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Published May 8, 2017 | Published + Supplemental Material
Journal Article Open

Dynamic molecular oxygen production in cometary comae


Abundant molecular oxygen was discovered in the coma of comet 67P/Churyumov–Gerasimenko. Its origin was ascribed to primordial gaseous O₂ incorporated into the nucleus during the comet's formation. This thesis was put forward after discounting several O₂ production mechanisms in comets, including photolysis and radiolysis of water, solar wind–surface interactions and gas-phase collisions. Here we report an original Eley–Rideal reaction mechanism, which permits direct O₂ formation in single collisions of energetic water ions with oxidized cometary surface analogues. The reaction proceeds by H₂O+ abstracting a surface O-atom, then forming an excited precursor state, which dissociates to produce O₂−. Subsequent photo-detachment leads to molecular O₂, whose presence in the coma may thus be linked directly to water molecules and their interaction with the solar wind. This abiotic O₂ production mechanism is consistent with reported trends in the 67P coma and raises awareness of the role of energetic negative ions in comets.

Additional Information

© 2017 The Author(s). This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. Received: 18 November 2016; Accepted: 07 March 2017; Published online: 08 May 2017. This report was based on work funded by the National Science Foundation/Department of Energy Partnership for Basic Plasma Science and Engineering (Award No. 1202567). Author Contributions: Y.Y. and K.P.G. designed the experiments and co-wrote the paper. Y.Y. conducted experimental measurements. K.P.G. supervised the project. The authors declare no competing financial interests.

Attached Files

Published - ncomms15298.pdf

Supplemental Material - ncomms15298-s1.pdf

Supplemental Material - ncomms15298-s2.pdf


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