Editing Hydrogen cyanide (section)

=== On Titan ===
HCN has been measured in [[Atmosphere of Titan|Titan's atmosphere]] by four instruments on the [[Cassini–Huygens|Cassini space probe]], one instrument on [[Voyager 1|Voyager]], and one instrument on Earth.<ref>{{Cite journal| vauthors = Loison JC, Hébrard E, Dobrijevic M, Hickson KM, Caralp F, Hue V, Gronoff G, Venot O, Bénilan Y | display-authors = 6 |date=February 2015|title=The neutral photochemistry of nitriles, amines and imines in the atmosphere of Titan|journal=Icarus|volume=247|pages=218–247|doi=10.1016/j.icarus.2014.09.039|bibcode=2015Icar..247..218L|url=https://lirias.kuleuven.be/handle/123456789/486735}}</ref> One of these measurements was ''in situ'', where the Cassini spacecraft dipped between {{cvt|1000 and 1100|km}} above Titan's surface to collect atmospheric gas for [[mass spectrometry]] analysis.<ref>{{Cite journal| vauthors = Magee BA, Waite JH, Mandt KE, Westlake J, Bell J, Gell DA |date=December 2009|title=INMS-derived composition of Titan's upper atmosphere: Analysis methods and model comparison|journal=Planetary and Space Science|volume=57|issue=14–15|pages=1895–1916|doi=10.1016/j.pss.2009.06.016|bibcode=2009P&SS...57.1895M}}</ref> HCN initially forms in Titan's atmosphere through the reaction of photochemically produced methane and nitrogen radicals which proceed through the H<sub>2</sub>CN intermediate, e.g., (CH<sub>3</sub> + N → H<sub>2</sub>CN + H → HCN + H<sub>2</sub>).<ref name="pearce2020">{{cite journal | vauthors = Pearce BK, Molaverdikhani K, Pudritz RE, Henning T, Hébrard E |title=HCN Production in Titan's Atmosphere: Coupling Quantum Chemistry and Disequilibrium Atmospheric Modeling |journal=Astrophysical Journal |year=2020 |volume=901 |issue=2 |page=110 |doi=10.3847/1538-4357/abae5c |arxiv=2008.04312 |bibcode=2020ApJ...901..110P |s2cid=221095540 |doi-access=free }}</ref><ref>{{cite journal | vauthors = Pearce BK, Ayers PW, Pudritz RE | title = A Consistent Reduced Network for HCN Chemistry in Early Earth and Titan Atmospheres: Quantum Calculations of Reaction Rate Coefficients | journal = The Journal of Physical Chemistry A | volume = 123 | issue = 9 | pages = 1861–1873 | date = March 2019 | pmid = 30721064 | doi = 10.1021/acs.jpca.8b11323 | arxiv = 1902.05574 | s2cid = 73442008 | bibcode = 2019JPCA..123.1861P }}</ref> Ultraviolet radiation breaks HCN up into CN + H; however, CN is efficiently recycled back into HCN via the reaction CN + CH<sub>4</sub> → HCN + CH<sub>3</sub>.<ref name="pearce2020" />