Editing Apollo program (section)

==Samples returned==
{{main|Moon rock}}
{{multiple image
| align             = right
| total_width       = 350
| image1            = Apollo 15 Genesis Rock.jpg
| caption1          = The most famous of the Moon rocks recovered, the [[Genesis Rock]], returned from Apollo&nbsp;15.
| image2            = Lunar_Sample_61016_-_Big_Muley.jpg
| caption2          = Apollo 16's sample 61016, better known as Big Muley, is the largest sample collected during the Apollo program
}}

The Apollo program returned over {{convert|382|kg|lb|abbr=on}} of lunar rocks and [[lunar soil|soil]] to the [[Lunar Receiving Laboratory]] in Houston.<ref>{{cite web |url=https://curator.jsc.nasa.gov/lunar/lun-fac.cfm |title=NASA Lunar Sample Laboatory Facility |date=September 1, 2016 |website=NASA Curation Lunar |publisher=NASA |access-date=February 15, 2017 |quote=A total of 382 kilograms of lunar material, comprising 2200 individual specimens returned from the Moon{{nbsp}}...}}</ref><ref name="Orloff-EVA"/><ref>{{cite book|last1=Chaikin|first1=Andrew|title=A Man On the Moon: The Voyages of the Apollo Astronauts|year=2007|publisher=Penguin Books|location=New York|pages=611–613|edition=Third}}</ref> Today, 75% of the samples are stored at the [[Lunar Sample Laboratory Facility]] built in 1979.<ref>{{cite web|title=Rock Solid: JSC's Lunar Sample Lab Turns 30|url=http://www.nasa.gov/mission_pages/apollo/40th/jsc_lunar_sample_lab_30.html|work= 40th Anniversary of Apollo Program|publisher=NASA|access-date=June 29, 2012|author=Kristen Erickson|editor=Amiko Kauderer|date=July 16, 2009}}</ref>

The rocks collected from the Moon are extremely old compared to rocks found on Earth, as measured by [[radiometric dating]] techniques. They range in age from about 3.2&nbsp;billion years for the [[basalt]]ic samples derived from the [[lunar mare|lunar maria]], to about 4.6&nbsp;billion years for samples derived from the [[Lunar highlands|highlands]] crust.<ref>[[#Papike et al.|Papike et al. 1998]], pp. 5-001–5-234</ref> As such, they represent samples from a very early period in the development of the [[Solar System]], that are largely absent on Earth. One important rock found during the Apollo Program is dubbed the [[Genesis Rock]], retrieved by astronauts David Scott and James Irwin during the Apollo 15 mission.{{sfn|Harland|2008|pp=132–133}} This [[anorthosite]] rock is composed almost exclusively of the calcium-rich feldspar mineral [[anorthite]], and is believed to be representative of the highland crust.{{sfn|Harland|2008|p=171}} A geochemical component called [[KREEP]] was discovered by Apollo 12, which has no known terrestrial counterpart.{{sfn|Harland|2008|pp=49–50}} KREEP and the anorthositic samples have been used to infer that the outer portion of the Moon was once completely molten (see [[lunar magma ocean]]).{{sfn|Harland|2008|pp=323–327}}

Almost all the rocks show evidence of impact process effects. Many samples appear to be pitted with [[micrometeoroid]] impact craters, which is never seen on Earth rocks, due to the thick atmosphere. Many show signs of being subjected to high-pressure shock waves that are generated during impact events. Some of the returned samples are of ''impact melt'' (materials melted near an impact crater.) All samples returned from the Moon are highly [[breccia]]ted as a result of being subjected to multiple impact events.{{sfn|Harland|2008|pp=330–332}}

From analyses of the composition of the returned lunar samples, it is now believed that the Moon was [[Giant-impact hypothesis|created through the impact]] of a large astronomical body with Earth.<ref>[[#Burrows|Burrows 1999]], p. 431</ref>