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.

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    $\begingroup$ Are you talking about terrestrial ("small") exoplanets? Because giant exoplanets surely can keep their hydrogen. $\endgroup$ Aug 25 at 11:58
  • $\begingroup$ 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. $\endgroup$
    – notovny
    Aug 25 at 12:12
  • $\begingroup$ @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) $\endgroup$ Aug 25 at 13:56
  • $\begingroup$ @NilayGhosh Europa also has mostly oxygen "atmosphere", but neither Mercury nor Europa has proper atmosphere though. $\endgroup$
    – Anixx
    Aug 25 at 14:57
  • $\begingroup$ 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. $\endgroup$
    – antlersoft
    Aug 25 at 14:59


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