Editing Apollo 16 (section)

==Planning and training==

===Landing site selection===
Apollo 16 was the second of Apollo's [[List of Apollo missions#Alphabetical mission types|J missions]], featuring the use of the [[Lunar Roving Vehicle]], increased scientific capability, and three-day lunar surface stays.<ref name=astronautix>{{cite web|last=Wade|first=Mark|title=Apollo 16|url=http://www.astronautix.com/flights/apollo16.htm|publisher=[[Encyclopedia Astronautica]]|url-status=dead|archive-url=https://web.archive.org/web/20111111125604/http://www.astronautix.com/flights/apollo16.htm|archive-date=November 11, 2011}}</ref> As Apollo 16 was the penultimate mission in the Apollo program and there was no major new hardware or procedures to test on the lunar surface, the last two missions (the other being [[Apollo 17]]) presented opportunities for astronauts to clear up some of the uncertainties in understanding the Moon's characteristics. Scientists sought information on the Moon's early history, which might be obtained from its ancient surface features, the [[Geology of the Moon#Highlands|lunar highlands]]. Previous Apollo expeditions, including Apollo 14 and [[Apollo 15]], had obtained samples of pre-[[Lunar mare|mare]] lunar material, likely thrown from the highlands by [[meteorite]] impacts. These were dated from before [[lava]] began to upwell from the [[Internal structure of the Moon|Moon's interior]] and flood the low areas and basins. Nevertheless, no Apollo mission had actually visited the lunar highlands.<ref name=overview>{{cite web|title=Descartes Surprise|date=September 14, 2006|url=http://www.hq.nasa.gov/alsj/a16/a16.summary.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/20201231213226/https://www.hq.nasa.gov/alsj/a16/a16.summary.html|url-status=live}}</ref>

Apollo 14 had visited and sampled a ridge of material ejected by the impact that created the [[Mare Imbrium|Mare Imbrium impact basin]]. Likewise, Apollo 15 had also sampled material in the region of Imbrium, visiting the basin's edge. Because the Apollo 14 and Apollo 15 landing sites were closely associated with the Imbrium basin, there was still the chance that different geologic processes were prevalent in areas of the lunar highlands far from Mare Imbrium.<ref name=overview/> Scientist Dan Milton, studying photographs of the highlands from [[Lunar Orbiter]] photographs, saw an area in the Descartes region of the Moon with unusually high albedo that he theorized might be due to [[volcanic rock]]; his theory quickly gained wide support.{{sfn|Wilhelms 1993|p=284}} Several members of the scientific community noted that the central lunar highlands resembled regions on Earth that were created by volcanism processes and hypothesized the same might be true on the Moon. They hoped scientific output from the Apollo 16 mission would provide an answer.<ref name=overview/> Some scientists advocated for a landing near the large crater, [[Tycho (lunar crater)|Tycho]], but its distance from the lunar equator and the fact that the Lunar Module would have to approach over very rough terrain ruled it out.{{sfn|Chaikin 1995|pp=454–455}}

[[File:Apollo 16 landing site AS16-M-0440.jpg|thumb|left|300px|Location of the Apollo 16 landing site]]

The Ad Hoc Apollo Site Evaluation Committee met in April and May 1971 to decide the Apollo 16 and 17 landing sites; it was chaired by [[Noel Hinners]] of [[Bellcomm]]. There was consensus the final landing sites should be in the lunar highlands, and among the sites considered for Apollo 16 were the [[Descartes Highlands]] region west of [[Mare Nectaris]] and the crater [[Alphonsus (crater)|Alphonsus]].{{sfn|Wilhelms 1993|p=286}} The considerable distance between the Descartes site and previous Apollo landing sites would also be beneficial for the network of [[seismometer]]s, deployed on each landing mission beginning with Apollo 12.<ref name=lpi>{{cite web|title=Landing Site Overview|url=http://www.lpi.usra.edu/lunar/missions/apollo/apollo_16/landing_site/|work=Apollo 16 Mission|publisher=[[Lunar and Planetary Institute]]|access-date=September 23, 2021|archive-date=November 7, 2012|archive-url=https://web.archive.org/web/20121107170544/http://www.lpi.usra.edu/lunar/missions/apollo/apollo_16/landing_site/|url-status=live}}</ref>

