Editing Moon (section)

=== Presence of water ===
{{Main|2 = Lunar water}}
Liquid water cannot persist on the lunar surface. When exposed to solar radiation, water quickly decomposes through a process known as [[photodissociation]] and is lost to space. However, since the 1960s, scientists have hypothesized that water ice may be deposited by impacting [[comets]] or possibly produced by the reaction of oxygen-rich lunar rocks, and hydrogen from [[solar wind]], leaving traces of water which could possibly persist in cold, permanently shadowed craters at either pole on the Moon.<ref name="Margot1999" /><ref>
 {{cite journal |first=William R. |last=Ward |title=Past Orientation of the Lunar Spin Axis |journal=[[Science (journal)|Science]] |date=August 1, 1975 |volume=189 |issue=4200 |pages=377–379 |doi=10.1126/science.189.4200.377 |pmid=17840827 |bibcode=1975Sci...189..377W |s2cid=21185695}}</ref> Computer simulations suggest that up to {{Convert |14000 |km2 |abbr=on}} of the surface may be in permanent shadow.<ref name="M03" /> The presence of usable quantities of water on the Moon is an important factor in rendering [[Colonization of the Moon|lunar habitation]] as a cost-effective plan; the alternative of transporting water from Earth would be prohibitively expensive.<ref name="seedhouse2009" />

In years since, signatures of water have been found to exist on the lunar surface.<ref name="moonwater_18032010" /> In 1994, the [[Clementine mission#Bistatic Radar Experiment|bistatic radar experiment]] located on the ''[[Clementine (spacecraft)|Clementine]]'' spacecraft, indicated the existence of small, frozen pockets of water close to the surface. However, later radar observations by [[Arecibo Telescope|Arecibo]], suggest these findings may rather be rocks ejected from young impact craters.<ref>{{cite web |last=Spudis |first=P. |title=Ice on the Moon |url=http://www.thespacereview.com/article/740/1 |publisher=[[The Space Review]] |date=November 6, 2006 |access-date=April 12, 2007 |url-status=dead |archive-url=https://web.archive.org/web/20070222083000/http://www.thespacereview.com/article/740/1 |archive-date=February 22, 2007}}</ref> In 1998, the [[Lunar Prospector#Neutron Spectrometer (NS)|neutron spectrometer]] on the ''Lunar Prospector'' spacecraft showed that high concentrations of hydrogen are present in the first meter of depth in the regolith near the polar regions.<ref name="Feldman1998" /> Volcanic lava beads, brought back to Earth aboard Apollo 15, showed small amounts of water in their interior.<ref name="Saal2008" />

[[File:Chandrayaan1 Spacecraft Discovery Moon Water.jpg|thumb|In 2008, NASA's Moon Mineralogy Mapper equipment on [[India]]'s ''[[Chandrayaan-1]]'' discovered, for the first time, water-rich minerals (shown in blue around a small crater from which they were ejected).|300x300px]]

The 2008 ''[[Chandrayaan-1]]'' spacecraft has since confirmed the existence of surface water ice, using the on-board [[Moon Mineralogy Mapper]]. The spectrometer observed absorption lines common to [[hydroxyl]], in reflected sunlight, providing evidence of large quantities of water ice, on the lunar surface. The spacecraft showed that concentrations may possibly be as high as 1,000&nbsp;[[parts per million|ppm]].<ref name="Pieters2009" /> Using the mapper's reflectance spectra, indirect lighting of areas in shadow confirmed water ice within 20° latitude of both poles in 2018.<ref>{{cite journal |title=Direct evidence of surface exposed water ice in the lunar polar regions |first1=Shuai |last1=Li |first2=Paul G. |last2=Lucey |first3=Ralph E. |last3=Milliken |first4=Paul O. |last4=Hayne |first5=Elizabeth |last5=Fisher |first6=Jean-Pierre |last6=Williams |first7=Dana M. |last7=Hurley |first8=Richard C. |last8=Elphic |journal=Proceedings of the National Academy of Sciences |volume=115 |issue=36 |pages=8907–8912 |date=August 2018 |doi=10.1073/pnas.1802345115 |pmid=30126996 |pmc=6130389 |bibcode=2018PNAS..115.8907L |doi-access=free}}</ref> In 2009, ''[[LCROSS]]'' sent a {{Convert|2300 |kg |abbr=on}} impactor into a [[Permanently shadowed crater|permanently shadowed]] polar crater, and detected at least {{Convert |100 |kg |abbr=on}} of water in a plume of ejected material.<ref name="Planetary" /><ref name="Colaprete" /> Another examination of the LCROSS data showed the amount of detected water to be closer to {{Convert |155 |± |12 |kg |abbr=on}}.<!--, or 5.6% (±2.9%) by mass.--This seems too technical for this overview--><ref name="Colaprete2010" />

In May 2011, 615–1410 ppm water in [[melt inclusions]] in lunar sample 74220 was reported,<ref name="hauri" /> the famous high-titanium "orange glass soil" of volcanic origin collected during the [[Apollo 17]] mission in 1972. The inclusions were formed during explosive eruptions on the Moon approximately 3.7 billion years ago. This concentration is comparable with that of magma in Earth's [[upper mantle]]. Although of considerable selenological interest, this insight does not mean that water is easily available since the sample originated many kilometers below the surface, and the inclusions are so difficult to access that it took 39 years to find them with a state-of-the-art ion microprobe instrument.

