<p>Has been there detected any exoplanets with significant share of oxygen in atmosphere? What does the theory predict?</p>
<p>Superficially this looks like it should be fairly common: there is a lot of water in the universe and hydrogen can easily escape most medium-sized bodies leaving oxygen behind.</p>

CC BY-SA 4.0
2023-08-25T11:58:32.037Z
Are you talking about terrestrial ("small") exoplanets? Because giant exoplanets surely can keep their hydrogen.
AtmosphericPrisonEscape
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2023-08-25T12:12:16.013Z
Molecular oxygen doesn't generally hang around planets long term, unless there's some sort of unusual self-sustaining chemical process constantly generating huge amounts of it for some reason. It usually binds up in other compounds, such as water vapor  or carbon dioxide in atmospheres.
notovny
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2023-08-25T13:56:22.217Z
@AtmosphericPrisonEscape I deleted my answer upon checking your comment. Indeed OP is looking for exoplanets with oxygen dominant atmosphere. It is unlikely there in one. Most of then are hydrogen dominant. If we talk about our solar system, [turns out mercury's atmosphere is 42% oxygen (the only planet with oxygen as dominant species and only other planet to have oxygen apart from Earth)](https://www.nasa.gov/sites/default/files/files/YOSS_Act_4.pdf)
Nilay Ghosh
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2023-08-25T14:57:04.480Z
@NilayGhosh Europa also has mostly oxygen "atmosphere", but neither Mercury nor Europa has proper atmosphere though.
Anixx
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2023-08-25T14:59:47.833Z
I would think theory would predict that *thus far* we wouldn't have found *any* exoplanets with oxygen-rich atmosphere, since the only exoplanet atmospheres we can analyze with current instruments are found on hot gas giants.
antlersoft
<exoplanet><planetary-atmosphere>
How common are there planets with significant share of oxygen in atmosphere?
Anixx
# How common are there planets with significant share of oxygen in atmosphere?

(Asked by: username_0 on 2023-08-25)

Has been there detected any exoplanets with significant share of oxygen in atmosphere? What does the theory predict?

Superficially this looks like it should be fairly common: there is a lot of water in the universe and hydrogen can easily escape most medium-sized bodies leaving oxygen behind.

**Tags:** exoplanet, planetary-atmosphere
> **Comments:**
> **username_1**: Are you talking about terrestrial ("small") exoplanets? Because giant exoplanets surely can keep their hydrogen.  
> **username_2**: Molecular oxygen doesn't generally hang around planets long term, unless there's some sort of unusual self-sustaining chemical process constantly generating huge amounts of it for some reason. It usually binds up in other compounds, such as water vapor  or carbon dioxide in atmospheres.  
> **username_3**: @AtmosphericPrisonEscape I deleted my answer upon checking your comment. Indeed OP is looking for exoplanets with oxygen dominant atmosphere. It is unlikely there in one. Most of then are hydrogen dominant. If we talk about our solar system, [turns out mercury's atmosphere is 42% oxygen (the only planet with oxygen as dominant species and only other planet to have oxygen apart from Earth)](https://www.nasa.gov/sites/default/files/files/YOSS_Act_4.pdf)  
> **username_0**: @NilayGhosh Europa also has mostly oxygen "atmosphere", but neither Mercury nor Europa has proper atmosphere though.  
> **username_4**: I would think theory would predict that *thus far* we wouldn't have found *any* exoplanets with oxygen-rich atmosphere, since the only exoplanet atmospheres we can analyze with current instruments are found on hot gas giants.  

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