At Alphonsus, three scientific objectives were determined to be of primary interest and paramount importance: the possibility of old, pre-Imbrium impact material from within the crater's wall, the composition of the crater's interior and the possibility of past volcanic activity on the floor of the crater at several smaller "dark halo" craters. Geologists feared, however, that samples obtained from the crater might have been contaminated by the Imbrium impact, thus preventing Apollo 16 from obtaining samples of pre-Imbrium material. There also remained the distinct possibility that this objective would have already been satisfied by the Apollo 14 and Apollo 15 missions, as the Apollo 14 samples had not yet been completely analyzed and samples from Apollo 15 had not yet been obtained.<ref name=lpi/>

On June 3, 1971, the site selection committee decided to target the Apollo 16 mission for the Descartes site.{{sfn|Wilhelms 1993|p=288}} Following the decision, the Alphonsus site was considered the most likely candidate for Apollo 17, but was eventually rejected. With the assistance of orbital photography obtained on the Apollo 14 mission, the Descartes site was determined to be safe enough for a crewed landing. The specific landing site was between two young impact craters, [[North Ray (crater)|North Ray]] and [[South Ray (crater)|South Ray]] craters – {{convert|1000|and|680|m|ft|abbr=on|sp=us}} in diameter, respectively – which provided "natural drill holes" which penetrated through the lunar [[regolith]] at the site, thus leaving exposed [[bedrock]] that could be sampled by the crew.<ref name=lpi/>

After the selection, mission planners made the Descartes and Cayley formations, two geologic units of the lunar highlands, the primary sampling interest of the mission. It was these formations that the scientific community widely suspected were formed by lunar volcanism, but this hypothesis was proven incorrect by the composition of lunar samples from the mission.<ref name=lpi/>

===Training===
[[File:Young and Duke train for Apollo 16.jpg|thumb|right|John Young and Charles Duke training at the [[Rio Grande Gorge]] in [[New Mexico]]]]
In addition to the usual Apollo spacecraft training, Young and Duke, along with backup commander Fred Haise, underwent an extensive [[geology|geological]] training program that included several field trips to introduce them to concepts and techniques they would use in analyzing features and collecting samples on the lunar surface. During these trips, they visited and provided scientific descriptions of geologic features they were likely to encounter.{{sfn|Phinney 2015|pp=125–126}}<ref name=training2>{{cite web|title=Apollo Geology Field Exercises|url=http://next.nasa.gov/alsj/ap-geotrips.html|publisher=[[NASA]]|date=April 29, 2006|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/20111017212419/http://next.nasa.gov/alsj/ap-geotrips.html|archive-date=October 17, 2011}}</ref><ref name=geotrips>{{cite web|title=Apollo Geology Field Exercises|url=http://next.nasa.gov/alsj/ap-geotrips.pdf|publisher=[[NASA]]|url-status=dead|archive-url=https://web.archive.org/web/20111021152443/http://next.nasa.gov/alsj/ap-geotrips.pdf|archive-date=October 21, 2011}}</ref> The backup LMP, Mitchell, was unavailable during the early part of the training, occupied with tasks relating to Apollo 14, but by September 1971 had joined the geology field trips. Before that, Tony England (a member of the support crew and the lunar EVA CAPCOM) or one of the geologist trainers would train alongside Haise on geology field trips.{{sfn|Phinney 2015|p=125}}

