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Dual storage and release of molecular oxygen in comet 67P/Churyumov–Gerasimenko

Abstract

One of the biggest surprises of the Rosetta mission was the detection of O2 in the coma of 67P/Churyumov–Gerasimenko in remarkably high abundances. The measured levels of O2 in the coma are generally assumed to reflect the overall abundance and chemical origin of cometary O2 in the nucleus. Along with its strong association with H2O and weak association with CO and CO2, these measurements led to the consensus that the source and release of cometary O2 are linked to H2O. We analysed ROSINA observations and found a previously unrecognized change in the correlations of O2 with H2O, CO2 and CO that contradicts the prevailing notion that the release of O2 is linked to H2O at all times. These findings can be explained by the presence of two distinct reservoirs of O2: a pristine source in the deeper nucleus layers dating back to before nucleus formation, and an H2O-trapped secondary reservoir formed during the thermal evolution of the nucleus. These results imply that O2 must have been incorporated into the nucleus in a solid and distinct phase during accretion in significantly lower abundances than previously assumed.

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Fig. 1: Correlations of O2 with the major species before the pre-perihelion equinox.
Fig. 2: Correlations of O2 with the major species after the post-perihelion equinox.
Fig. 3: O2 correlations with the major cometary volatile species during low H2O production.
Fig. 4: O2 trapping in and release from the two distinct nucleus reservoirs.

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Data availability

All data processed as described above are included in the Article and Supplementary Information. The ROSINA/DFMS spectra used to derive count rates are available in the NASA Planetary DataSystem (https://pds-smallbodies.astro.umd.edu/data_sb/missions/rosetta/index.shtml) and ESA Planetary Science Archive (https://archives.esac.esa.int/psa/#!Table%20View/Rosetta=mission). Source data are provided with this paper.

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Acknowledgements

This work was supported by the National Aeronautics and Space Administration (NASA) through grant number 80NSSC18K1620 (A.L.-K., S.A.F., K.E.M., K.J.T. and S.M.P.), the Excellence Initiative of Aix-Marseille Université–A*Midex, a French ‘Investissements d’Avenir programme’ AMX-21-IET-018 and CNES (O.M.), NASA grant number NNX17AL71A (J.I.L.) and CNRS-INSU national programmes PCMI and PNP (F.P., Y.E. and O.O.).

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Authors and Affiliations

Authors

Contributions

A.L.-K. conceptualized and led the study, performed the data analysis, interpreted the results and wrote the manuscript. O.M. contributed to the conceptualization and methodology of gas trapping, and the implications of the results for cometary origin. F.P., Y.E. and O.O. performed the chemical modelling of gas trapping in H2O ice and assisted in the interpretation. J.l.L. contributed to the interpretation of the results and to the chemistry of ice trapping. S.A.F. supported all steps of the data analysis and assisted in the correlation study. K.E.M. contributed to the data analysis and interpretation. K.J.T. and S.M.P. developed the fitting routine, performed the spectral fits to the ROSINA/DFMS mass spectra and provided the time-series files of the count rates of the analysed species. All authors contributed to the discussion of the results, interpretation and writing of the manuscript.

Corresponding author

Correspondence to Adrienn Luspay-Kuti.

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Nature Astronomy thanks Dennis Bodewits, Michael Disanti and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Fig. 1, Tables 1 and 2 and discussion of data treatment.

Source data

Source Data Fig. 1

Statistical source data.

Source Data Fig. 2

Statistical source data.

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Statistical source data.

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Luspay-Kuti, A., Mousis, O., Pauzat, F. et al. Dual storage and release of molecular oxygen in comet 67P/Churyumov–Gerasimenko. Nat Astron 6, 724–730 (2022). https://doi.org/10.1038/s41550-022-01614-1

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