Editing Moon (section)

==Physical characteristics==
The Moon is a very slightly scalene [[ellipsoid]] due to tidal stretching, with its long axis displaced 30° from facing the Earth, due to gravitational anomalies from impact basins. Its shape is more elongated than current tidal forces can account for. This 'fossil bulge' indicates that the Moon solidified when it orbited at half its current distance to the Earth,<!--at ≈32 Earth radii, currently at 60.3--> and that it is now too cold for its shape to restore [[hydrostatic equilibrium]] at its current orbital distance.<ref>{{cite journal |last1=Garrick-Bethell |first1=Ian |last2=Perera |first2=Viranga |last3=Nimmo |first3=Francis |last4=Zuber |first4=Maria T. |year=2014 |title=The tidal-rotational shape of the Moon and evidence for polar wander |url=https://escholarship.org/content/qt0012r6g6/qt0012r6g6.pdf?t=npc7m2 |journal=Nature |volume=512 |issue=7513 |pages=181–184 |doi=10.1038/nature13639 |pmid=25079322 |bibcode=2014Natur.512..181G |s2cid=4452886 |access-date=April 12, 2020 |archive-date=August 4, 2020 |archive-url=https://web.archive.org/web/20200804071339/https://escholarship.org/content/qt0012r6g6/qt0012r6g6.pdf?t=npc7m2 |url-status=live}}</ref>

===Size and mass===
{{Further|List of natural satellites}}
[[File:Moons of solar system v7.jpg|thumb|upright=1.5|Size comparison of the main moons of the Solar System with Earth to scale. Nineteen moons are large enough [[Hydrostatic equilibrium|to be round]], several having [[subsurface ocean]]s and one, Titan, having a considerable atmosphere.]]
The Moon is by size and mass the fifth largest natural satellite of the Solar System, categorizable as one of its [[planetary-mass moon]]s, making it a satellite planet under the [[geophysical definition of planet|geophysical definitions of the term]].<ref name="Metzger2021">{{Citation |last1=Metzger |first1=Philip |author-link1=Philip T. Metzger |last2=Grundy |first2=Will |last3=Sykes |first3=Mark |last4=Stern |first4=Alan |last5=Bell |first5=James |last6=Detelich |first6=Charlene |last7=Runyon |first7=Kirby |last8=Summers |first8=Michael |date=2021 |title=Moons are planets: Scientific usefulness versus cultural teleology in the taxonomy of planetary science |journal=[[Icarus (journal)|Icarus]] |volume=374 |page=114768 |doi=10.1016/j.icarus.2021.114768 |arxiv=2110.15285 |bibcode=2022Icar..37414768M |s2cid=240071005}}</ref> It is smaller than [[Mercury (planet)|Mercury]] and considerably larger than the largest [[dwarf planet]] of the Solar System, [[Pluto]]. The Moon is the largest natural satellite in the Solar System relative to its [[Primary (astronomy)|primary]] planet.{{efn |There is no strong correlation between the sizes of planets and the sizes of their satellites. Larger planets tend to have more satellites, both large and small, than smaller planets.}}{{efn|name=Moon vs. Charon}}<ref>{{cite web |url=http://www.planetary.org/explore/topics/pluto/ |title=Space Topics: Pluto and Charon |publisher=[[The Planetary Society]] |access-date=April 6, 2010 |url-status=dead |archive-url=https://web.archive.org/web/20120218223842/http://www.planetary.org/explore/topics/pluto/ |archive-date=February 18, 2012}}</ref>

The Moon's diameter is about 3,500&nbsp;km, more than one-quarter of Earth's, with the face of the Moon comparable to the width of either [[mainland Australia]],<ref name="Australia">{{cite web |url=https://theconversation.com/how-big-is-the-moon-let-me-compare-118840 |date=July 18, 2019 |access-date=November 15, 2020 |title=How big is the Moon? |first=Jonti |last=Horner |archive-date=November 7, 2020 |archive-url=https://web.archive.org/web/20201107223707/http://theconversation.com/how-big-is-the-moon-let-me-compare-118840 |url-status=live}}</ref> Europe or the [[contiguous United States]].<ref name="Dyches 2021 d923">{{cite news |last=Dyches |first=Preston |title=Five Things to Know about the Moon |work=NASA Solar System Exploration |date=July 28, 2021 |url=https://solarsystem.nasa.gov/news/1946/five-things-to-know-about-the-moon/ |access-date=September 24, 2023 |archive-date=July 18, 2023 |archive-url=https://web.archive.org/web/20230718090707/https://solarsystem.nasa.gov/news/1946/five-things-to-know-about-the-moon/ |url-status=live}}</ref> The whole surface area of the Moon is about 38&nbsp;million square kilometers, comparable to that of the [[Americas]].<ref name="y857">{{cite magazine |last=Parks |first=Jake |title=Everything you need to know about the Moon |magazine=Astronomy |date=2023-09-07 |url=https://www.astronomy.com/observing/everything-you-need-to-know-about-the-moon/ |access-date=2024-09-09}}</ref><ref name="f708">{{cite web |title=Global Island Explorer |publisher=United States Geological Survey |url=https://rmgsc.cr.usgs.gov/gie/gie.shtml |access-date=2024-09-09 }}{{Dead link|date=April 2025 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

The Moon's mass is {{frac|1|81}} of Earth's,<ref name="worldbook" /> being the second densest among the planetary moons, and having the second highest [[surface gravity]], after [[Io (moon)|Io]], at {{val |0.1654 |u=[[G-force|g]]}} and an escape velocity of {{convert|2.38|km/s|km/h mph|comma=gaps|abbr=on}}.

===Structure===
{{Main|Internal structure of the Moon|Geology of the Moon}}
[[File:Return of the moon diagram.svg|thumb|upright=1.5|Moon's internal structure: solid inner core (iron-metallic), molten outer core, hardened mantle and crust. The crust on the Moon's near side permanently facing Earth is thinner, featuring larger areas flooded by material of the once molten mantle forming today's [[lunar mare]].]]
The Moon is a [[planetary differentiation|differentiated]] body that was initially in [[hydrostatic equilibrium]] but has since departed from this condition.<ref>{{cite journal |title=Interpretation of lunar potential fields |first=Stanley Keith |last=Runcorn |date=March 31, 1977 |journal=Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences |doi=10.1098/rsta.1977.0094 |bibcode=1977RSPTA.285..507R |volume=285 |issue=1327 |pages=507–516 |s2cid=124703189}}</ref> It has a [[geochemically]] distinct [[Crust (geology)|crust]], [[Mantle (geology)|mantle]], and [[Planetary core|core]]. The Moon has a solid iron-rich inner core with a radius possibly as small as {{convert|240|km}} and a fluid outer core primarily made of liquid iron with a radius of roughly {{convert|300|km}}. Around the core is a partially molten boundary layer with a radius of about {{convert|500|km}}.<ref>{{cite web |last1=Brown |first1=D. |last2=Anderson |first2=J. |website=NASA |url=http://www.nasa.gov/topics/moonmars/features/lunar_core.html |title=NASA Research Team Reveals Moon Has Earth-Like Core |date=January 6, 2011 |url-status=live |archive-url=https://web.archive.org/web/20120111112210/http://www.nasa.gov/topics/moonmars/features/lunar_core.html |archive-date=January 11, 2012}}</ref><ref name="Weber2011">{{cite journal |last1=Weber |first1=R.C. |last2=Lin |first2=P.-Y. |last3=Garnero |first3=E.J. |last4=Williams |first4=Q. |last5=Lognonne |first5=P. |title=Seismic Detection of the Lunar Core |journal=Science |volume=331 |issue=6015 |date=January 21, 2011 |pages=309–312 |url=http://www.earth.northwestern.edu/people/seth/351/lunarcore.2011.pdf |doi=10.1126/science.1199375 |pmid=21212323 |url-status=dead |archive-url=https://web.archive.org/web/20151015035756/http://www.earth.northwestern.edu/people/seth/351/lunarcore.2011.pdf |archive-date=October 15, 2015 |bibcode=2011Sci...331..309W |s2cid=206530647 |access-date=April 10, 2017}}</ref> This structure is thought to have developed through the [[Fractional crystallization (geology)|fractional crystallization]] of a global magma ocean shortly after the Moon's formation 4.5&nbsp;billion years ago.<ref>{{cite journal |doi=10.1038/ngeo417 |title=Timing of crystallization of the lunar magma ocean constrained by the oldest zircon |date=2009 |last1=Nemchin |first1=A. |last2=Timms |first2=N. |last3=Pidgeon |first3=R. |last4=Geisler |first4=T. |last5=Reddy |first5=S. |last6=Meyer |first6=C. |journal=[[Nature Geoscience]] |volume=2 |issue=2 |pages=133–136 |bibcode=2009NatGe...2..133N |hdl=20.500.11937/44375 |hdl-access=free}}</ref>

