Editing Apollo 17 (section)

===Lunar surface science===

==== ALSEP ====
The [[Apollo Lunar Surface Experiments Package]] was a suite of nuclear-powered experiments, flown on each landing mission after Apollo 11. This equipment was to be emplaced by the astronauts to continue functioning after the astronauts returned to Earth.{{sfn|Orloff & Harland 2006|pp=601–602}} For Apollo 17, the ALSEP experiments were a [[Heat Flow Experiment]] (HFE), to measure the rate of heat flow from the interior of the Moon, a [[Lunar Surface Gravimeter]] (LSG), to measure alterations in the lunar gravity field at the site,{{sfn|Orloff 2004|loc=Statistical Tables: Lunar Surface Experiments}} a [[Lunar Atmospheric Composition Experiment]] (LACE), to investigate what the lunar atmosphere is made up of,<ref name="lace">{{cite web |title=Science Experiments – Lunar Atmospheric Composition |url=https://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/experiments/lace/#:~:text=The%20Lunar%20Atmospheric%20Composition%20Experiment,by%20the%20Cold%20Cathode%20Gauge. |publisher=Lunar and Planetary Institute |access-date=February 8, 2022 |archive-date=July 9, 2021 |archive-url=https://web.archive.org/web/20210709143320/https://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/experiments/lace/#:~:text=The%20Lunar%20Atmospheric%20Composition%20Experiment,by%20the%20Cold%20Cathode%20Gauge. |url-status=live }}</ref> a [[Lunar Seismic Profiling Experiment]] (LSPE), to detect nearby seismic activity, and a [[Lunar Ejecta and Meteorites Experiment]] (LEME), to measure the velocity and energy of dust particles.{{sfn|Orloff 2004|loc=Statistical Tables: Lunar Surface Experiments}} Of these, only the HFE had been flown before; the others were new.{{sfn|Orloff & Harland 2006|pp=601–602}}

The HFE had been flown on the aborted Apollo 13 mission, as well as on Apollo 15 and 16, but placed successfully only on Apollo 15, and unexpected results from that device made scientists anxious for a second successful emplacement. It was successfully deployed on Apollo 17.{{sfn|Chaikin 1995|pp=467–469, 478, 513}} The lunar gravimeter was intended to detect wavers in gravity, which would provide support for [[Albert Einstein]]'s [[general theory of relativity]];<ref>{{cite news |last1=Lunsford |first1=Christine |title=Apollo 17: NASA's Last Apollo Moon Landing Mission in Pictures |url=https://www.space.com/39006-apollo-17-moon-landing-mission-photos/2.html |access-date=February 8, 2022 |publisher=Space.com |date=December 7, 2017 |archive-date=February 8, 2022 |archive-url=https://web.archive.org/web/20220208025314/https://www.space.com/39006-apollo-17-moon-landing-mission-photos/2.html |url-status=live }}</ref> it ultimately failed to function as intended.<ref name="alsjtge"/> The LACE was a surface-deployed module that used a [[mass spectrometer]] to analyze the Moon's atmosphere.<ref>{{cite report |last1=Stern |first1=S. Alan |title=The Lunar Atmosphere: History, Status, Current Problems, and Context |year=1999 |publisher=Southwest Research Institute |citeseerx=10.1.1.21.9994 }}</ref> On previous missions, the [[Cold Cathode Gauge Experiment|Code Cathode Gauge]] experiment had measured the quantity of atmospheric particles, but the LACE determined which gases were present: principally neon, helium and hydrogen.<ref name="lace"/> The LSPE was a seismic-detecting device that used [[geophone]]s, which would detect explosives to be set off by ground command once the astronauts left the Moon.{{sfn|Orloff 2004|loc=Statistical Tables: Lunar Surface Experiments}} When operating, it could only send useful data to Earth in high bit rate, meaning that no other ALSEP experiment could send data then, and limiting its operating time. It was turned on to detect the liftoff of the ascent stage, as well as use of the explosives packages, and the ascent stage's impact, and thereafter about once a week, as well as for some 100 hour periods.<ref>{{cite web |title=Lunar Seismic Profiling Experiment |url=https://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/experiments/lspe/Apollo-17-active-seismic-NSSDCA.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/experiments/lspe/Apollo-17-active-seismic-NSSDCA.pdf |archive-date=2022-10-09 |url-status=live|publisher=Lunar and Planetary Institute}}</ref> The LEME had a set of detectors to measure the characteristics of the dust particles it sought.{{sfn|Orloff 2004|loc=Statistical Tables: Lunar Surface Experiments}} It was hoped that the LEME would detect dust impacting the Moon from elsewhere, such as from comets or interstellar space, but analysis showed that it primarily detected dust moving at slow speeds across the lunar surface.<ref name="leme">{{cite web |title=Science Experiments – Lunar Ejecta and Meteorite |url=https://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/experiments/lem/ |publisher=Lunar and Planetary Institute |access-date=February 12, 2022 |archive-date=January 20, 2022 |archive-url=https://web.archive.org/web/20220120031105/https://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/experiments/lem/ |url-status=live }}</ref>

