<p>How common is H2 forming under a shell of normal ice, among comets?</p>
<p>The context is the Oumuamua discussion, and its latest tentative solution. &quot;Acceleration of 1I/‘Oumuamua from radiolytically produced H2 in H2O ice&quot; <a href="https://www.nature.com/articles/s41586-022-05687-w" rel="nofollow noreferrer">https://www.nature.com/articles/s41586-022-05687-w</a></p>
<p>Is formation of H2 in comets has discussed for long &quot;The possible formation of a hydrogen coma around comets at large heliocentric distances&quot; <a href="https://ui.adsabs.harvard.edu/abs/1988ApJ...324L..31B/abstract" rel="nofollow noreferrer">https://ui.adsabs.harvard.edu/abs/1988ApJ...324L..31B/abstract</a></p>
<p>...but has it been observed before? Or is Oumuamua perhaps its first observation?</p>

CC BY-SA 4.0
2023-03-23T11:33:22.290Z
It's never been observed, that's the problem. Hydrogen is invisible at temperature below several thousand K.
AtmosphericPrisonEscape
CC BY-SA 4.0
2023-03-23T17:34:01.333Z
Do you have access to the text of the nature article? Their first three paragraphs outline how a) H2 is non-detectable in the wavelengths that were observed and b) gives a list of laboratory experiments that show H2 production in porous H2O ices in lab settings.
AtmosphericPrisonEscape
CC BY-SA 4.0
2023-03-24T12:42:03.800Z
@AtmosphericPrisonEscape "Hydrogen is invisible at temperature below several thousand K." Maybe in visible, but what about far infrared and radio?
uhoh
CC BY-SA 4.0
2023-03-24T13:10:51.373Z
@AtmosphericPrisonEscape  Unfortunately not, but their datasets are open "The datasets generated and analysed during the current study are available on GitHub at https://github.com/bergnerjb/Oumuamua_H2."
Mark Besser
CC BY-SA 4.0
2023-03-24T14:40:32.440Z
@MarkBesser The data they are analysing there, are the trajectories of the object under the presumed hydrogen outgassing, which they model using the code Mercury. The data generated and available is that simulation data. So those are not experimental datasets.
You could try "other sources" on the internet *cough* to get your hands on this article...
AtmosphericPrisonEscape
CC BY-SA 4.0
2023-03-24T14:50:12.550Z
@uhoh Quadrupole and spin-transitions are way too faint to measure $H_2$ outgassing from comets, they are even too faint to measure protoplanetary disc masses.
AtmosphericPrisonEscape
CC BY-SA 4.0
2023-03-24T21:23:34.590Z
@AtmosphericPrisonEscape okay got it, thanks!
uhoh
<comets>
How commonly observed is H2 forming in H2O ice, among comets?
Mark Besser
# How commonly observed is H2 forming in H2O ice, among comets?

(Asked by: username_0 on 2023-03-23)

How common is H2 forming under a shell of normal ice, among comets?

The context is the Oumuamua discussion, and its latest tentative solution. "Acceleration of 1I/‘Oumuamua from radiolytically produced H2 in H2O ice" <https://www.nature.com/articles/s41586-022-05687-w>

Is formation of H2 in comets has discussed for long "The possible formation of a hydrogen coma around comets at large heliocentric distances" <https://ui.adsabs.harvard.edu/abs/1988ApJ...324L..31B/abstract>

...but has it been observed before? Or is Oumuamua perhaps its first observation?

**Tags:** comets
> **Comments:**
> **username_1**: It's never been observed, that's the problem. Hydrogen is invisible at temperature below several thousand K.  
> **username_1**: Do you have access to the text of the nature article? Their first three paragraphs outline how a) H2 is non-detectable in the wavelengths that were observed and b) gives a list of laboratory experiments that show H2 production in porous H2O ices in lab settings.  
> **username_2**: @AtmosphericPrisonEscape "Hydrogen is invisible at temperature below several thousand K." Maybe in visible, but what about far infrared and radio?  
> **username_0**: @AtmosphericPrisonEscape  Unfortunately not, but their datasets are open "The datasets generated and analysed during the current study are available on GitHub at https://github.com/bergnerjb/Oumuamua_H2."  
> **username_1**: @MarkBesser The data they are analysing there, are the trajectories of the object under the presumed hydrogen outgassing, which they model using the code Mercury. The data generated and available is that simulation data. So those are not experimental datasets. You could try "other sources" on the internet *cough* to get your hands on this article...  
> **username_1**: @uhoh Quadrupole and spin-transitions are way too faint to measure $H_2$ outgassing from comets, they are even too faint to measure protoplanetary disc masses.  
> **username_2**: @AtmosphericPrisonEscape okay got it, thanks!  

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