Crystallization of this magma ocean would have created a [[mafic]] mantle from the [[Precipitation (chemistry)|precipitation]] and sinking of the minerals [[olivine]], [[clinopyroxene]], and [[orthopyroxene]]; after about three-quarters of the magma ocean had crystallized, lower-density [[plagioclase]] minerals could form and float into a crust atop.<ref name="S06" /> The final liquids to crystallize would have been initially sandwiched between the crust and mantle, with a high abundance of [[Compatibility (geochemistry)|incompatible]] and heat-producing elements.<ref name="W06" /> Consistent with this perspective, geochemical mapping made from orbit suggests a crust of mostly [[anorthosite]].<ref name="L06" /> The [[Moon rock]] samples of the flood lavas that erupted onto the surface from partial melting in the mantle confirm the mafic mantle composition, which is more iron-rich than that of Earth.<ref name="W06" /> The crust is on average about {{convert|50|km}} thick.<ref name="W06" />

The Moon is the second-densest satellite in the Solar System, after [[Io (moon)|Io]].<ref name="Schubert2004" /> However, the inner core of the Moon is small, with a radius of about {{convert|350|km}} or less,<ref name="W06" /> around 20% of the radius of the Moon. Its composition is not well understood but is probably metallic iron alloyed with a small amount of sulfur and nickel. Analyses of the Moon's time-variable rotation suggest that it is at least partly molten.<ref>{{cite journal |last1=Williams |first1=J.G. |last2=Turyshev |first2=S.G. |last3=Boggs |first3=D.H. |last4=Ratcliff |first4=J.T. |title=Lunar laser ranging science: Gravitational physics and lunar interior and geodesy |journal=[[Advances in Space Research]] |date=2006 |volume=37 |issue=1 |pages=67–71 |bibcode=2006AdSpR..37...67W |doi=10.1016/j.asr.2005.05.013 |arxiv=gr-qc/0412049 |s2cid=14801321}}</ref> The pressure at the lunar core is estimated to be {{cvt|5|GPa|atm}}.<ref>{{cite journal |title=The Case Against an Early Lunar Dynamo Powered by Core Convection |last1=Evans |first1=Alexander J. |last2=Tikoo |first2=Sonia M. |first3=Andrews-Hanna |last3=Jeffrey C. |journal=Geophysical Research Letters |date=January 2018 |volume=45 |issue=1 |pages=98–107 |doi=10.1002/2017GL075441 |bibcode=2018GeoRL..45...98E |doi-access=free}}</ref>

=== Gravitational field ===
[[File:Youtubeastronautsonmoonot3.gif|thumb|Astronaut [[John Young (astronaut)|John Young]] jumping on the Moon, illustrating that the [[Gravitational acceleration|gravitational pull]] of the Moon is approximately 1/6 of Earth's. The jumping height is limited by the EVA space suit's weight on the Moon of about {{cvt|13.6|kg|lbs}} and by the suit's pressurization resisting the bending of the suit, as needed for jumping.<ref name="Kluger 2018 z081">{{cite magazine |last=Kluger |first=Jeffrey |title=How Neil Armstrong's Moon Spacesuit Was Preserved for Centuries to Come |magazine=Time |date=October 12, 2018 |url=https://time.com/5422609/armstrong-spacesuit-smithsonian/ |access-date=November 29, 2023 |archive-date=December 3, 2023 |archive-url=https://web.archive.org/web/20231203061321/https://time.com/5422609/armstrong-spacesuit-smithsonian/ |url-status=live}}</ref><ref name="Nast 2013 v237">{{cite magazine |title=How Do You Pick Up Something on the Moon? |magazine=WIRED |date=December 9, 2013 |url=https://www.wired.com/2013/12/how-do-you-pick-up-something-on-the-moon/ |access-date=November 29, 2023 |archive-date=December 3, 2023 |archive-url=https://web.archive.org/web/20231203061321/https://www.wired.com/2013/12/how-do-you-pick-up-something-on-the-moon/ |url-status=live}}</ref>]]

On average the Moon's [[surface gravity]] is {{val|1.62|ul=m/s2}}<ref name="NSSDC" /> ({{val|0.1654|u=[[G-force|g]]}}; {{val|5.318|ul=ft/s2}}), about half of the surface gravity of [[Mars]] and about a sixth of Earth's.

The [[Gravitation of the Moon|Moon's gravitational field]] is not uniform. The details of the gravitational field have been measured through tracking the [[Doppler shift]] of radio signals emitted by orbiting spacecraft. The main lunar gravity features are [[mass concentration (astronomy)|mascons]], large positive gravitational anomalies associated with some of the giant impact basins, partly caused by the dense mare basaltic lava flows that fill those basins.<ref>{{cite journal |last=Muller |first=P. |author2=Sjogren, W. |title=Mascons: lunar mass concentrations |journal=[[Science (journal)|Science]] |volume=161 |pages=680–684 |date=1968 |doi=10.1126/science.161.3842.680 |pmid=17801458 |issue=3842 |bibcode=1968Sci...161..680M |s2cid=40110502}}</ref><ref>{{cite journal |journal=[[Science (journal)|Science]] |author=Richard A. Kerr |title=The Mystery of Our Moon's Gravitational Bumps Solved? |volume=340 |issue=6129 |pages=138–139 |date=April 12, 2013 |doi=10.1126/science.340.6129.138-a |pmid=23580504}}</ref> The anomalies greatly influence the orbit of spacecraft about the Moon. There are some puzzles: lava flows by themselves cannot explain all of the gravitational signature, and some mascons exist that are not linked to mare volcanism.<ref>{{cite journal |last=Konopliv |first=A. |author2=Asmar, S. |author3=Carranza, E. |author4=Sjogren, W. |author5=Yuan, D. |title=Recent gravity models as a result of the Lunar Prospector mission |journal=[[Icarus (journal)|Icarus]] |volume=50 |issue=1 |pages=1–18 |date=2001 |doi=10.1006/icar.2000.6573 |bibcode=2001Icar..150....1K |url=http://techreports.jpl.nasa.gov/2000/00-1301.pdf |url-status=dead |archive-url=https://web.archive.org/web/20041113045200/http://techreports.jpl.nasa.gov/2000/00-1301.pdf |archive-date=November 13, 2004 |citeseerx=10.1.1.18.1930}}</ref>

=== Magnetic field ===
The Moon has [[Magnetic field of the Moon|an external magnetic field]] of less than 0.2 [[Tesla (unit)|nanoteslas]],<ref name="Mighani2020">{{cite journal |last1=Mighani |first1=S. |last2=Wang |first2=H. |last3=Shuster |first3=D.L. |last4=Borlina |first4=C.S. |last5=Nichols |first5=C.I.O. |last6=Weiss |first6=B.P. |title=The end of the lunar dynamo |journal=Science Advances |volume=6 |issue=1 |year=2020 |pages=eaax0883 |doi=10.1126/sciadv.aax0883 |pmid=31911941 |pmc=6938704 |bibcode=2020SciA....6..883M}}</ref> or less than one hundred thousandth [[Earth's magnetic field|that of Earth]]. The Moon does not have a global [[dipolar]] magnetic field and only has crustal magnetization likely acquired early in its history when a dynamo was still operating.<ref name="GB2009" /><ref>{{cite web |url=http://lunar.arc.nasa.gov/results/magelres.htm |publisher=[[Lunar Prospector]] (NASA) |title=Magnetometer / Electron Reflectometer Results |date=2001 |access-date=March 17, 2010 |url-status=dead |archive-url=https://web.archive.org/web/20100527121330/http://lunar.arc.nasa.gov/results/magelres.htm |archive-date=May 27, 2010}}</ref> Early in its history, 4 billion years ago, its magnetic field strength was likely close to that of Earth today.<ref name="Mighani2020" /> This early dynamo field apparently expired by about one billion years ago, after the lunar core had crystallized.<ref name="Mighani2020" /> Theoretically, some of the remnant magnetization may originate from transient magnetic fields generated during large impacts through the expansion of plasma clouds. These clouds are generated during large impacts in an ambient magnetic field. This is supported by the location of the largest crustal magnetizations situated near the [[antipodes]] of the giant impact basins.<ref>{{cite journal |last=Hood |first=L.L. |author2=Huang, Z. |title=Formation of magnetic anomalies antipodal to lunar impact basins: Two-dimensional model calculations |journal=[[Journal of Geophysical Research]] |volume=96 |issue=B6 |pages=9837–9846 |date=1991 |doi=10.1029/91JB00308 |bibcode=1991JGR....96.9837H}}</ref>

