lunar Module Pilot Duke assisted with navigation; this was a division of responsibilities 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|date=November 6, 2012|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 15 Lunar Surface Journal|access-date=March 2, 2020|archive-date=February 20, 2022|archive-url=https://web.archive.org/web/20220220212002/https://www.hq.nasa.gov/alsj/a15/a15.summary.html|url-status=live}}</ref><ref name="Haynes">{{cite book |title=Lunar Rover: Owner's Workshop Manual |last1=Riley |first1=Christopher |last2=Woods |first2=David |last3=Dolling |first3=Philip |date=December 2012 |publisher=[[Haynes Manual|Haynes]] |isbn=978-0-85733-267-7 |page=165}}</ref>

[[File:Ap16 rover.ogv|thumb|left|Young driving the LRV during the "Grand Prix"]]
The day's next task was to deploy the ALSEP; while they were parking the lunar rover, on which the TV camera was mounted, to observe the deployment, the rear steering began functioning. After ALSEP deployment, they collected samples in the vicinity. About four hours after the beginning of EVA-1, they mounted the lunar rover and drove to the first geologic stop, Plum Crater, a {{convert|36|m|ft|abbr=on|adj=mid|-wide|order=flip}} crater on the rim of [[Flag (crater)|Flag Crater]], about {{convert|240|m|ft|abbr=on|sp=us}} across. There, at a distance of {{convert|1.4|km|mi|abbr=on|sp=us}} from the LM, they sampled material in the vicinity, which scientists believed had penetrated through the upper regolith layer to the underlying [[Cayley (crater)|Cayley Formation]]. It was there that Duke retrieved, at the request of Mission Control, the largest rock returned by an Apollo mission, a [[breccia]] nicknamed [[Big Muley]] after mission geology principal investigator [[William R. Muehlberger]].<ref name="honeysuckle">{{cite web |url=http://www.honeysucklecreek.net/msfn_missions/Apollo_16_mission/hl_apollo16.html |title=Apollo 16 |last=Lindsay |first=Hamish |publisher=[[Honeysuckle Creek Tracking Station]] |type=Essay |access-date=November 27, 2011 |archive-date=December 31, 2020 |archive-url=https://web.archive.org/web/20201231213249/https://www.honeysucklecreek.net/msfn_missions/Apollo_16_mission/hl_apollo16.html |url-status=live }}</ref><ref>{{cite web|title=Station 1 at Plum Crater|date=April 7, 2018|url=https://www.hq.nasa.gov/alsj/a16/a16.sta1.html|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 16 Lunar Surface Journal|access-date=September 23, 2021|archive-date=February 25, 2021|archive-url=https://web.archive.org/web/20210225171542/https://www.hq.nasa.gov/alsj/a16/a16.sta1.html|url-status=live}}</ref> The next stop of the day was Buster Crater, a small crater located north of the larger [[Spook (crater)|Spook Crater]], about {{convert|1.6|km|mi|abbr=on}} from the LM. There, Duke took pictures of Stone Mountain and South Ray Crater, while Young deployed the LPM.<ref>{{cite web|title=Station 2 at Buster Crater|date=July 18, 2011|url=http://next.nasa.gov/alsj/a16/a16.sta2.html|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 16 Lunar Surface Journal|url-status=dead|archive-url=https://web.archive.org/web/20111025113946/http://next.nasa.gov/alsj/a16/a16.sta2.html|archive-date=October 25, 2011}}</ref> By this point, scientists were beginning to reconsider their pre-mission hypothesis that Descartes had been the setting of ancient volcanic activity, as the two astronauts had yet to find any volcanic material. Following their stop at Buster, Young did a "Grand Prix" demonstration drive of the lunar rover, which Duke filmed with a [[16 mm film|16 mm]] movie camera. This had been attempted on Apollo 15, but the camera had malfunctioned.<ref>{{cite web|title=Grand Prix|url=http://next.nasa.gov/alsj/a16/a16.trvlm1.html|date=January 17, 2020|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 16 Lunar Surface Journal|url-status=dead|archive-url=https://web.archive.org/web/20111026114051/http://next.nasa.gov/alsj/a16/a16.trvlm1.html|archive-date=October 26, 2011}}</ref> After completing more tasks at the ALSEP, they returned to the LM to close out the moonwalk. They reentered the LM 7{{nbsp}}hours, 6{{nbsp}}minutes, and 56 seconds after the start of the EVA. Once inside, they pressurized the LM cabin, went through a half-hour debriefing with scientists in Mission Control, and configured the cabin for the sleep period.<ref name="honeysuckle" /><ref>{{cite web|title=EVA-1 Closeout|url=http://next.nasa.gov/alsj/a16/a16.clsout1.html|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 16 Lunar Surface Journal|url-status=dead|archive-url=https://web.archive.org/web/20111024214907/http://next.nasa.gov/alsj/a16/a16.clsout1.html|archive-date=October 24, 2011}}</ref><ref>{{cite web|title=Debrief and Goodnight|url=http://next.nasa.gov/alsj/a16/a16.debrief1.html|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 16 Lunar Surface Journal|url-status=dead|archive-url=https://web.archive.org/web/20111021105620/http://next.nasa.gov/alsj/a16/a16.debrief1.html|archive-date=October 21, 2011|date=June 18, 2011}}</ref>