Since Descartes was believed to be volcanic, a good deal of this training was geared towards volcanic rocks and features, but field trips were made to sites featuring other sorts of rock. As Young later commented, the non-volcanic training proved more useful, given that Descartes did not prove to be volcanic.{{sfn|Phinney 2015|p=97}} In July 1971, they visited [[Greater Sudbury|Sudbury]], Ontario, Canada, for geology training exercises, the first time U.S. astronauts trained in Canada.<ref name=sudburytraining /> The Apollo 14 landing crew had visited a site in [[West Germany]]; geologist [[Don Wilhelms]] related that unspecified incidents there had caused Slayton to rule out further European training trips.{{sfn|Wilhelms 1993|p=290}} Geologists chose Sudbury because of a {{convert|60|mi|km|abbr=on|order=flip}} wide crater created about 1.8&nbsp;billion years ago by a large meteorite.<ref name=sudburytraining /> The [[Sudbury Basin]] shows evidence of [[shatter cone]] geology, familiarizing the Apollo crew with geologic evidence of a meteorite impact. During the training exercises the astronauts did not wear [[Apollo/Skylab A7L|space suits]], but carried radio equipment to converse with each other and England, practicing procedures they would use on the lunar surface.<ref name=sudburytraining>{{cite news|last=Dickie|first=Allan|title=Astronauts training in Ont.|url=https://news.google.com/newspapers?id=s-9UAAAAIBAJ&pg=1178,849265&dq=apollo+16+training&hl=en|access-date=November 26, 2011|agency=[[The Canadian Press]]|newspaper=[[Leader-Post|The Leader-Post]]|location=Regina, Saskatchewan|date=July 7, 1971|archive-date=February 1, 2022|archive-url=https://web.archive.org/web/20220201050007/https://news.google.com/newspapers?id=s-9UAAAAIBAJ&pg=1178%2C849265&dq=apollo+16+training&hl=en|url-status=live}}</ref> By the end of the training, the field trips had become major exercises, involving up to eight astronauts and dozens of support personnel, attracting coverage from the media. For the exercise at the [[Nevada Test Site]], where the massive craters left by nuclear explosions simulated the large craters to be found on the Moon, all participants had to have security clearance and a listed next-of-kin, and an overflight by CMP Mattingly required special permission.{{sfn|Phinney 2015|p=125}}<ref>{{cite news|access-date=September 20, 2021|publisher=Science and Technology News|title=Apollo astronauts train at the Nevada Test Site|url=https://st.llnl.gov/news/look-back/apollo-astronauts-train-nevada-test-site|archive-date=October 29, 2021|archive-url=https://web.archive.org/web/20211029065341/https://st.llnl.gov/news/look-back/apollo-astronauts-train-nevada-test-site|url-status=live}}</ref>

[[File:Moon Buggy Ap16-KSC-71PC-777.jpg|thumb|upright=1.4|left|Young (right) and Duke training to drive the [[Lunar Roving Vehicle]]]]
In addition to the field geology training, Young and Duke also trained to use their EVA space suits, adapt to the reduced [[Gravitation of the Moon|lunar gravity]], collect samples, and drive the Lunar Roving Vehicle.<ref name=training3 /> The fact that they had been backups for Apollo 13, planned to be a landing mission, meant that they could spend about 40 percent of their time training for their surface operations.<ref name = "overview" /> They also received survival training and prepared for technical aspects of the mission.<ref name=training3>{{cite magazine|last=Mason|first=Betsy|title=The Incredible Things NASA Did to Train Apollo Astronauts|url=https://www.wired.com/wiredscience/2011/07/moon-landing-gallery/?pid=1688&viewall=true|access-date=November 26, 2011|magazine=[[Wired (magazine)|Wired Science]]|publisher=[[Condé Nast Publications]]|date=July 20, 2011|archive-date=September 13, 2011|archive-url=https://web.archive.org/web/20110913083741/http://www.wired.com/wiredscience/2011/07/moon-landing-gallery?pid=1688&viewall=true|url-status=live}}</ref> The astronauts spent much time studying the lunar samples brought back by earlier missions, learning about the instruments to be carried on the mission, and hearing what the principal investigators in charge of those instruments expected to learn from Apollo 16. This training helped Young and Duke, while on the Moon, quickly realize that the expected volcanic rocks were not there, even though the geologists in Mission Control initially did not believe them.{{sfn|Phinney 2015|p=127}}  Much of the training—according to Young, 350 hours—was conducted with the crew wearing space suits, something that Young deemed vital, allowing the astronauts to know the limitations of the equipment in doing their assigned tasks.{{sfn|Phinney 2015|pp=128–129}} Mattingly also received training in recognizing geological features from orbit by flying over the field areas in an airplane, and trained to operate the Scientific Instrument Module from lunar orbit.{{sfn|Phinney 2015|p=16}}