=== Atmosphere ===
{{Main|Atmosphere of the Moon}}
[[File:Apollo 17 twilight ray sketch.jpg|thumb|The thin lunar atmosphere is visible on the Moon's surface at [[sunrise]] and [[sunset]] with the [[lunar horizon glow]]<ref name="The Planetary Society 2016">{{cite web |title=Lunar horizon glow from Surveyor 7 |website=The Planetary Society |date=May 6, 2016 |url=https://www.planetary.org/space-images/lunar-horizon-glow-surveyor-7 |access-date=August 8, 2022 |archive-date=August 8, 2022 |archive-url=https://web.archive.org/web/20220808062356/https://www.planetary.org/space-images/lunar-horizon-glow-surveyor-7 |url-status=live}}</ref> and lunar twilight rays, like Earth's [[crepuscular rays]]. This [[Apollo 17]] sketch depicts the glow and rays<ref name="Science Mission Directorate 2013">{{cite web |title=NASA Mission To Study Mysterious Lunar Twilight Rays |website=Science Mission Directorate |date=September 3, 2013 |url=https://science.nasa.gov/science-news/science-at-nasa/2013/03sep_ladee |access-date=August 8, 2022 |archive-date=July 3, 2022 |archive-url=https://web.archive.org/web/20220703030019/https://science.nasa.gov/science-news/science-at-nasa/2013/03sep_ladee/ |url-status=live}}</ref> among the general [[zodiacal light]].<ref name="Colwell Robertson Horányi Wang 2009 pp. 2–9">{{cite journal |last1=Colwell |first1=Joshua E. |last2=Robertson |first2=Scott R. |last3=Horányi |first3=Mihály |last4=Wang |first4=Xu |last5=Poppe |first5=Andrew |last6=Wheeler |first6=Patrick |title=Lunar Dust Levitation |journal=Journal of Aerospace Engineering |volume=22 |issue=1 |date=January 1, 2009 |doi=10.1061/(ASCE)0893-1321(2009)22:1(2) |pages=2–9 |url=https://ascelibrary.org/doi/10.1061/%28ASCE%290893-1321%282009%2922%3A1%282%29 |access-date=August 8, 2022 |archive-date=August 8, 2022 |archive-url=https://web.archive.org/web/20220808202200/https://ascelibrary.org/doi/10.1061/(ASCE)0893-1321(2009)22:1(2) |url-status=live}}</ref><ref name="EarthSky Updates on your cosmos and world 2014">{{cite web |title=The zodiacal light, seen from the moon |website=EarthSky |author=Deborah Byrd |date=April 24, 2014 |url=https://earthsky.org/space/the-zodiacal-light-seen-from-the-moon/ |access-date=August 8, 2022 |archive-date=August 8, 2022 |archive-url=https://web.archive.org/web/20220808062351/https://earthsky.org/space/the-zodiacal-light-seen-from-the-moon/ |url-status=live}}</ref>]]

The Moon has an [[atmosphere]] consisting of only an [[exosphere]],<ref name="l546">{{cite web | last=Barry | first=Caela | title=The Moon's Atmosphere | website=NASA Science | date=2025-01-30 | url=https://science.nasa.gov/moon/lunar-atmosphere/ | access-date=2025-03-07}}</ref> which is so tenuous as to be nearly [[vacuum]], with a total mass of less than {{Convert|10 |t}}.<ref>{{cite book |editor=Richard D. Johnson & Charles Holbrow |last=Globus |first=Ruth |title=Space Settlements: A Design Study |chapter=Chapter 5, Appendix J: Impact Upon Lunar Atmosphere |publisher=NASA |chapter-url=http://settlement.arc.nasa.gov/75SummerStudy/5appendJ.html |date=1977 |access-date=March 17, 2010 |url-status=dead |archive-url=https://web.archive.org/web/20100531205037/http://settlement.arc.nasa.gov/75SummerStudy/5appendJ.html |archive-date=May 31, 2010}}</ref> The surface pressure of this small mass is around 3 × 10<sup>−15</sup>&nbsp;[[Atmosphere (unit)|atm]] (0.3&nbsp;[[nanopascal|nPa]]); it varies with the lunar day. Its sources include [[outgassing]] and [[sputtering]], a product of the bombardment of lunar soil by solar wind ions.<ref name="L06" /><ref>{{cite journal |last=Crotts |first=Arlin P.S. |title=Lunar Outgassing, Transient Phenomena and The Return to The Moon, I: Existing Data |date=2008 |url=http://www.astro.columbia.edu/~arlin/TLP/paper1.pdf |bibcode=2008ApJ...687..692C |volume=687 |issue=1 |pages=692–705 |journal=[[The Astrophysical Journal]] |doi=10.1086/591634 |arxiv=0706.3949 |s2cid=16821394 |url-status=dead |archive-url=https://web.archive.org/web/20090220081142/http://www.astro.columbia.edu/~arlin/TLP/paper1.pdf |archive-date=February 20, 2009 |access-date=September 29, 2009}}</ref> Elements that have been detected include [[sodium]] and [[potassium]], produced by sputtering (also found in the atmospheres of Mercury and [[Io (moon)|Io]]); [[helium-4]] and [[neon]]<ref name="NASA-20150817">{{cite web |last=Steigerwald |first=William |title=NASA's LADEE Spacecraft Finds Neon in Lunar Atmosphere |url=http://www.nasa.gov/content/goddard/ladee-lunar-neon |date=August 17, 2015 |work=NASA |access-date=August 18, 2015 |archive-date=August 19, 2015 |archive-url=https://web.archive.org/web/20150819035151/http://www.nasa.gov/content/goddard/ladee-lunar-neon/ |url-status=live}}</ref> from the solar wind; and [[Argon|argon-40]], [[Radon|radon-222]], and [[polonium-210]], outgassed after their creation by [[radioactive decay]] within the crust and mantle.<ref name="Stern1999" /><ref>{{cite journal |last=Lawson |first=S. |author2=Feldman, W. |author3=Lawrence, D. |author4=Moore, K. |author5=Elphic, R. |author6=Belian, R. |title=Recent outgassing from the lunar surface: the Lunar Prospector alpha particle spectrometer |journal=[[Journal of Geophysical Research]] |volume=110 |issue=E9 |page=1029 |date=2005 |doi=10.1029/2005JE002433 |doi-access=free |bibcode=2005JGRE..110.9009L}}</ref> The absence of such neutral species (atoms or molecules) as [[oxygen]], [[nitrogen]], [[carbon]], [[hydrogen]] and [[magnesium]], which are present in the [[regolith]], is not understood.<ref name="Stern1999" /> Water vapor has been detected by ''[[Chandrayaan-1]]'' and found to vary with latitude, with a maximum at ~60–70&nbsp;degrees; it is possibly generated from the [[sublimation (chemistry)|sublimation]] of water ice in the regolith.<ref name="Sridharan2010" /> These gases either return into the regolith because of the Moon's gravity or are lost to space, either through solar radiation pressure or, if they are ionized, by being swept away by the solar wind's magnetic field.<ref name="Stern1999" />

Studies of Moon magma samples retrieved by the [[Apollo program|Apollo]] missions demonstrate that the Moon had once possessed a relatively thick atmosphere for a period of 70 million years between 3 and 4 billion years ago. This atmosphere, sourced from gases ejected from lunar volcanic eruptions, was twice the thickness of that of present-day [[Mars]]. The ancient lunar atmosphere was eventually stripped away by solar winds and dissipated into space.<ref name="John 2017"/>

