Sulphur-bearing species in the coma of comet 67P/Churyumov–Gerasimenko

Ursina Calmonte (1) , Kathrin Altwegg (2, 1) , Hans Balsiger (1) , Jean-Jacques Berthelier (3) , A. Bieler (4, 1) , G. Cessateur (5) , F. Dhooghe (5) , E. F. van Dishoeck (6) , B. Fiethe (7) , S. Fuselier (8) , S. Gasc (1) , Tamas I. Gombosi (4) , M. Hässig (1, 8) , Léna Le Roy (1) , Martin Rubin (1) , T. Sémon (1) , C.-Y. Tzou (1) , S. F. Wampfler (2)

1 Physikalisches Institut [Bern]
2 CSH - Center for Space and Habitability
3 PLANETO - LATMOS
4 CLaSP - Department of Climate and Space Sciences and Engineering
5 BIRA-IASB - Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique
6 Leiden Observatory [Leiden]
7 IDA - Institute of Computer and Network Engineering [Braunschweig]
8 Space Science Division [San Antonio]

Several sulphur-bearing species have already been observed in different families of comets. However, the knowledge on the minor sulphur species is still limited. The comet's sulphur inventory is closely linked to the pre-solar cloud and holds important clues to the degree of reprocessing of the material in the solar nebula and during comet accretion. Sulphur in pre-solar clouds is highly depleted, which is quite puzzling as the S/O ratio in the diffuse interstellar medium is cosmic. This work focuses on the abundance of the previously known species H₂S, OCS, SO, S₂, SO₂ and CS₂ in the coma of comet 67P/Churyumov–Gerasimenko measured by Rosetta Orbiter Spectrometer for Ion and Neutral Analysis/Double Focusing Mass Spectrometer between equinox and perihelion 2015. Furthermore, we present the first detection of S₃, S₄, CH₃SH and C₂H₆S in a comet, and we determine the elemental abundance of S/O in the bulk ice of (1.47 ± 0.05) × 10⁻². We show that SO is present in the coma originating from the nucleus, but not CS in the case of 67P, and for the first time establish that S₂ is present in a volatile and a refractory phase. The derived total elemental sulphur abundance of 67P is in agreement with solar photospheric elemental abundances and shows no sulphur depletion as reported for dense interstellar clouds. Also the presence of S₂ at heliocentric distances larger than 3 au indicates that sulphur-bearing species have been processed by radiolysis in the pre-solar cloud and that at least some of the ice from this cloud has survived in comets up the present.

Mots clés: space vehicles; comets; 67P/Churyumov–Gerasimenko

Domaines: Astrophysique [astro-ph]

Ursina Calmonte, Kathrin Altwegg, Hans Balsiger, Jean-Jacques Berthelier, A. Bieler, et al.. Sulphur-bearing species in the coma of comet 67P/Churyumov–Gerasimenko. Monthly Notices of the Royal Astronomical Society, 2016, 462 (Suppl 1), pp.S253 - S273. ⟨10.1093/mnras/stw2601⟩. ⟨insu-01402761⟩