==== Second moonwalk ====
[[File:Young and Rover on the Descartes - GPN-2000-001133.jpg|thumb|upright=1.3|right|The view from the side of Stone Mountain, which Duke described as "spectacular"<ref name=station4/>]]

Waking up three and a half minutes earlier than planned, they discussed the day's timeline of events with Houston.<ref>{{cite web|title=EVA-2 Wake-up|url=http://next.nasa.gov/alsj/a16/a16.eva2wake.html|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 16 Lunar Surface Journal|url-status=dead|archive-url=https://web.archive.org/web/20111017000524/http://next.nasa.gov/alsj/a16/a16.eva2wake.html|archive-date=October 17, 2011|date=January 15, 2006}}</ref><ref>{{cite web|title=Preparations for EVA-2|url=http://next.nasa.gov/alsj/a16/a16.eva2prep.html|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 16 Lunar Surface Journal|url-status=dead|archive-url=https://web.archive.org/web/20111021105700/http://next.nasa.gov/alsj/a16/a16.eva2prep.html|archive-date=October 21, 2011|date=May 9, 2010}}</ref> The second lunar excursion's primary objective was to visit Stone Mountain to climb up the slope of about 20 degrees to reach a cluster of five craters known as "[[Cinco (crater)|Cinco craters]]". They drove there in the LRV, traveling {{convert|3.8|km|mi|abbr=on|sp=us}} from the LM. At {{convert|152|m|ft|abbr=on|sp=us}} above the valley floor, the pair were at the highest elevation above the LM of any Apollo mission. They marveled at the view (including South Ray) from the side of Stone Mountain, which Duke described as "spectacular",<ref name=station4>{{cite web|title=Geology Station 4 at the Stone Mountain Cincos|url=http://next.nasa.gov/alsj/a16/a16.sta4.html|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 16 Lunar Surface Journal|url-status=dead|archive-url=https://web.archive.org/web/20111025050902/http://next.nasa.gov/alsj/a16/a16.sta4.html|archive-date=October 25, 2011|date=July 19, 2011}}</ref> then gathered samples in the vicinity.<ref name=honeysuckle/> After spending 54 minutes on the slope, they climbed aboard the lunar rover en route to the day's second stop, dubbed Station 5, a crater {{convert|20|m|ft|abbr=on}} across. There, they hoped to find Descartes material that had not been contaminated by ejecta from South Ray Crater, a large crater south of the landing site. The samples they collected there, despite still uncertain origin, are according to geologist Wilhelms, "a reasonable bet to be Descartes".<ref name=honeysuckle/>