A permanent [[Moon dust]] cloud exists around the Moon, generated by small particles from comets. Estimates are 5 tons of comet particles strike the Moon's surface every 24 hours, resulting in the ejection of dust particles. The dust stays above the Moon approximately 10 minutes, taking 5 minutes to rise, and 5 minutes to fall. On average, 120 kilograms of dust are present above the Moon, rising up to 100 kilometers above the surface. Dust counts made by [[LADEE]]'s Lunar Dust EXperiment (LDEX) found particle counts peaked during the [[Geminid]], [[Quadrantid]], [[Taurids|Northern Taurid]], and [[Omicron Centaurids|Omicron Centaurid]] [[meteor shower]]s, when the Earth, and Moon pass through comet debris. The lunar dust cloud is asymmetric, being denser near the boundary between the Moon's dayside and nightside.<ref>{{cite web |title=Lopsided Cloud of Dust Discovered Around the Moon |url=http://news.nationalgeographic.com/2015/06/150617-moon-dust-cloud-comet-space |website=National Geographic News |access-date=June 20, 2015 |first1=Nadia |last1=Drake |author1-link=Nadia Drake |url-status=dead |archive-url=https://web.archive.org/web/20150619052915/http://news.nationalgeographic.com/2015/06/150617-moon-dust-cloud-comet-space/ |archive-date=June 19, 2015 |date=June 17, 2015}}</ref><ref>{{Cite journal |title=A permanent, asymmetric dust cloud around the Moon |journal=[[Nature (journal)|Nature]] |date=June 18, 2015 |pages=324–326 |volume=522 |issue=7556 |doi=10.1038/nature14479 |first1=M. |last1=Horányi |first2=J.R. |last2=Szalay |first3=S. |last3=Kempf |first4=J. |last4=Schmidt |first5=E. |last5=Grün |first6=R. |last6=Srama |first7=Z. |last7=Sternovsky |bibcode=2015Natur.522..324H |pmid=26085272 |s2cid=4453018}}</ref>

===Surface conditions===
[[File:AS17-145-22224.jpg|thumb|[[Gene Cernan]] with [[lunar dust]] stuck on his suit. Lunar dust is highly abrasive and can cause damage to human lungs and nervous and cardiovascular systems.<ref>{{Cite web |last1=James |first1=John |last2=Kahn-Mayberry |first2=Noreen |date=Jan 2009 |title=Risk of Adverse Health Effects from Lunar Dust Exposure |url=https://humanresearchroadmap.nasa.gov/evidence/reports/lunar%20dust.pdf |access-date=December 8, 2022 |archive-date=December 4, 2021 |archive-url=https://web.archive.org/web/20211204004317/https://humanresearchroadmap.nasa.gov/evidence/reports/lunar%20dust.pdf |url-status=live}}</ref>]]
[[Ionizing radiation]] from [[cosmic ray]]s, their resulting [[neutron radiation]],<ref name="Science Mission Directorate 2005">{{cite web|date=September 8, 2005|title=Radioactive Moon|url=https://science.nasa.gov/science-news/science-at-nasa/2005/08sep_radioactivemoon#:~:text=Not%20so.,lunar%20surface%20itself%20is%20radioactive!|url-status=deviated|archive-url=https://web.archive.org/web/20191102123953/https://science.nasa.gov/science-news/science-at-nasa/2005/08sep_radioactivemoon/#:~:text=Not%20so.,lunar%20surface%20itself%20is%20radioactive!|archive-date=November 2, 2019|access-date=July 28, 2022|website=Science Mission Directorate}}</ref> and the Sun results in an average radiation level of 1.369 [[millisievert]]s per day during lunar [[daytime]],<ref name="surface-radiation"/> which is about 2.6 times more than the level on the [[International Space Station]], 5{{endash}}10 times more than the level during a trans-Atlantic flight, and 200 times more than the level on Earth's surface.<ref name="ScienceAlert 2020">{{cite web |date=September 26, 2020 |title=We Finally Know How Much Radiation There Is on The Moon, And It's Not Great News |url=https://www.sciencealert.com/scientists-predict-how-long-humans-can-survive-radiation-on-the-moon |url-status=live |archive-url=https://web.archive.org/web/20220728004319/https://www.sciencealert.com/scientists-predict-how-long-humans-can-survive-radiation-on-the-moon |archive-date=July 28, 2022 |access-date=July 28, 2022 |website=ScienceAlert}}</ref> For further comparison, radiation levels average about 1.84 millisieverts per day on a [[Human mission to Mars|flight to Mars]] and about 0.64 millisieverts per day on Mars itself, with some locations on Mars possibly having levels as low as 0.342 millisieverts per day.<ref name="Paris Davies Tognetti Zahniser 2020">{{cite arXiv |last1=Paris |first1=Antonio |last2=Davies |first2=Evan |last3=Tognetti |first3=Laurence |last4=Zahniser |first4=Carly |title=Prospective Lava Tubes at Hellas Planitia |date=April 27, 2020 |class=astro-ph.EP |eprint=2004.13156v1}}</ref><ref name="Wall 2013">{{cite web |last=Wall |first=Mike |date=December 9, 2013 |title=Radiation on Mars 'Manageable' for Manned Mission, Curiosity Rover Reveals |url=https://www.space.com/23875-mars-radiation-life-manned-mission.html |access-date=August 7, 2022 |website=Space.com |archive-date=December 15, 2020 |archive-url=https://web.archive.org/web/20201215082045/https://www.space.com/23875-mars-radiation-life-manned-mission.html |url-status=live}}</ref>
Solar radiation also [[static electricity|electrically charges]] the highly abrasive [[lunar dust]] and makes it levitate. This effect contributes to the easy spread of the sticky, lung- and gear-damaging lunar dust.<ref name="e657">{{cite web |title=The toxic side of the Moon |website=ESA |url=https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/The_toxic_side_of_the_Moon |access-date=2025-01-07}}</ref>

The Moon's [[axial tilt]] with respect to the [[ecliptic]] is only 1.5427°,<ref name="SolarViews" /><ref>{{Cite journal |last1=Rambaux |first1=N. |last2=Williams |first2=J. G. |date=2011 |title=The Moon's physical librations and determination of their free modes |url=https://doi.org/10.1007/s10569-010-9314-2 |url-status=live |journal=Celestial Mechanics and Dynamical Astronomy |volume=109 |issue=1 |pages=85–100 |bibcode=2011CeMDA.109...85R |doi=10.1007/s10569-010-9314-2 |archive-url=https://web.archive.org/web/20220730084921/https://link.springer.com/article/10.1007/s10569-010-9314-2 |archive-date=July 30, 2022 |access-date=July 30, 2022 |s2cid=45209988}}</ref> much less than the 23.44° of Earth. This small axial tilt means that the Moon's solar illumination varies much less with [[season]] than Earth's, and it also allows for the existence of some [[peaks of eternal light]] at the [[Lunar north pole|Moon's north pole]], at the rim of the crater [[Peary (crater)|Peary]].

The lunar surface is exposed to drastic temperature differences ranging from {{val|120|u=°C}} to {{val|−171|u=°C}} depending on the [[solar irradiance]].
Because of the lack of atmosphere, temperatures of different areas vary particularly upon whether they are in sunlight or shadow,<ref>{{cite web |last=Rocheleau |first=Jake |date=May 21, 2012 |title=Temperature on the Moon – Surface Temperature of the Moon |url=http://planetfacts.org/temperature-on-the-moon/ |url-status=live |archive-url=https://web.archive.org/web/20150527194737/http://planetfacts.org/temperature-on-the-moon/ |archive-date=May 27, 2015 |website=PlanetFacts.org}}</ref> making topographical details play a decisive role on local [[Global surface temperature|surface temperature]]s.<ref name="bbc" />
Parts of many craters, particularly the bottoms of many polar craters,<ref name="M03" /> are permanently shadowed. These [[crater of eternal darkness|craters of eternal darkness]] have extremely low temperatures. The ''Lunar Reconnaissance Orbiter'' measured the lowest summer temperatures in craters at the southern pole at {{Convert|35 |K |4=0 |abbr=on}}<ref>{{cite web |date=September 17, 2009 |title=Diviner News |url=http://www.diviner.ucla.edu/blog/?p=123 |url-status=dead |archive-url=https://web.archive.org/web/20100307031354/http://www.diviner.ucla.edu/blog/?p=123 |archive-date=March 7, 2010 |access-date=March 17, 2010 |publisher=[[UCLA]]}}</ref> and just {{Convert |26 |K |4=0 |abbr=on}} close to the winter solstice in the north polar crater [[Hermite (crater)|Hermite]]. This is the coldest temperature in the Solar System ever measured by a spacecraft, colder even than the surface of [[Pluto]].<ref name="bbc" />

