Organohalogens, a class of molecules that contain at least one halogen atom bonded to carbon, are abundant on the Earth where they are mainly produced through industrial and biological processes1. Consequently, they have been proposed as biomarkers in the search for life on exoplanets2. Simple halogen hydrides have been detected in interstellar sources and in comets, but the presence and possible incorporation of more complex halogen-containing molecules such as organohalogens into planet-forming regions is uncertain3,4. Here we report the interstellar detection of two isotopologues of the organohalogen CH3Cl and put some constraints on CH3F in the gas surrounding the low-mass protostar IRAS 16293–2422, using the Atacama Large Millimeter/submillimeter Array (ALMA). We also find CH3Cl in the coma of comet 67P/Churyumov–Gerasimenko (67P/C-G) by using the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) instrument. The detections reveal an efficient pre-planetary formation pathway of organohalogens. Cometary impacts may deliver these species to young planets and should thus be included as a potential abiotical production source when interpreting future organohalogen detections in atmospheres of rocky planets.

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This work is based on observations from ALMA, a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of Korea), in co-operation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. Data from ROSINA, an instrument part of Rosetta mission, were used in this work. Rosetta is a European Space Agency (ESA) mission with contributions from its member states and NASA, and we acknowledge herewith the work of the whole ESA Rosetta team. E.C.F. and K.I.O. acknowledge financial support from the Simons Foundation (SCOL award 321183, KO) and to Northrop Grumman Corporation. The group of J.K.J. acknowledges support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 646908) through ERC Consolidator Grant S4F. Research at the Centre for Star and Planet Formation is funded by the Danish National Research Foundation. Work at the University of Bern was funded by the State of Bern, the Swiss National Science Foundation, and the ESA PRODEX programme (Programme de Développement d’Expériences scientifiques). E.F.v.D. acknowledges A-ERC grant CHEMPLAN 291141. M.N.D. acknowledges the financial support of the Center for Space and Habitability (CSH) Fellowship and the IAU Gruber Foundation Fellowship. S.F.W. acknowledges financial support from a CSH fellowship.

Author information


  1. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, 02138, USA

    • Edith C. Fayolle
    •  & Karin I. Öberg
  2. Centre for Star and Planet Formation, Niels Bohr Institute and Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5–7, DK-1350, Copenhagen K, Denmark

    • Jes K. Jørgensen
    •  & Hannah Calcutt
  3. Physikalisches Institut, University of Bern, Sidlerstrasse 5, CH-3012, Bern, Switzerland

    • Kathrin Altwegg
    •  & Martin Rubin
  4. Center for Space and Habitability, University of Bern, Sidlerstrasse 5, CH-3012, Bern, Switzerland

    • Kathrin Altwegg
    • , Maria N. Drozdovskaya
    •  & Susanne F. Wampfler
  5. I. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937, Köln, Germany

    • Holger S. P. Müller
  6. ASTRON, the Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA, Dwingeloo, The Netherlands

    • Matthijs H. D. van der Wiel
  7. Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, 439 92, Onsala, Sweden

    • Per Bjerkeli
    •  & Magnus V. Persson
  8. SKA Organization, Jodrell Bank Observatory, Lower Withington, Macclesfield, SK11 9DL, UK

    • Tyler L. Bourke
  9. Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, UK

    • Audrey Coutens
  10. Leiden Observatory, Leiden University, PO Box 9513, 2300 RA, Leiden, The Netherlands

    • Ewine F. van Dishoeck
    •  & Niels F. W. Ligterink
  11. Max-Planck Institut für Extraterrestrische Physik (MPE), Giessenbachstr. 1, 85748, Garching, Germany

    • Ewine F. van Dishoeck
  12. Departments of Chemistry and Astronomy, University of Virginia, Charlottesville, VA, 22904, USA

    • Robin T. Garrod
  13. Raymond and Beverly Sackler Laboratory for Astrophysics, Leiden Observatory, Leiden University, PO Box 9513, 2300 RA, Leiden, The Netherlands

    • Niels F. W. Ligterink
  14. Physikalisches Institut, University of Bern, Sidlerstrasse 5, CH-3012, Bern, Switzerland

    • H. Balsiger
    • , S. Gasc
    • , T. Sémon
    •  & C. -Y. Tzou
  15. LATMOS 4 Avenue de Neptune, F-94100, SAINT-MAUR, France

    • J. J. Berthelier
  16. Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Ringlaan 3, B-1180, Brussels, Belgium

    • J. De Keyser
  17. Institute of Computer and Network Engineering (IDA), TU Braunschweig, Hans-Sommer-Strasse 66, D-38106, Braunschweig, Germany

    • B. Fiethe
  18. Space Science Division, Southwest Research Institute, 6220 Culebra Road, San Antonio, TX, 78228, USA

    • S. A. Fuselier
  19. Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, 2455 Hayward, Ann Arbor, MI, 48109, USA

    • T. I. Gombosi


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  1. the ROSINA team


E.C.F. initiated the project, and identified and analysed the newly detected species in the protostar spectra. E.C.F. and K.I.O. wrote the manuscript together. The Principal Investigator of the PILS survey, J.K.J, together with H.C. and M.H.D.v.d.W. generated the datacubes from the ALMA observations and assisted with the column density determinations. H.S.P.M. computed the CH3F line catalogue and assisted with the CH3Cl spectroscopy interpretations. R.T.G contributed the text on the formation pathways to organohalogens under interstellar medium conditions. The Principal Investigator of the ROSINA programme, K.A., together with M.R. reduced the DFMS data, and identified and provided the CH3Cl abundance ratios. The ALMA-PILS and ROSINA-DFMS collaboration was initiated by E.F.v.D., M.N.D. and S.F.W. J.K.J., H.S.P.M. and E.F.v.D. provided extensive input on the text. All the authors contributed to discussions of the results and commented on the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Edith C. Fayolle.

Electronic supplementary material

  1. Supplementary Information

    Supplementary Text and Supplementary References.