The next stop, Station 6, was a {{convert|10|m|ft|abbr=on|adj=mid|-wide|sp=us}} blocky crater, where the astronauts believed they could sample the Cayley Formation as evidenced by the firmer soil found there. Bypassing station seven to save time, they arrived at Station 8 on the lower flank of Stone Mountain, where they sampled material on a ray from South Ray crater for about an hour. There, they collected black and white breccias and smaller, [[crystal]]line rocks rich in [[plagioclase]]. At Station 9, an area known as the "Vacant Lot",<ref>{{cite web|title=Geology Station 9|url=https://www.hq.nasa.gov/alsj/a16/a16.sta9.html|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 16 Lunar Surface Journal|access-date=September 23, 2021|date=May 1, 2018|archive-date=June 8, 2021|archive-url=https://web.archive.org/web/20210608152734/https://www.hq.nasa.gov/alsj/a16/a16.sta9.html|url-status=live}}</ref> which was believed to be free of ejecta from South Ray, they spent about 40 minutes gathering samples. Twenty-five minutes after departing the Vacant Lot, they arrived at the final stop of the day, halfway between the ALSEP site and the LM. There, they dug a double core and conducted several [[penetrometer]] tests along a line stretching {{convert|50|m|ft|abbr=on}} east of the ALSEP. At the request of Young and Duke, the moonwalk was extended by ten minutes. After returning to the LM to wrap up the second lunar excursion, they climbed back inside the landing craft's cabin, sealing and pressurizing the interior after 7{{nbsp}}hours, 23 minutes, and 26 seconds of EVA time, breaking a record that had been set on Apollo 15.<ref name="honeysuckle" /><ref>{{cite web|title=EVA-2 Closeout|url=http://next.nasa.gov/alsj/a16/a16.clsout2.html|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 16 Lunar Surface Journal|url-status=dead|archive-url=https://web.archive.org/web/20111026042001/http://next.nasa.gov/alsj/a16/a16.clsout2.html|archive-date=October 26, 2011|date=July 28, 2011}}</ref> After eating a meal and proceeding with a debriefing on the day's activities with Mission Control, they reconfigured the LM cabin and prepared for the sleep period.<ref>{{cite web|title=Post-EVA-2 Activities and Goodnight|url=http://next.nasa.gov/alsj/a16/a16.eva2post.html|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 16 Lunar Surface Journal|url-status=dead|archive-url=https://web.archive.org/web/20120425231519/http://next.nasa.gov/alsj/a16/a16.eva2post.html|archive-date=April 25, 2012|date=September 25, 2011}}</ref>

==== Third moonwalk ====
[[File:JSC2007e045382.jpg|thumb|upright=1.8|left|John Young adjusting the LRV's antenna near Shadow Rock]]

Flight day seven was their third and final day on the lunar surface, returning to orbit to rejoin Mattingly in the CSM following the day's moonwalk. During the third and final lunar excursion, they were to explore [[North Ray (crater)|North Ray]] crater, the largest of any of the craters any Apollo expedition had visited. After exiting ''Orion'', the pair drove to North Ray crater. The drive was smoother than that of the previous day, as the craters were shallower and boulders were less abundant north of the immediate landing site. After passing [[Palmetto (crater)|Palmetto]] crater, boulders gradually became larger and more abundant as they approached North Ray in the lunar rover. Upon arriving at the rim of North Ray crater, they were {{convert|4.4|km|mi|abbr=on|sp=us}} away from the LM. After their arrival, the duo took photographs of the {{convert|1|km|mi|abbr=on|sp=us}} wide and {{convert|230|m|ft|abbr=on|sp=us}} deep crater. They visited a large boulder, taller than a four-story building, which became known as 'House Rock'. Samples obtained from this boulder delivered the final blow to the pre-mission volcanic hypothesis, proving it incorrect. House Rock had numerous bullet hole-like marks where [[micrometeoroid]]s from space had impacted the rock.<ref name = "honeysuckle" />

About 1{{nbsp}}hour and 22 minutes after arriving at the North Ray crater, they departed for Station 13, a large boulder field about {{convert|0.5|km|mi|abbr=on|sp=us}} from North Ray. On the way, they set a lunar speed record, traveling at an estimated {{convert|17.1|km/h|mph|sp=us}} downhill. They arrived at a {{convert|3|m|ft|abbr=on|sp=us}} high boulder, which they called "Shadow Rock". Here, they sampled permanently shadowed soil. During this time, Mattingly was preparing the CSM in anticipation of their return approximately six hours later. After three hours and six minutes, they returned to the LM, where they completed several experiments and unloaded the rover. A short distance from the LM, Duke placed a photograph of his family and an Air Force commemorative medallion on the surface.<ref name="honeysuckle" /> Young drove the rover to a point about {{convert|90|m|ft|abbr=on|sp=us}} east of the LM, known as the 'VIP site,' so its television camera, controlled remotely by Mission Control, could observe Apollo 16's liftoff from the Moon. They then reentered the LM after a 5-hour and 40-minute final excursion.<ref>{{cite web|title=VIP Site|url=http://next.nasa.gov/alsj/a16/a16.vip.html|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 16 Lunar Surface Journal|url-status=dead|archive-url=https://web.archive.org/web/20111026075705/http://next.nasa.gov/alsj/a16/a16.vip.html|archive-date=October 26, 2011|date=August 9, 2011}}</ref> After pressurizing the LM cabin, the crew began preparing to return to lunar orbit.<ref>{{cite web|title=Post-EVA-3 Activities|url=http://next.nasa.gov/alsj/a16/a16.eva3post.html|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 16 Lunar Surface Journal|url-status=dead|archive-url=https://web.archive.org/web/20120425231532/http://next.nasa.gov/alsj/a16/a16.eva3post.html|archive-date=April 25, 2012|date=November 23, 2008}}</ref>