Blanketed on top of the Moon's crust is a highly [[Comminution|comminuted]] (broken into ever smaller particles) and [[impact gardening|impact gardened]] mostly gray surface layer called [[regolith]], formed by impact processes. The finer regolith, the [[lunar soil]] of [[silicon dioxide]] glass, has a texture resembling snow and a scent resembling spent [[gunpowder]].<ref>{{cite web |date=January 30, 2006 |title=The Smell of Moondust |url=https://science.nasa.gov/headlines/y2006/30jan_smellofmoondust.htm |url-status=dead |archive-url=https://web.archive.org/web/20100308112332/http://science.nasa.gov/headlines/y2006/30jan_smellofmoondust.htm |archive-date=March 8, 2010 |access-date=March 15, 2010 |publisher=NASA}}</ref> The regolith of older surfaces is generally thicker than for younger surfaces: it varies in thickness from {{convert|10|{{endash}}|15|m|abbr=on}} in the highlands and {{convert|4|{{endash}}|5|m|abbr=on}} in the maria.<ref>{{cite book |last=Heiken |first=G. |url=https://archive.org/details/lunarsourcebooku0000unse/page/286 |title=Lunar Sourcebook, a user's guide to the Moon |date=1991 |publisher=[[Cambridge University Press]] |isbn=978-0-521-33444-0 |editor1-last=Vaniman |editor1-first=D. |location=New York |page=[https://archive.org/details/lunarsourcebooku0000unse/page/286 286] |access-date=December 17, 2019 |editor2-last=French |editor2-first=B. |archive-url=https://web.archive.org/web/20200617181609/https://archive.org/details/lunarsourcebooku0000unse/page/736 |archive-date=June 17, 2020 |url-status=live}}</ref> Beneath the finely comminuted regolith layer is the megaregolith, a layer of highly fractured bedrock many kilometers thick.<ref>{{cite journal |last=Rasmussen |first=K.L. |author2=Warren, P.H. |date=1985 |title=Megaregolith thickness, heat flow, and the bulk composition of the Moon |journal=[[Nature (journal)|Nature]] |volume=313 |issue=5998 |pages=121–124 |bibcode=1985Natur.313..121R |doi=10.1038/313121a0 |s2cid=4245137}}</ref>

These extreme conditions are considered to make it unlikely for spacecraft to harbor bacterial spores at the Moon for longer than just one lunar orbit.<ref>{{cite journal |last1=Schuerger |first1=Andrew C. |last2=Moores |first2=John E. |last3=Smith |first3=David J. |last4=Reitz |first4=Günther |date=June 2019 |title=A Lunar Microbial Survival Model for Predicting the Forward Contamination of the Moon |journal=Astrobiology |volume=19 |issue=6 |pages=730–756 |bibcode=2019AsBio..19..730S |doi=10.1089/ast.2018.1952 |pmid=30810338 |s2cid=73491587 |doi-access=free}}</ref>

===Surface features===
{{Main|Selenography|Lunar terrane|List of lunar features|List of quadrangles on the Moon}}
[[File:Apollo 17 AS17-140-21497.jpg|thumb|[[Apollo 17]] astronaut [[Harrison H. Schmitt]] next to the large Moon boulder nicknamed "[[Tracy's Rock]]"]]
The [[topography of the Moon]] has been measured with [[laser altimetry]] and [[stereoscopy|stereo image analysis]].<ref>{{cite journal |title=Topography of the South Polar Region from Clementine Stereo Imaging |last1=Spudis |first1=Paul D. |last2=Cook |first2=A. |last3=Robinson |first3=M. |last4=Bussey |first4=B. |last5=Fessler |first5=B. |bibcode=1998nvmi.conf...69S |journal=Workshop on New Views of the Moon: Integrated Remotely Sensed, Geophysical, and Sample Datasets |page=69 |date=January 1998}}</ref> Its most extensive [[List of features on the Moon|topographic feature]] is the giant far-side [[South Pole–Aitken basin]], some {{Convert|2240 |km |abbr=on}} in diameter, the largest crater on the Moon and the second-largest confirmed impact [[List of largest craters in the Solar System|crater in the Solar System]].<ref name="Spudis1994" /><ref>{{cite journal |doi=10.1029/97GL01718 |first1=C. M. |last1=Pieters |first2=S. |last2=Tompkins |first3=J. W. |last3=Head |first4=P. C. |last4=Hess |title=Mineralogy of the Mafic Anomaly in the South Pole-Aitken Basin: Implications for excavation of the lunar mantle |journal=[[Geophysical Research Letters]] |volume=24 |issue=15 |pages=1903–1906 |date=1997 |bibcode=1997GeoRL..24.1903P |hdl=2060/19980018038 |s2cid=128767066 |hdl-access=free}}</ref> At {{Convert |13 |km |abbr=on}} deep, its floor is the lowest point on the surface of the Moon,<ref name="Spudis1994" /><ref>{{cite journal |url=http://www.psrd.hawaii.edu/July98/spa.html |title=The Biggest Hole in the Solar System |page=20 |last=Taylor |first=G. J. |date=July 17, 1998 |journal=Planetary Science Research Discoveries |access-date=April 12, 2007 |url-status=live |archive-url=https://web.archive.org/web/20070820042129/http://www.psrd.hawaii.edu/July98/spa.html |archive-date=August 20, 2007 |bibcode=1998psrd.reptE..20T}}</ref> reaching {{convert|-9.178|km}} at {{coord|70.368|S|172.413|W|globe:moon_type:landmark|display=inline}} in a crater within [[Antoniadi (lunar crater)|Antoniadi crater]].<ref name="n402">{{cite journal | last1=Li | first1=ChunLai | last2=Ren | first2=Xin | last3=Liu | first3=JianJun | last4=Zou | first4=XiaoDuan | last5=Mu | first5=LingLi | last6=Wang | first6=JianYu | last7=Shu | first7=Rong | last8=Zou | first8=YongLiao | last9=Zhang | first9=HongBo | last10=Lü | first10=Chang | last11=Liu | first11=JianZhong | last12=Zuo | first12=Wei | last13=Su | first13=Yan | last14=Wen | first14=WeiBin | last15=Bian | first15=Wei | last16=Wang | first16=Min | last17=Xu | first17=Chun | last18=Kong | first18=DeQing | last19=Wang | first19=XiaoQian | last20=Wang | first20=Fang | last21=Geng | first21=Liang | last22=Zhang | first22=ZhouBin | last23=Zheng | first23=Lei | last24=Zhu | first24=XinYing | last25=Li | first25=JunDuo | last26=Ouyang | first26=ZiYuan | title=Laser altimetry data of Chang'E-1 and the global lunar DEM model | journal=Science China Earth Sciences | volume=53 | issue=11 | date=2010 | issn=1674-7313 | doi=10.1007/s11430-010-4020-1 | pages=1582–1593| bibcode=2010ScChD..53.1582L }}</ref> The [[List of tallest mountains in the Solar System|highest elevations]] of the Moon's surface, with the so-called [[Selenean summit]] at {{convert|10.629|km}} , are located directly to the northeast ({{coord|5.441|N|158.656|W|globe:moon_type:landmark|display=inline}}),<ref name="n402"/> which might have been thickened by the oblique formation impact of the South Pole–Aitken basin.<ref>{{cite journal |last=Schultz |first=P.H. |date=March 1997 |page=1259 |volume=28 |title=Forming the south-pole Aitken basin – The extreme games |journal=Conference Paper, 28th Annual Lunar and Planetary Science Conference |bibcode=1997LPI....28.1259S}}</ref> Other large impact basins such as [[Mare Imbrium|Imbrium]], [[Mare Serenitatis|Serenitatis]], [[Mare Crisium|Crisium]], [[Mare Smythii|Smythii]], and [[Mare Orientale|Orientale]] possess regionally low elevations and elevated rims.<ref name="Spudis1994" /> The far side of the lunar surface is on average about {{Convert |1.9 |km |abbr=on}} higher than that of the near side.<ref name="W06" />

The discovery of [[fault scarp]] cliffs suggest that the Moon has shrunk by about 90 metres (300&nbsp;ft) within the past billion years.<ref>{{cite web |publisher=NASA |title=NASA's LRO Reveals 'Incredible Shrinking Moon' |date=August 19, 2010 |url=http://www.nasa.gov/mission_pages/LRO/news/shrinking-moon.html |url-status=live |archive-url=https://web.archive.org/web/20100821124252/http://www.nasa.gov/mission_pages/LRO/news/shrinking-moon.html |archive-date=August 21, 2010}}</ref> Similar shrinkage features exist on [[Geology of Mercury|Mercury]]. Mare Frigoris, a basin near the north pole long assumed to be geologically dead, has cracked and shifted. Since the Moon does not have tectonic plates, its tectonic activity is slow, and cracks develop as it loses heat.<ref>{{Cite journal |last1=Watters |first1=Thomas R. |last2=Weber |first2=Renee C. |last3=Collins |first3=Geoffrey C. |last4=Howley |first4=Ian J. |last5=Schmerr |first5=Nicholas C. |last6=Johnson |first6=Catherine L. |date=June 2019 |title=Shallow seismic activity and young thrust faults on the Moon |journal=Nature Geoscience |publication-date=May 13, 2019 |volume=12 |issue=6 |pages=411–417 |doi=10.1038/s41561-019-0362-2 |bibcode=2019NatGe..12..411W |s2cid=182137223 |issn=1752-0894}}</ref>

