Editing Carbon monoxide (section)

=== Astronomy ===
Beyond Earth, carbon monoxide is the second-most common diatomic molecule in the [[interstellar medium]], after [[molecular hydrogen]].  Because of its asymmetry, this [[polar molecule]] produces far brighter [[spectral line]]s than the hydrogen molecule, making CO much easier to detect.  Interstellar CO was first detected with [[radio telescope]]s in 1970. It is now the most commonly used tracer of molecular gas in general in the interstellar medium of galaxies, as molecular hydrogen can only be detected using ultraviolet light, which requires [[space telescopes]]. Carbon monoxide observations provide much of the information about the [[molecular cloud]]s in which most [[star formation|stars form]].<ref>{{cite journal |author=Combes, Françoise |year=1991 |title=Distribution of CO in the Milky Way |journal=Annual Review of Astronomy & Astrophysics |volume=29 |pages=195–237 |bibcode=1991ARA&A..29..195C |doi=10.1146/annurev.aa.29.090191.001211}}</ref><ref>{{cite journal |author=Hamed, M. |year=2021 |title=Multiwavelength dissection of a massive heavily dust-obscured galaxy and its blue companion at z~2 |journal=Astronomy & Astrophysics |volume=646 |pages=A127 |arxiv=2101.07724 |bibcode=2021A&A...646A.127H |doi=10.1051/0004-6361/202039577 |s2cid=231639096}}</ref>

[[Beta Pictoris]], the second brightest star in the constellation [[Pictor]], shows an [[infrared excess|excess of infrared emission]] compared to normal stars of its type, which is caused by large quantities of dust and gas (including carbon monoxide)<ref name="LAT-20140308">{{cite news |last=Khan |first=Amina |title=Did two planets around nearby star collide? Toxic gas holds hints |url=http://www.latimes.com/science/sciencenow/la-sci-sn-beta-pictoris-star-planet-gas-collision-comets-carbon-monoxide-20140307,0,1884709.story |access-date=March 9, 2014 |work=[[Los Angeles Times]]}}</ref><ref name="SCI-20140306">{{cite journal |vauthors=Dent, WR, Wyatt, MC, Roberge, A, Augereau, JC, Casassus, S, Corder, S, Greaves, JS, ((de Gregorio-Monsalvo, I)), Hales, A, Jackson, AP, Hughes, AM, Meredith A, Lagrange, AM, Matthews, B, Wilner, D |date=March 6, 2014 |title=Molecular Gas Clumps from the Destruction of Icy Bodies in the β Pictoris Debris Disk |url=https://www.science.org/doi/abs/10.1126/science.1248726 |journal=[[Science (journal)|Science]] |volume=343 |issue=6178 |pages=1490–1492 |arxiv=1404.1380 |bibcode=2014Sci...343.1490D |doi=10.1126/science.1248726 |pmid=24603151 |s2cid=206553853 |access-date=March 9, 2014}}</ref> near the star.

In the [[atmosphere of Venus]] carbon monoxide occurs as a result of the photodissociation of carbon dioxide by electromagnetic radiation of wavelengths shorter than 169 [[nanometre|nm]]. It has also been identified spectroscopically on the surface of Neptune's moon [[Triton (moon)|Triton]].<ref name="Lellouchde Bergh2010">{{cite journal |last1=Lellouch |first1=E. |last2=de Bergh |first2=C. |last3=Sicardy |first3=B. |last4=Ferron |first4=S. |last5=Käufl |first5=H.-U. |year=2010 |title=Detection of CO in Triton's atmosphere and the nature of surface-atmosphere interactions |journal=Astronomy and Astrophysics |volume=512 |pages=L8 |arxiv=1003.2866 |bibcode=2010A&A...512L...8L |doi=10.1051/0004-6361/201014339 |issn=0004-6361 |s2cid=58889896}}</ref>

Solid carbon monoxide is a component of [[comet]]s.<ref>{{cite journal |last1=Greenberg |first1=J. Mayo |date=1998 |title=Making a comet nucleus |journal=Astronomy and Astrophysics |volume=330 |pages=375 |bibcode=1998A&A...330..375G}}</ref> The [[Volatile (astrogeology)|volatile or "ice"]] component of [[Halley's Comet]] is about 15% CO.<ref name="Yeomans">{{cite web |last=Yeomans |first=Donald K. |date=2005 |title=Comets (World Book Online Reference Center 125580) |url=http://www.nasa.gov/worldbook/comet_worldbook.html |url-status=dead |archive-url=https://web.archive.org/web/20050429084558/http://www.nasa.gov/worldbook/comet_worldbook.html |archive-date=29 April 2005 |access-date=18 August 2022 |publisher=NASA |quote=About 80 percent of the ice is water ice, and frozen carbon monoxide makes up another 15 percent. |df=dmy-all}}</ref> At room temperature and at atmospheric pressure, carbon monoxide is actually only metastable (see [[Boudouard reaction]]) and the same is true at low temperatures where CO and {{chem2|CO2}} are solid, but nevertheless it can exist for billions of years in comets. There is very little CO in the atmosphere of [[Pluto]], which seems to have been formed from comets. This may be because there is (or was) liquid water inside Pluto.

Carbon monoxide can react with water to form carbon dioxide and hydrogen:
:{{chem2|CO + H2O -> H2 + CO2}}

This is called the [[water-gas shift reaction]] when occurring in the gas phase, but it can also take place (very slowly) in an aqueous solution.
If the hydrogen partial pressure is high enough (for instance in an underground sea), [[formic acid]] will be formed:
:{{chem2|CO + H2O -> HCOOH}}

These reactions can take place in a few million years even at temperatures such as found on Pluto.<ref>{{cite journal |last1=Christopher Glein and Hunter Waite |date=May 11, 2018 |title=Primordial N2 provides a cosmo chemical explanation for the existence of Sputnik Planitia, Pluto |journal=Icarus |volume=313 |pages=79–92 |arxiv=1805.09285 |bibcode=2018Icar..313...79G |doi=10.1016/j.icarus.2018.05.007 |s2cid=102343522}}</ref>