Analysis of the findings of the Moon Mineralogy Mapper (M3) revealed in August 2018 for the first time "definitive evidence" for water-ice on the lunar surface.<ref name=":1">{{Cite news |url=https://www.bbc.co.uk/news/science-environment-45251370 |title=Water ice 'detected on Moon's surface' |last=Rincon |first=Paul |date=August 21, 2018 |work=BBC News |access-date=August 21, 2018 |archive-date=August 21, 2018 |archive-url=https://web.archive.org/web/20180821151638/https://www.bbc.co.uk/news/science-environment-45251370 |url-status=live}}</ref><ref>{{Cite news |url=https://www.scientificamerican.com/article/beyond-the-shadow-of-a-doubt-water-ice-exists-on-the-moon/ |title=Beyond the Shadow of a Doubt, Water Ice Exists on the Moon |last=David |first=Leonard |work=Scientific American |access-date=August 21, 2018 |archive-date=August 21, 2018 |archive-url=https://web.archive.org/web/20180821125629/https://www.scientificamerican.com/article/beyond-the-shadow-of-a-doubt-water-ice-exists-on-the-moon/ |url-status=live}}</ref> The data revealed the distinct reflective signatures of water-ice, as opposed to dust and other reflective substances.<ref name=":2">{{Cite news |url=https://www.space.com/41554-water-ice-moon-surface-confirmed.html |title=Water Ice Confirmed on the Surface of the Moon for the 1st Time! |work=Space.com |access-date=August 21, 2018 |archive-date=August 21, 2018 |archive-url=https://web.archive.org/web/20180821134450/https://www.space.com/41554-water-ice-moon-surface-confirmed.html |url-status=live}}</ref> The ice deposits were found on the North and South poles, although it is more abundant in the South, where water is trapped in permanently shadowed craters and crevices, allowing it to persist as ice on the surface since they are shielded from the sun.<ref name=":1"/><ref name=":2"/>

In October 2020, astronomers reported detecting [[Water|molecular water]] on the sunlit surface of the Moon by several independent spacecraft, including the [[Stratospheric Observatory for Infrared Astronomy]] (SOFIA).<ref name="NA-20201026">{{cite journal |author=Honniball, C.I. |display-authors=et al. |title=Molecular water detected on the sunlit Moon by SOFIA |url=https://www.nature.com/articles/s41550-020-01222-x |date=October 26, 2020 |journal=[[Nature Astronomy]] |volume=5 |issue=2 |pages=121–127 |doi=10.1038/s41550-020-01222-x |bibcode=2021NatAs...5..121H |s2cid=228954129 |access-date=October 26, 2020 |archive-date=October 27, 2020 |archive-url=https://web.archive.org/web/20201027143615/https://www.nature.com/articles/s41550-020-01222-x |url-status=live}}</ref><ref name="NA-20201026poh">{{cite journal |author=Hayne, P.O. |display-authors=et al. |title=Micro cold traps on the Moon |url=https://www.nature.com/articles/s41550-020-1198-9 |date=October 26, 2020 |journal=[[Nature Astronomy]] |volume=5 |issue=2 |pages=169–175 |doi=10.1038/s41550-020-1198-9 |arxiv=2005.05369 |bibcode=2021NatAs...5..169H |s2cid=218595642 |access-date=October 26, 2020 |archive-date=October 27, 2020 |archive-url=https://web.archive.org/web/20201027143618/https://www.nature.com/articles/s41550-020-1198-9 |url-status=live}}</ref><ref name="WP-20201026">{{cite news |last1=Guarino |first1=Ben |last2=Achenbach |first2=Joel |title=Pair of studies confirm there is water on the moon – New research confirms what scientists had theorized for years — the moon is wet. |url=https://www.washingtonpost.com/science/2020/10/26/water-on-the-moon/ |date=October 26, 2020 |newspaper=[[The Washington Post]] |access-date=October 26, 2020 |archive-date=October 26, 2020 |archive-url=https://web.archive.org/web/20201026184808/https://www.washingtonpost.com/science/2020/10/26/water-on-the-moon/ |url-status=live}}</ref><ref name="NYT-20201026">{{cite news |last=Chang |first=Kenneth |title=There's Water and Ice on the Moon, and in More Places Than NASA Once Thought – Future astronauts seeking water on the moon may not need to go into the most treacherous craters in its polar regions to find it. |url=https://www.nytimes.com/2020/10/26/science/moon-ice-water.html |date=October 26, 2020 |work=[[The New York Times]] |access-date=October 26, 2020 |archive-date=October 26, 2020 |archive-url=https://web.archive.org/web/20201026170716/https://www.nytimes.com/2020/10/26/science/moon-ice-water.html |url-status=live}}</ref>