Editing Moon (section)

=== 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>