Scientists have confirmed the presence of a cave on the Moon near the [[Sea of Tranquillity]], not far from the 1969 [[Apollo 11]] landing site. The cave, identified as an entry point to a collapsed lava tube, is roughly 45 meters wide and up to 80 m long. This discovery marks the first confirmed entry point to a lunar cave. The analysis was based on photos taken in 2010 by NASA's [[Lunar Reconnaissance Orbiter]]. The cave's stable temperature of around {{val|17|u=°C}} could provide a hospitable environment for future astronauts, protecting them from extreme temperatures, solar radiation, and micrometeorites. However, challenges include accessibility and risks of avalanches and cave-ins. This discovery offers potential for future lunar bases or emergency shelters.<ref>{{Cite web |date=July 18, 2024 |title=Cave on the Moon: What this discovery means for space exploration |url=https://indianexpress.com/article/explained/everyday-explainers/cave-on-the-moon-explained-9459805/ |access-date=July 19, 2024 |website=The Indian Express |language=en}}</ref>

==== Volcanic features ====
{{Main |Volcanism on the Moon}}
[[File:Moon names.svg|thumb|upright=1.35|The names of the main volcanic features, the [[lunar mare|maria]] (blue), and of some [[lunar craters|craters]] (brown) of the near side of the Moon]]
The main features visible from Earth by the naked eye are dark and relatively featureless lunar plains called ''[[lunar mare|maria]]'' (singular ''mare''; [[Latin]] for "seas", as they were once believed to be filled with water)<ref>{{cite book |author=Wlasuk, Peter |title=Observing the Moon |url=https://books.google.com/books?id=TWtLIOlPwS4C |date=2000 |publisher=[[Springer Science+Business Media|Springer]] |isbn=978-1-85233-193-1 |page=19}}</ref> are vast solidified pools of ancient [[basalt]]ic lava. Although similar to terrestrial basalts, lunar basalts have more iron and no minerals altered by water.<ref>{{cite web |url=http://www.psrd.hawaii.edu/April04/lunarAnorthosites.html |title=The Oldest Moon Rocks |last=Norman |first=M. |work=Planetary Science Research Discoveries |publisher=Hawai'i Institute of Geophysics and Planetology |date=April 21, 2004 |access-date=April 12, 2007 |url-status=live |archive-url=https://web.archive.org/web/20070418152325/http://www.psrd.hawaii.edu/April04/lunarAnorthosites.html |archive-date=April 18, 2007}}</ref> The majority of these lava deposits erupted or flowed into the depressions associated with [[impact basins]], though the Moon's largest expanse of basalt flooding, [[Oceanus Procellarum]], does not correspond to an obvious impact basin. Different episodes of lava flow in maria can often be recognized by variations in surface albedo and distinct flow margins.<ref>{{cite journal |last1=Friedman |first1=R.C. |last2=Blewett |first2=D. T. |last3=Taylor |first3=G.J. |last4=Lucey |first4=P. G. |year=1996 |title=FeO and TiO2 Variations in Mare Imbrium |journal=Lunar and Planetary Science |volume=27 |pages=383 |bibcode=1996LPI....27..383F |url=https://adsabs.harvard.edu/full/1996LPI....27..383F}}</ref>

As the maria formed, cooling and contraction of the basaltic lava created [[wrinkle ridge]]s in some areas. These low, sinuous ridges can extend for hundreds of kilometers and often outline buried structures within the mare. Another result of maria formation is the creation of concentric depressions along the edges, known as [[rille|arcuate rilles]]. These features occur as the mare basalts sink inward under their own weight, causing the edges to fracture and separate.

In addition to the visible maria, the Moon has mare deposits covered by ejecta from impacts. Called cryptomares, these hidden mares are likely older than the exposed ones.<ref>{{cite journal |last1=Izquierdo |first1=Kristel |last2=Sori |first2=M. M. |last3=Checketts |first3=B. |last4=Hampton |first4=I. |last5=Johnson |first5=B.C. |last6=Soderblom |first6=J.M. |year=2024 |title=Global Distribution and Volume of Cryptomare and Visible Mare on the Moon From Gravity and Dark Halo Craters |journal=Journal of Geophysical Research: Planets |volume=129 |issue=2 |doi=10.1029/2023JE007867 |bibcode=2024JGRE..12907867I |doi-access=free}}</ref> Conversely, mare lava has obscured many impact melt sheets and pools. Impact melts are formed when intense shock pressures from collisions vaporize and melt zones around the impact site. Where still exposed, impact melt can be distinguished from mare lava by its distribution, albedo, and texture.<ref>{{cite journal |last1=Spudis |first1=Paul |year=2016 |title=Mapping Melts on the Moon |journal=Smithsonian Air and Space Magazine |url=https://www.smithsonianmag.com/air-space-magazine/mapping-melted-moon-180958645/}}</ref>

[[Sinuous rilles]], found in and around maria, are likely extinct [[lava channels]] or collapsed [[lava tubes]]. They typically originate from volcanic [[Volcanism on the Moon|vents]], meandering and sometimes branching as they progress. The largest examples, such as [[Schroter's Valley]] and [[Hadley–Apennine|Rima Hadley]], are significantly longer, wider, and deeper than terrestrial lava channels, sometimes featuring bends and sharp turns that again, are uncommon on Earth.

Mare volcanism has altered impact craters in various ways, including filling them to varying degrees, and raising and fracturing their floors from uplift of mare material beneath their interiors. Examples of such craters include [[Taruntius (crater)|Taruntius]] and [[Gassendi (crater)|Gassendi]]. Some craters, such as [[Hyginus (crater)|Hyginus]], are of wholly volcanic origin, forming as [[caldera]]s or [[pit crater|collapse pits]]. Such craters are relatively rare and tend to be smaller (typically a few kilometers wide), shallower, and more irregularly shaped than impact craters. They also lack the upturned rims characteristic of impact craters.

Several [[geologic province]]s containing [[shield volcano]]es and volcanic [[lunar dome|domes]] are found within the near side maria.<ref>{{cite journal |last1=Wilson |first1=Lionel |last2=Head |first2=James W. |title=Lunar Gruithuisen and Mairan domes: Rheology and mode of emplacement |journal=[[Journal of Geophysical Research]] |date=2003 |volume=108 |url=http://www.agu.org/pubs/crossref/2003/2002JE001909.shtml |access-date=April 12, 2007 |issue=E2 |doi=10.1029/2002JE001909 |page=5012 |bibcode=2003JGRE..108.5012W |citeseerx=10.1.1.654.9619 |s2cid=14917901 |url-status=live |archive-url=https://web.archive.org/web/20070312071105/http://www.agu.org/pubs/crossref/2003/2002JE001909.shtml |archive-date=March 12, 2007}}</ref> There are also some regions of [[pyroclastic rock|pyroclastic deposits]], [[scoria cones]] and [[volcanism on the Moon|non-basaltic domes]] made of particularly high viscosity lava.

Almost all maria are on the near side of the Moon, and cover 31% of the surface of the near side<ref name="worldbook" /> compared with 2% of the far side.<ref>{{cite journal |last1=Gillis |first1=J. J. |last2=Spudis |first2=P. D. |title=The Composition and Geologic Setting of Lunar Far Side Maria |journal=[[Lunar and Planetary Science]] |date=1996 |volume=27 |page=413 |bibcode=1996LPI....27..413G}}</ref> This is likely due to a [[KREEP|concentration of heat-producing elements]] under the crust on the near side, which would have caused the underlying mantle to heat up, partially melt, rise to the surface and erupt.<ref name="S06" /><ref>{{cite journal |title=Global Elemental Maps of the Moon: The Lunar Prospector Gamma-Ray Spectrometer |last1=Lawrence |first1=D. J. |last2=Feldman |first2=W. C. |last3=Barraclough |first3=B. L. |last4=Binder |first4=A. B. |last5=Elphic |first5=R. C. |last6=Maurice |first6=S. |last7=Thomsen |first7=D. R. |journal=[[Science (journal)|Science]] |volume=281 |issue=5382 |pages=1484–1489 |doi=10.1126/science.281.5382.1484 |date=August 11, 1998 |pmid=9727970 |bibcode=1998Sci...281.1484L |doi-access=free}}</ref><ref>{{cite journal |url=http://www.psrd.hawaii.edu/Aug00/newMoon.html |title=A New Moon for the Twenty-First Century |page=41 |last=Taylor |first=G. J. |journal=Planetary Science Research Discoveries |date=August 31, 2000 |access-date=April 12, 2007 |url-status=live |archive-url=https://web.archive.org/web/20120301074958/http://www.psrd.hawaii.edu/Aug00/newMoon.html |archive-date=March 1, 2012 |bibcode=2000psrd.reptE..41T}}</ref> Most of the Moon's [[lunar mare|mare basalts]] erupted during the [[Imbrian|Imbrian period]], 3.3–3.7&nbsp;billion years ago, though some being as young as 1.2&nbsp;billion years<ref name="Hiesinger" /> and as old as 4.2&nbsp;billion years.<ref name="Papike" />

