Editing Apollo 17 (section)

====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>