Evidence for distributed gas sources of hydrogen halides in the coma of comet 67P/Churyumov-Gerasimenko

De Keyser, Johan; Dhooghe, Frederik; Altwegg, Kathrin; Balsiger, Hans; Berthelier, Jean-Jacques; Briois, Christelle; Calmonte, Ursina Maria; Cessateur, Gaël; Combi, Michael R.; Equeter, Eddy; Fiethe, Björn; Fuselier, Stephen; Gasc, Sébastien; Gibbons, Andrew; Gombosi, Tamas; Gunell, Herbert; Hässig, Myrtha; Le Roy, Léna; Maggiolo, Romain; Mall, Urs; ... (2017). Evidence for distributed gas sources of hydrogen halides in the coma of comet 67P/Churyumov-Gerasimenko. Monthly notices of the Royal Astronomical Society, 469(Suppl_2), S695-S711. Oxford University Press 10.1093/mnras/stx2725

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Rosetta has detected the presence of the hydrogen halides HF, HCl, and HBr in the coma of comet 67P/Churyumov-Gerasimenko. These species are known to freeze out on icy grains in molecular clouds. Analysis of the abundances of HF and HCl as a function of cometocentric distance suggests that these hydrogen halides are released both from the nucleus surface and off dust particles in the inner coma. We present three lines of evidence. First, the abundances of HF and HCl relative to the overall neutral gas in the coma appear to increase with distance, indicating that a net source must be present; since there is no hint at any possible parent species with suffcient abundances that could explain the observed levels of HF or HCl, dust particles are the likely origin. Second, the
amplitude of the daily modulation of the halide-to-water density due to the rotation and geometry of 67P's nucleus and the corresponding surface illumination is observed to progressively diminish with distance and comet dust activity; this can be understood from the range of dust particle speeds well below the neutral gas expansion speed, which tends to smooth the coma density proffles. Third, strong halogen abundance changes detected locally in the coma cannot be easily explained from composition changes at the surface, while they can be understood from differences in local gas production from the dust particles.

Item Type:

Journal Article (Original Article)


08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
08 Faculty of Science > Other Institutions > Emeriti, Faculty of Science
08 Faculty of Science > Physics Institute
10 Strategic Research Centers > Center for Space and Habitability (CSH)

UniBE Contributor:

Altwegg, Kathrin; Balsiger, Hans; Calmonte, Ursina Maria; Gasc, Sébastien; Le Roy, Léna; Rubin, Martin; Sémon, Thierry; Tzou, Chia-Yu and Wurz, Peter


500 Science > 520 Astronomy
600 Technology > 620 Engineering
500 Science > 530 Physics




Oxford University Press




Dora Ursula Zimmerer

Date Deposited:

14 Nov 2017 11:09

Last Modified:

29 Nov 2017 01:32

Publisher DOI:






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