[[File:Lava flows in Mare Imbrium (AS15-M-1558).png|thumb|Old [[basalt|hardened]] lava flows of [[Mare Imbrium]] forming [[wrinkle ridge]]s]]

In 2006, a study of [[Ina (crater)|Ina]], a tiny depression in [[Lacus Felicitatis]], found jagged, relatively dust-free features that, because of the lack of erosion by infalling debris, appeared to be only 2 million years old.<ref name=Berardelli>{{cite journal |url=https://www.science.org/content/article/long-live-moon |title=Long Live the Moon! |journal=[[Science (journal)|Science]] |date=November 9, 2006 |author=Phil Berardelli |url-status=live |archive-url=https://web.archive.org/web/20141018153016/http://news.sciencemag.org/2006/11/long-live-moon |archive-date=October 18, 2014 |access-date=October 14, 2014}}</ref> [[Moonquake]]s and releases of gas indicate continued lunar activity.<ref name="Berardelli"/> Evidence of recent lunar volcanism has been identified at 70 [[irregular mare patch]]es, some less than 50 million years old. This raises the possibility of a much warmer lunar mantle than previously believed, at least on the near side where the deep crust is substantially warmer because of the greater concentration of radioactive elements.<ref>{{cite web |url=http://news.discovery.com/space/imps-reveal-volcanoes-erupted-recently-on-the-moon-141014.htm |title=Volcanoes Erupted 'Recently' on the Moon |publisher=[[Discovery News]] |date=October 14, 2014 |author=Jason Major |url-status=live |archive-url=https://web.archive.org/web/20141016190653/http://news.discovery.com/space/imps-reveal-volcanoes-erupted-recently-on-the-moon-141014.htm |archive-date=October 16, 2014}}</ref><ref>{{cite web |url=http://www.nasa.gov/press/2014/october/nasa-mission-finds-widespread-evidence-of-young-lunar-volcanism/#.VDxNw0t3uxo |title=NASA Mission Finds Widespread Evidence of Young Lunar Volcanism |publisher=NASA |date=October 12, 2014 |url-status=live |archive-url=https://web.archive.org/web/20150103095208/http://www.nasa.gov/press/2014/october/nasa-mission-finds-widespread-evidence-of-young-lunar-volcanism/#.VDxNw0t3uxo |archive-date=January 3, 2015}}</ref><ref>{{cite journal |url=https://www.science.org/content/article/recent-volcanic-eruptions-moon |title=Recent volcanic eruptions on the moon |journal=[[Science (journal)|Science]] |date=October 12, 2014 |author=Eric Hand |url-status=live |archive-url=https://web.archive.org/web/20141014092239/http://news.sciencemag.org/space/2014/10/recent-volcanic-eruptions-moon |archive-date=October 14, 2014}}</ref><ref>{{cite journal |title=Evidence for basaltic volcanism on the Moon within the past 100 million years |journal=[[Nature Geoscience]] |last1=Braden |first1=S.E. |last2=Stopar |first2=J.D. |last3=Robinson |first3=M.S. |last4=Lawrence |first4=S.J. |last5=van der Bogert |first5=C.H. |last6=Hiesinger |first6=H. |volume=7 |issue=11 |pages=787–791 |bibcode=2014NatGe...7..787B |doi=10.1038/ngeo2252 |year=2014}}</ref> Evidence has been found for 2–10 million years old basaltic volcanism within the crater Lowell,<ref>{{cite journal |last1=Srivastava |first1=N. |last2=Gupta |first2=R.P. |year=2013 |title=Young viscous flows in the Lowell crater of Orientale basin, Moon: Impact melts or volcanic eruptions? |journal=[[Planetary and Space Science]] |volume=87 |pages=37–45 |doi=10.1016/j.pss.2013.09.001 |bibcode=2013P&SS...87...37S}}</ref><ref>{{cite journal |last1=Gupta |first1=R.P. |last2=Srivastava |first2=N. |last3=Tiwari |first3=R.K. |year=2014 |title=Evidences of relatively new volcanic flows on the Moon |journal=[[Current Science]] |volume=107 |issue=3 |pages=454–460 |jstor=24103498}}</ref> inside the Orientale basin. Some combination of an initially hotter mantle and local enrichment of heat-producing elements in the mantle could be responsible for prolonged activities on the far side in the Orientale basin.<ref>{{cite journal |last1=Whitten |first1=Jennifer |last2=Head |first2=James W. |last3=Staid |first3=Matthew |last4=Pieters |first4=Carle M. |last5=Mustard |first5=John |last6=Clark |first6=Roger |last7=Nettles |first7=Jeff |last8=Klima |first8=Rachel L. |last9=Taylor |first9=Larry |year=2011 |title=Lunar mare deposits associated with the Orientale impact basin: New insights into mineralogy, history, mode of emplacement, and relation to Orientale Basin evolution from Moon Mineralogy Mapper (M3) data from Chandrayaan-1 |journal=[[Journal of Geophysical Research]] |volume=116 |page=E00G09 |doi=10.1029/2010JE003736 |bibcode=2011JGRE..116.0G09W |s2cid=7234547 |doi-access=free}}</ref><ref>{{cite journal |last1=Cho |first1=Y. |display-authors=etal |year=2012 |title=Young mare volcanism in the Orientale region contemporary with the Procellarum KREEP Terrane (PKT) volcanism peak period 2 b.y. ago |journal=[[Geophysical Research Letters]] |volume=39 |issue=11 |page=L11203 |bibcode=2012GeoRL..3911203C |doi=10.1029/2012GL051838 |s2cid=134074700}}</ref>

The lighter-colored regions of the Moon are called ''terrae'', or more commonly ''highlands'', because they are higher than most maria. They have been radiometrically dated to having formed 4.4&nbsp;billion years ago and may represent [[plagioclase]] [[cumulates]] of the lunar magma ocean.<ref name="Hiesinger" /><ref name="Papike" /> In contrast to Earth, no major lunar mountains are believed to have formed as a result of tectonic events.<ref>{{cite web |last=Munsell |first=K. |publisher=NASA |work=Solar System Exploration |title=Majestic Mountains |url=http://sse.jpl.nasa.gov/educ/themes/display.cfm?Item=mountains |date=December 4, 2006 |access-date=April 12, 2007 |url-status=dead |archive-url=https://web.archive.org/web/20080917055643/http://sse.jpl.nasa.gov/educ/themes/display.cfm?Item=mountains |archive-date=September 17, 2008}}</ref>

The concentration of maria on the near side likely reflects the substantially thicker crust of the highlands of the Far Side, which may have formed in a slow-velocity impact of a second moon of Earth a few tens of millions of years after the Moon's formation.<ref>{{cite journal |author=Richard Lovett |url=http://www.nature.com/news/2011/110803/full/news.2011.456.html#B1 |title=Early Earth may have had two moons : Nature News |journal=Nature |access-date=November 1, 2012 |url-status=live |archive-url=https://web.archive.org/web/20121103145236/http://www.nature.com/news/2011/110803/full/news.2011.456.html#B1 |archive-date=November 3, 2012 |doi=10.1038/news.2011.456 |year=2011 |doi-access=free}}</ref><ref>{{cite web |url=http://theconversation.edu.au/was-our-two-faced-moon-in-a-small-collision-2659 |title=Was our two-faced moon in a small collision? |publisher=Theconversation.edu.au |access-date=November 1, 2012 |url-status=dead |archive-url=https://web.archive.org/web/20130130004522/http://theconversation.edu.au/was-our-two-faced-moon-in-a-small-collision-2659 |archive-date=January 30, 2013}}</ref> Alternatively, it may be a consequence of asymmetrical [[tidal heating]] when the Moon was much closer to the Earth.<ref>{{cite journal |title=Near/far side asymmetry in the tidally heated Moon |last1=Quillen |first1=Alice C. |last2=Martini |first2=Larkin |last3=Nakajima |first3=Miki |journal=Icarus |volume=329 |pages=182–196 |date=September 2019 |doi=10.1016/j.icarus.2019.04.010 |pmid=32934397 |pmc=7489467 |arxiv=1810.10676 |bibcode=2019Icar..329..182Q}}</ref>