===Solo activities===
[[File:Apollo 16 Command and Service Module Over the Moon (9457443889).jpg|thumb|''Casper'' above the Moon]]
After ''Orion'' was cleared for the landing attempt, ''Casper'' maneuvered away, and Mattingly performed a burn that took his spacecraft to an orbit of {{convert|53.1|by|67.8|nmi|order=flip|sp=us}} in preparation for his scientific work.<ref>{{cite web|title=Day Five Part Five – Clearance for PDI – Again – and Landing, Revs 15 and 16.|url=https://history.nasa.gov/afj/ap16fj/17_Day5_Pt5.html#103_21_44|publisher=[[NASA]]|access-date=June 13, 2021|work=Apollo 16 Flight Journal|date=February 11, 2020|editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt|archive-date=February 24, 2013|archive-url=https://web.archive.org/web/20130224213429/http://history.nasa.gov/ap16fj/17_Day5_Pt5.htm#103_21_44|url-status=live}}</ref><ref name="timeline"/> The SM carried a suite of scientific instruments in its SIM bay,{{sfn|Press Kit|p=86}} similar to those carried on Apollo 15.{{sfn|Mission Report|p=5-1}} Mattingly had compiled a busy schedule operating the various SIM bay instruments, one that became even busier once Houston decided to bring Apollo 16 home a day early, as the flight directors sought to make up for lost time.{{sfn|Chaikin 1995|pp=484–485}}

His work was hampered by various malfunctions: when the Panoramic Camera was turned on, it appeared to take so much power from one of the CSM's electrical systems, that it initiated the spacecraft Master Alarm. It was immediately shut off, though later analysis indicated that the drain might have been from the spacecraft's heaters, which came on at the same time.<ref name="overvw">{{cite web|title=Apollo 16 Mission Overview|url=http://www.hq.nasa.gov/alsj/a16/a16ov.html|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 16 Lunar Surface Journal|access-date=June 12, 2021|archive-date=July 21, 2019|archive-url=https://web.archive.org/web/20190721142640/https://www.hq.nasa.gov/alsj/a16/a16ov.html|url-status=live}}</ref> Its work was also hampered by the delay in the beginning of ''Casper''{{'}}s orbital scientific work and the early return to Earth, and by a malfunction resulting in the [[exposure (photography)|overexposure]] of many of the photographs. Nevertheless, it was able to take a photograph of the Descartes area in which ''Orion'' is visible.{{sfn|Mission Report|pp=5-7—5-8}} The Mass Spectrometer boom did not fully retract following its initial extension, as had happened on Apollo 15, though it retracted far enough to allow the SPS engine to be fired safely when ''Casper'' maneuvered away from ''Orion'' before the LM began its Moon landing attempt. Although the Mass Spectrometer was able to operate effectively, it stuck near its fully deployed position prior to the burn that preceded rendezvous, and had to be jettisoned. Scientists had hoped to supplement the lunar data gained with more on the trans-Earth coast, but Apollo 15 data could be used instead.<ref name = "overvw" />{{sfn|Mission Report|p=5-4}} The Mapping Camera also did not function perfectly; later analysis found it to have problems with its glare shield. The changes to the flight plan meant that some areas of the lunar surface that were supposed to be photographed could not be; also, a number of images were overexposed.<ref name = "overvw" />{{sfn|Mission Report|pp=5-10—5-11}} The Laser Altimeter, designed to accurately measure the spacecraft altitude, slowly lost accuracy due to reduced power, and finally failed just before it was due to be used for the last time.<ref name = "overvw" />{{sfn|Mission Report|pp=5-11—5-12}}

