D2O and HDS in the coma of 67P/Churyumov-Gerasimenko

K Altwegg; H Balsiger; J J Berthelier; A Bieler; U Calmonte; J De Keyser; B Fiethe; S A Fuselier; S Gasc; T I Gombosi; T Owen; L Le Roy; M Rubin; T Sémon; C-Y Tzou

doi:10.1098/rsta.2016.0253

D₂O and HDS in the coma of 67P/Churyumov-Gerasimenko

Philos Trans A Math Phys Eng Sci. 2017 Jul 13;375(2097):20160253. doi: 10.1098/rsta.2016.0253.

Authors

K Altwegg^{1

2}, H Balsiger³, J J Berthelier⁴, A Bieler^{3

5}, U Calmonte³, J De Keyser⁶, B Fiethe⁷, S A Fuselier⁸, S Gasc³, T I Gombosi⁴, T Owen⁹, L Le Roy³, M Rubin³, T Sémon³, C-Y Tzou³

Affiliations

¹ Physikalisches Institut, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland kathrin.altwegg@space.unibe.ch.
² Center for Space and Habitability, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland.
³ Physikalisches Institut, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland.
⁴ LATMOS 4 Avenue de Neptune, 94100 Saint-Maur, France.
⁵ Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, 2455 Hayward, Ann Arbor, MI 48109, USA.
⁶ Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Ringlaan 3, 1180 Brussels, Belgium.
⁷ Institute of Computer and Network Engineering (IDA), TU Braunschweig, Hans-Sommer-Strasse 66, 38106 Braunschweig, Germany.
⁸ Space Science Division, Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78228, USA.
⁹ Institute for Astronomy, University of Hawaii, Honolulu, HI 96822, USA.

Abstract

The European Rosetta mission has been following comet 67P/Churyumov-Gerasimenko for 2 years, studying the nucleus and coma in great detail. For most of these 2 years the Rosetta Orbiter Sensor for Ion and Neutral Analysis (ROSINA) has analysed the volatile part of the coma. With its high mass resolution and sensitivity it was able to not only detect deuterated water HDO, but also doubly deuterated water, D₂O and deuterated hydrogen sulfide HDS. The ratios for [HDO]/[H₂O], [D₂O]/[HDO] and [HDS]/[H₂S] derived from our measurements are (1.05 ± 0.14) × 10^-3, (1.80 ± 0.9) × 10^-2 and (1.2 ± 0.3) × 10^-3, respectively. These results yield a very high ratio of 17 for [D₂O]/[HDO] relative to [HDO]/[H₂O]. Statistically one would expect just 1/4. Such a high value can be explained by cometary water coming unprocessed from the presolar cloud, where water is formed on grains, leading to high deuterium fractionation. The high [HDS]/[H₂S] ratio is compatible with upper limits determined in low-mass star-forming regions and also points to a direct correlation of cometary H₂S with presolar grain surface chemistry.This article is part of the themed issue 'Cometary science after Rosetta'.

Keywords: 67P/Churyumov–Gerasimenko; Rosetta; comets; deuterium.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.
Research Support, Non-U.S. Gov't