====Impact craters====
{{Further |List of craters on the Moon}}
[[File:Daedalus crater AS11-41-6151.jpg|alt=A gray, many-ridged surface from high above. The largest feature is a circular ringed structure with high walled sides and a lower central peak: the entire surface out to the horizon is filled with similar structures that are smaller and overlapping.|thumb|A view of a three-kilometer-deep larger crater [[Daedalus (crater)|Daedalus]] on the [[Far side of the Moon|Moon's far side]]]]
A major geologic process that has affected the Moon's surface is [[impact crater]]ing,<ref>{{cite book |last=Melosh |first=H. J. |title=Impact cratering: A geologic process |date=1989 |publisher=[[Oxford University Press]] |isbn=978-0-19-504284-9}}</ref> with craters formed when asteroids and comets collide with the lunar surface. There are estimated to be roughly 300,000 craters wider than {{Convert |1 |km |4=1 |abbr=on}} on the Moon's near side.<ref>{{cite web |title=Moon Facts |url=http://planck.esa.int/science-e/www/object/index.cfm?fobjectid=31412 |work=SMART-1 |publisher=[[European Space Agency]] |date=2010 |access-date=May 12, 2010 |archive-date=March 17, 2012 |archive-url=https://web.archive.org/web/20120317004513/http://planck.esa.int/science-e/www/object/index.cfm?fobjectid=31412 |url-status=dead}}</ref> Lunar craters exhibit a variety of forms, depending on their size. In order of increasing diameter, the basic types are simple craters with smooth bowl shaped interiors and upturned rims, [[complex crater]]s with flat floors, terraced walls and central peaks, [[peak ring]] basins, and [[multi-ring basin]]s with two or more concentric rings of peaks.<ref>[https://www.lpi.usra.edu/exploration/education/hsResearch/moon_101/ImpactCratering.pdf Impact Cratering Notes (LPI)]</ref> The vast majority of impact craters are circular, but some, like [[Cantor (crater)|Cantor]] and [[Janssen (lunar crater)|Janssen]], have more polygonal outlines, possibly guided by underlying faults and joints. Others, such as the [[Messier (crater)|Messier]] pair, [[Schiller (crater)|Schiller]], and [[Daniell (crater)|Daniell]], are elongated. Such elongation can result from highly oblique impacts, [[binary asteroid]] impacts, fragmentation of impactors before surface strike, or closely spaced [[secondary crater|secondary]] impacts.<ref>{{cite journal |last1=Herrick |first1=R.R. |last2=Forsberg-Taylor |first2=N. K. |year=2003 |title=The shape and appearance of craters formed by oblique impact on the Moon and Venus |journal=Meteoritics & Planetary Science |volume=38 |issue=11 |pages=1551–1578 |doi=10.1111/j.1945-5100.2003.tb00001.x |bibcode=2003M&PS...38.1551H |url=https://onlinelibrary.wiley.com/doi/pdfdirect/10.1111/j.1945-5100.2003.tb00001.x}}</ref>

The [[lunar geologic timescale]] is based on the most prominent impact events, such as multi-ring formations like [[Nectarian|Nectaris]], [[Lower Imbrian|Imbrium]], and [[Mare Orientale|Orientale]] that are between hundreds and thousands of kilometers in diameter and associated with a broad apron of ejecta deposits that form a regional [[stratigraphy|stratigraphic horizon]].<ref name="geologic" /> The lack of an atmosphere, weather, and recent geological processes mean that many of these craters are well-preserved. Although only a few [[multi-ring basins]] have been definitively dated, they are useful for assigning relative ages. Because impact craters accumulate at a nearly constant rate, counting the number of craters per unit area can be used to estimate the age of the surface.<ref name="geologic" />
However care needs to be exercised with the [[crater counting]] technique due to the potential presence of [[secondary crater]]s. Ejecta from impacts can create secondary craters that often appear in clusters or chains but can also occur as isolated formations at a considerable distance from the impact. These can resemble primary craters, and may even dominate small crater populations, so their unidentified presence can distort age estimates.<ref>{{cite journal |last1=Xiao |first1=Z. |last2=Strom |first2=R.G. |year=2012 |title=Problems determining relative and absolute ages using the small crater population |journal=Icarus |volume=220 |issue=1 |pages=254–267 |doi=10.1016/j.icarus.2012.05.012 |bibcode=2012Icar..220..254X |url=https://www.uni-muenster.de/imperia/md/content/planetology/lectures/ss2015/143897-hottopics/xiao_and_strom_2012.pdf}}</ref>

The radiometric ages of impact-melted rocks collected during the [[Apollo missions]] cluster between 3.8 and 4.1&nbsp;billion years old: this has been used to propose a [[Late Heavy Bombardment]] period of increased impacts.<ref>{{cite journal |last1=Hartmann |first1=William K. |last2=Quantin |first2=Cathy |last3=Mangold |first3=Nicolas |date=2007 |volume=186 |issue=1 |pages=11–23 |journal=[[Icarus (journal)|Icarus]] |title=Possible long-term decline in impact rates: 2. Lunar impact-melt data regarding impact history |doi=10.1016/j.icarus.2006.09.009 |bibcode=2007Icar..186...11H}}</ref>

High-resolution images from the Lunar Reconnaissance Orbiter in the 2010s show a contemporary crater-production rate significantly higher than was previously estimated. A secondary cratering process caused by [[distal ejecta]] is thought to churn the top two centimeters of regolith on a timescale of 81,000 years.<ref>{{cite web |url=https://www.newscientist.com/article/2108929-the-moon-has-hundreds-more-craters-than-we-thought/ |title=The moon has hundreds more craters than we thought |first=Rebecca |last=Boyle |url-status=live |archive-url=https://web.archive.org/web/20161013143743/https://www.newscientist.com/article/2108929-the-moon-has-hundreds-more-craters-than-we-thought/ |archive-date=October 13, 2016}}</ref><ref>{{cite journal |title=Quantifying crater production and regolith overturn on the Moon with temporal imaging |first1=Emerson J. |last1=Speyerer |first2=Reinhold Z. |last2=Povilaitis |first3=Mark S. |last3=Robinson |first4=Peter C. |last4=Thomas |first5=Robert V. |last5=Wagner |date=October 13, 2016 |journal=[[Nature (journal)|Nature]] |volume=538 |issue=7624 |pages=215–218 |doi=10.1038/nature19829 |pmid=27734864 |bibcode=2016Natur.538..215S |s2cid=4443574}}</ref> This rate is 100 times faster than the rate computed from models based solely on direct micrometeorite impacts.<ref>{{cite web |title=Earth's Moon Hit by Surprising Number of Meteoroids |date=October 13, 2016 |publisher=NASA |url=https://www.nasa.gov/press-release/goddard/2016/lro-lunar-cratering |access-date=May 21, 2021 |archive-date=July 2, 2022 |archive-url=https://web.archive.org/web/20220702225136/https://www.nasa.gov/press-release/goddard/2016/lro-lunar-cratering/ |url-status=live}}</ref>

====Lunar swirls====
{{Main|Lunar swirls}}
[[File:Reiner-gamma-clem1.jpg|thumb|Wide-angle image of a lunar swirl, the 70-kilometer-long [[Reiner Gamma]]]]
Lunar swirls are enigmatic features found across the Moon's surface. They are characterized by a high albedo, appear optically immature (i.e. the optical characteristics of a relatively young [[regolith]]), and often have a sinuous shape. Their shape is often accentuated by low [[albedo]] regions that wind between the bright swirls. They are located in places with enhanced surface [[magnetic field]]s and many are located at the [[antipodal point]] of major impacts. Well known swirls include the [[Reiner Gamma]] feature and [[Mare Ingenii]]. They are hypothesized to be areas that have been partially shielded from the [[solar wind]], resulting in slower [[space weathering]].<ref>{{cite journal |title=Reflectance spectra of seven lunar swirls examined by statistical methods: A space weathering study |last1=Chrbolková |first1=Kateřina |last2=Kohout |first2=Tomáš |last3=Ďurech |first3=Josef |journal=Icarus |volume=333 |pages=516–527 |date=November 2019 |doi=10.1016/j.icarus.2019.05.024 |bibcode=2019Icar..333..516C |doi-access=free}}</ref>

=== 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>