===Return to Earth===
[[File:S72-37001.jpg|thumb|Ken Mattingly performing his deep-space [[Extravehicular activity|EVA]], retrieving film cassettes from the CSM's exterior]]
Eight minutes before the planned departure from the lunar surface, CAPCOM [[James Irwin]] notified Young and Duke from Mission Control that they were go for liftoff. Two minutes before launch, they activated the "Master Arm" switch and then the "Abort Stage" button, causing small explosive charges to sever the ascent stage from the [[Apollo Lunar Module#Descent stage|descent stage]], with cables connecting the two severed by a [[guillotine]]-like mechanism. At the pre-programmed moment, there was liftoff and the ascent stage blasted away from the Moon, as the camera aboard the LRV followed the first moments of the flight. Six minutes after liftoff, at a speed of about {{convert|5000|km/h|mph|sp=us}}, Young and Duke reached lunar orbit.<ref name=honeysuckle/><ref>{{cite web|title=Return to Orbit|url=http://www.hq.nasa.gov/alsj/a16/a16.launch.html|publisher=[[NASA]]|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 16 Lunar Surface Journal|access-date=November 29, 2011|archive-date=December 31, 2020|archive-url=https://web.archive.org/web/20201231213251/https://www.hq.nasa.gov/alsj/a16/a16.launch.html|url-status=live}}</ref> Young and Duke rendezvoused and re-docked with Mattingly in the CSM. To minimize the transfer of lunar dust from the LM cabin into the CSM, Young and Duke cleaned the cabin before opening the hatch separating the two spacecraft. After opening the hatch and reuniting with Mattingly, the crew transferred the samples Young and Duke had collected on the surface into the CSM for transfer to Earth. After transfers were completed, the crew would sleep before jettisoning the empty Lunar Module ascent stage the next day, when it was to be crashed intentionally into the lunar surface in order to calibrate the seismometer Young and Duke had left on the surface.<ref name="fullsummary" />

The next day, after final checks were completed, the expended LM ascent stage was jettisoned.<ref name=lmjett>{{cite web|title=Apollo 16: Day 9 Part 2 – LM Jettison and Trans Earth Injection|url=https://history.nasa.gov/ap16fj/25_Day9_Pt2.htm|work=Apollo 16 Flight Journal|archive-url=https://web.archive.org/web/20111021155938/http://history.nasa.gov/ap16fj/25_Day9_Pt2.htm|archive-date=October 21, 2011|url-status=dead|editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt|publisher=[[NASA]]}}</ref> Likely because of a failure by the crew to activate a certain switch in the LM before sealing it off, it tumbled after separation. NASA could not control it, and it did not execute the rocket burn necessary for the craft's intentional de-orbit. The ascent stage eventually crashed into the lunar surface nearly a year after the mission. The crew's next task, after jettisoning the Lunar Module ascent stage, was to release a subsatellite into lunar orbit from the CSM's scientific instrument bay. The burn to alter the CSM's orbit to that desired for the subsatellite had been cancelled; as a result, the subsatellite lasted just over a month in orbit, far less than its anticipated one year. Just under five hours after the subsatellite release, on the CSM's 65th orbit around the Moon, its service propulsion system main engine was reignited to propel the craft on a trajectory that would return it to Earth. The SPS engine performed the burn flawlessly despite the malfunction that had delayed their landing several days previously.<ref name="fullsummary" /><ref name=lmjett/>

During the return to Earth, Mattingly performed an 83-minute EVA to retrieve film cassettes from the cameras in the SIM bay, with assistance from Duke who remained at the command module's hatch.<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=November 6, 2019 |archive-date=February 20, 2022 |archive-url=https://web.archive.org/web/20220220193231/https://www.drewexmachina.com/2017/12/17/a-history-of-deep-space-evas/ |url-status=live }}</ref> At approximately {{convert|173,000|nmi|mi km}} from Earth, it was the second "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. During the EVA, Mattingly set up a biological experiment, the Microbial Ecology Evaluation Device (MEED),<ref name="mattinglyafj">{{cite web|url=https://history.nasa.gov/afj/ap16fj/27_Day10_Pt2.html|title=Apollo 16, Day 10 Part 2 – EVA and Housekeeping|work=Apollo 16 Flight Journal|editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt|publisher=[[NASA]]|access-date=November 6, 2019|archive-date=December 31, 2020|archive-url=https://web.archive.org/web/20201231213255/https://history.nasa.gov/afj/ap16fj/27_Day10_Pt2.html|url-status=live}}</ref> an experiment unique to Apollo 16, to evaluate the response of microbes to the space environment.<ref name=meed>{{cite web|title=Microbial Ecology Evaluation Device (MEED)|url=http://lsda.jsc.nasa.gov/scripts/photoGallery/detail_result.aspx?image_id=2377|work=Life Sciences Data Archive|publisher=[[NASA]]|url-status=dead|archive-url=https://web.archive.org/web/20140407090048/http://lsda.jsc.nasa.gov/scripts/photoGallery/detail_result.aspx?image_id=2377|archive-date=April 7, 2014}}</ref> The crew carried out various housekeeping and maintenance tasks aboard the spacecraft and ate a meal before concluding the day.<ref name="mattinglyafj" />