All powered ALSEP experiments that remained active were deactivated on September 30, 1977,{{sfn|Orloff & Harland 2006|pp=601–602}} principally because of budgetary constraints.<ref name="astro">{{cite news|newspaper=[[Astronomy (magazine)|Astronomy]]|access-date=February 1, 2021|title=What did the Apollo astronauts leave behind?|date=June 21, 2019|last=Talcott|first=Richard|url=https://astronomy.com/news/2019/06/what-did-the-apollo-astronauts-leave-behind|archive-date=February 1, 2022|archive-url=https://web.archive.org/web/20220201050005/https://astronomy.com/news/2019/06/what-did-the-apollo-astronauts-leave-behind|url-status=live}}</ref>

==== Other lunar-surface science ====
[[File:Apollo 17 rover at final resting site.jpg|thumb|Apollo 17's [[Lunar Roving Vehicle]]. The Surface Electrical Properties (SEP) experiment receiver is the antenna on the right-rear of the vehicle|alt=Black and white photo of a lunar rover with a lunar landing module in the background.]]Like Apollo 15 and 16, Apollo 17 carried a Lunar Roving Vehicle. In addition to being used by the astronauts for transport from station to station on the mission's three moonwalks, the LRV was used to transport the astronauts' tools, communications equipment, and the lunar samples they gathered.<ref name="lunarrover">{{cite web |title=Lunar Roving Vehicle (LRV) |url=https://airandspace.si.edu/explore-and-learn/topics/apollo/apollo-program/spacecraft/lrv.cfm |website=The Apollo Program |publisher=National Air and Space Museum |access-date=February 8, 2022 |archive-date=February 8, 2022 |archive-url=https://web.archive.org/web/20220208032714/https://airandspace.si.edu/explore-and-learn/topics/apollo/apollo-program/spacecraft/lrv.cfm |url-status=dead }}</ref> The Apollo 17 LRV was also used to carry some of the scientific instruments, such as the [[Lunar Traverse Gravimeter|Traverse Gravimeter Experiment (TGE)]] and Surface Electrical Properties (SEP) experiment.<ref name="alsjtge" /><ref name="sep">{{cite web|title=Science Experiments – Surface Electrical Properties|url=http://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/experiments/sep/|work=Apollo 17 Mission|publisher=Lunar and Planetary Institute|access-date=February 7, 2022|archive-date=October 3, 2011|archive-url=https://web.archive.org/web/20111003195214/http://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/experiments/sep/|url-status=live}}</ref> The Apollo 17 LRV traveled a cumulative distance of approximately {{convert|35.7|km|mi nmi|abbr=on}} in a total drive time of about four hours and twenty-six minutes; the greatest distance Cernan and Schmitt traveled from the lunar module was about {{convert|7.6|km|mi nmi|abbr=on}}.{{sfn|Orloff 2004|loc=Statistical Tables: Extravehicular Activity}}

This was the only mission to carry the TGE, which was built by [[Draper Laboratory]] at the [[Massachusetts Institute of Technology]]. As gravimeters had been useful in studying the Earth's internal structure, the objective of this experiment was to do the same on the Moon. The gravimeter was used to obtain relative gravity measurements at the landing site in the immediate vicinity of the lunar module, as well as various locations on the mission's traverse routes. Scientists would then use this data to help determine the geological substructure of the landing site and the surrounding vicinity. Measurements were taken while the TGE was mounted on the LRV, and also while the device was placed on the lunar surface. A total of 26 measurements were taken with the TGE during the mission's three moonwalks, with productive results.<ref name="alsjtge">{{cite web|url=http://www.hq.nasa.gov/alsj/a17/a17-TGE.html|title=Apollo 17 Traverse Gravimeter Experiment|publisher=NASA|editor-first=Eric M.|editor-last=Jones|editor2-first=Ken|editor2-last=Glover|work=Apollo 17 Lunar Surface Journal|access-date=November 29, 2021|archive-date=September 7, 2011|archive-url=https://web.archive.org/web/20110907121516/http://www.hq.nasa.gov/alsj/a17/a17-TGE.html|url-status=live}}</ref>

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

A {{convert|2.4|meter|feet|abbr=on}} long, {{convert|2|cm|inch|abbr=on}} diameter{{sfn|Apollo 17 Press Kit|p=46}} device, the Lunar Neutron Probe was inserted into one of the holes drilled into the surface to collect core samples. It was designed to measure the quantity of neutrons which penetrated to the detectors it bore along its length. This was intended to measure the rate of the "gardening" process on the lunar surface, whereby the regolith on the surface is slowly mixed or buried due to micrometeorites and other events. Placed during the first EVA, it was retrieved during the third and final EVA. The astronauts brought it with them back to Earth, and the measurements from it were compared with the evidence of neutron flux in the core that had been removed from the hole it had been placed in. Results from the probe and from the cores were instrumental in current theories that the top centimeter of lunar regolith turns over every million years, whereas "gardening" to a depth of one meter takes about a billion years.<ref name ="probe">{{cite web|publisher=[[Lunar and Planetary Institute]]|work=Apollo 17 Mission|title=Science Experiments – Lunar Neutron Probe|date=2019|access-date=February 12, 2022|url=https://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/experiments/lnp/|archive-date=September 8, 2021|archive-url=https://web.archive.org/web/20210908125848/https://www.lpi.usra.edu/lunar/missions/apollo/apollo_17/experiments/lnp/|url-status=live}}</ref>