Sulphur isotope mass-independent fractionation observed in comet 67P/Churyumov–Gerasimenko by Rosetta/ROSINA

Calmonte, Ursina Maria; Altwegg, K; Balsiger, Hans; Berthelier, J-J; Bieler, A; De Keyser, J; Fiethe, B; Fuselier, S A; Gasc, Sébastien; Gombosi, T I; Le Roy, Léna; Rubin, Martin; Sémon, Thierry; Tzou, Chia-Yu; Wampfler, Susanne (2017). Sulphur isotope mass-independent fractionation observed in comet 67P/Churyumov–Gerasimenko by Rosetta/ROSINA. Monthly notices of the Royal Astronomical Society, 469(Suppl_2), S787-S803. Oxford University Press 10.1093/mnras/stx2534

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The knowledge about sulphur isotopic fractionation in volatile cometary species is limited
as only measurements in five comets have been done and only for ³⁴S/³²S. The lack of
information about the fractionation of ³³/³²S makes it impossible to compare them with
what is known from refractories. We present results of ³⁴S/³²S and for the first time ³³S/³²S isotopic ratio in H₂S, OCS, and CS₂ in the coma of comet 67P/Churyumov–Gerasimenko. Observations used for this study were performed with Rosetta Orbiter Spectrometer for Ion and Neutral Analysis/Double Focusing Mass Spectrometer during 2014 October and 2016 May. Bulk isotopic ³³S/³²S and ³⁴S/³²S ratios derived from these three species yield δ³³S = (−302 ± 29)‰ and δ³⁴S = (−41 ± 17)‰, respectively. The observed isotopic fractionation is significantly different from the assumed Solar system standard [Vienna-Canyon Diablo Troilite (V-CDT)] and all other reported values for Solar system objects, except other comets. Furthermore, we show that neither mass-dependent nor mass-independent fractionation due to photodissociation as it has been observed in recent laboratory studies can be the cause of the significant depletion compared to Solar system standard. In addition, we conclude that there seems to be an intrinsic difference in sulphur isotopic fractionation in cometary volatiles and refractories while the difference between molecules is most likely due to different chemical pathways. The significant fractionation of sulphur isotopes together with a high D₂O/HDO versus HDO/H₂O and non-solar isotopic ratio for xenon as well as for Si point towards a non-homogeneously mixed protosolar nebula.

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:

Calmonte, Ursina Maria, Altwegg, Kathrin, Balsiger, Hans, Gasc, Sébastien, Le Roy, Léna, Rubin, Martin, Sémon, Thierry, Tzou, Chia-Yu, Wampfler, Susanne


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




Oxford University Press




Dora Ursula Zimmerer

Date Deposited:

18 Apr 2018 12:28

Last Modified:

02 Mar 2023 23:30

Publisher DOI:





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