The penultimate day of the flight was largely spent performing experiments, aside from a twenty-minute press conference during the second half of the day. During the press conference, the astronauts answered questions pertaining to several technical and non-technical aspects of the mission prepared and listed by priority at the [[Lyndon B. Johnson Space Center|Manned Spacecraft Center]] in Houston by journalists covering the flight. In addition to numerous housekeeping tasks, the astronauts prepared the spacecraft for its [[atmospheric entry|atmospheric reentry]] the next day. At the end of the crew's final full day in space, the spacecraft was approximately {{convert|77000|nmi|km|sp=us|order=flip}} from Earth and closing at a rate of about {{convert|7000|ft/s|km/s|sp=us|order=flip}}.<ref>{{cite web|title=Apollo 16: Day 11 Part One: Geology, Experiments and Guidance Fault Investigation|url=https://history.nasa.gov/ap16fj/28_Day11_Pt1.htm|work=Apollo 16 Flight Journal|archive-url=https://web.archive.org/web/20111021155831/http://history.nasa.gov/ap16fj/28_Day11_Pt1.htm|archive-date=October 21, 2011|date=May 15, 2008|url-status=dead|editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt|publisher=[[NASA]]}}</ref><ref>{{cite web|title=Apollo 16: Day 11 Part Two: Press Conference, Experiments and House-Keeping|url=https://history.nasa.gov/ap16fj/29_Day11_Pt2.htm|work=Apollo 16 Flight Journal|archive-url=https://web.archive.org/web/20111021160421/http://history.nasa.gov/ap16fj/29_Day11_Pt2.htm|archive-date=October 21, 2011|date=May 11, 2008|url-status=dead|editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt|publisher=[[NASA]]}}</ref>

When the wake-up call was issued to the crew for their final day in space by CAPCOM England, the CSM was about {{convert|45000|nmi|km}} from Earth, traveling just over {{convert|9000|ft/s|km/s|abbr=on|order=flip}}. Just over three hours before [[splashdown (spacecraft landing)|splashdown]] in the Pacific Ocean, the crew performed a final course correction burn, using the spacecraft's thrusters to change their velocity by {{convert|1.4|ft/s|m/s|abbr=on|order=flip}}. Approximately ten minutes before reentry into Earth's atmosphere, the cone-shaped command module containing the three crewmembers separated from the service module, which would burn up during reentry. At 265 hours and 37 minutes into the mission, at a velocity of about {{convert|36000|ft/s|km/s|abbr=on|order=flip}}, Apollo 16 began atmospheric reentry. At its maximum, the temperature of the heat shield was between {{convert|4000|and|4500|F|C|order=flip}}. After parachute deployment and less than 14 minutes after reentry began, the command module splashed down in the Pacific Ocean {{convert|189|nmi|km|sp=us|order=flip}} southeast of the island of [[Kiritimati]] 265 hours, 51 minutes, 5{{nbsp}}seconds after liftoff.<ref name="timeline" /> The spacecraft and its crew was retrieved by the aircraft carrier {{USS|Ticonderoga|CV-14|6}}. The astronauts were safely aboard the ''Ticonderoga'' 37 minutes after splashdown.<ref name="fullsummary" /><ref>{{cite web|title=Apollo 16: Day 12 – Entry and Splashdown|url= https://history.nasa.gov/afj/ap16fj/30_Day12.html#265_22_32 |work=Apollo 16 Flight Journal|archive-url= https://web.archive.org/web/20201128050530/https://history.nasa.gov/afj/ap16fj/30_Day12.html | archive-date = November 28, 2020 | url-status = live | date = Feb 11, 2020 |editor-first=David|editor-last=Woods|editor2-first=Tim|editor2-last=Brandt|publisher=[[NASA]]}}</ref>