Is it feasible to have an oxidizing planetary atmosphere without the presence of an organic photosynthesis of some kind on the planet?
With the emergence of cyanobacteria on earth 3.5 billion years ago, the shift from a reducing to an oxidizing atmosphere began.
"The atmospheric O$_\textrm{2}$ levels (in PAL; i.e., normalized to the present atmospheric level) would have risen mainly in two geological periods in the Earth history: the Great Oxidation Event (GOE) at 2.4"“2.0 Ga and the Neoproterozoic Oxygenation Event (NOE) at 0.8"“0.6 Ga. Overshoot of O$_\textrm{2}$ occurred at 2.2"“2.1 Ga and whiffs of O$_\textrm{2}$ occurred before the GOE. Glaciations in the Proterozoic (triangles)"”especially snowball Earth glaciations (black triangles)"”coincided with increases in the O$_\textrm{2}$ level during both GOE and NOE. Arrows with filled and open circles and bars are constraints from geochemical studies (e.g., Farquhar et al. 2007; Goto et al. 2013; Klemm 2000 ; Pavlov and Kasting 2002)."[1]
Would a non-organic based and/or non-photosynthetic derived oxidizing atmosphere be feasible on a planetary scale?
If so, given that the earth's oxidizing atmosphere is derived from the sun's thermonuclear energy over billions of years, what would be the ultimate source of energy for such a non-organic based and/or non-photosynthetic derived oxidizing atmosphere?
 [1] Tajika, Eiichi, and Mariko Harada. "Great Oxidation Event and Snowball Earth." Astrobiology, 28 Feb. 2019, pp. 261"“271, https://link.springer.com/chapter/10.1007%2F978-981-13-3639-3_17.
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