Abstract

While the structural complexity of cometary comae is already recognizable from telescopic observations1, the innermost region, within a few radii of the nucleus, was not resolved until spacecraft exploration became a reality2,3. The dust coma displays jet-like features of enhanced brightness superposed on a diffuse background1,4,5. Some features can be traced to specific areas on the nucleus, and result conceivably from locally enhanced outgassing and/or dust emission6,7,8. However, diffuse or even uniform activity over topographic concavity can converge to produce jet-like features9,10. Therefore, linking observed coma morphology to the distribution of activity on the nucleus is difficult11,12. Here, we study the emergence of dust activity at sunrise on comet 67P/Churyumov–Gerasimenko using high-resolution, stereo images from the OSIRIS camera onboard the Rosetta spacecraft, where the sources and formation of the jet-like features are resolved. We perform numerical simulations to show that the ambient dust coma is driven by pervasive but non-uniform water outgassing from the homogeneous surface layer. Physical collimations of gas and dust flows occur at local maxima of insolation and also via topographic focusing. Coma structures are projected to exhibit jet-like features that vary with the perspective of the observer. For an irregular comet such as 67P/Churyumov–Gerasimenko, near-nucleus coma structures can be concealed in the shadow of the nucleus, which further complicates the picture.

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Acknowledgements

OSIRIS was built by a consortium led by the Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany, in collaboration with CISAS, University of Padova, Italy, the Laboratoire d’Astrophysique de Marseille, France, the Instituto de Astrofísica de Andalucia, CSIC, Granada, Spain, the Scientific Support Office of the European Space Agency, Noordwijk, The Netherlands, the Instituto Nacional de Técnica Aeroespacial, Madrid, Spain, the Universidad Politéchnica de Madrid, Spain, the Department of Physics and Astronomy of Uppsala University, Sweden, and the Institut für Datentechnik und Kommunikationsnetze der Technischen Universität Braunschweig, Germany. The support of the national funding agencies of Germany (DLR), France (CNES), Italy (ASI), Spain (MEC), Sweden (SNSB) and the ESA Technical Directorate is gratefully acknowledged.

Author information

Affiliations

  1. Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany

    • X. Shi
    • , X. Hu
    • , H. Sierks
    • , C. Güttler
    • , J. Agarwal
    • , C. Tubiana
    • , S. Boudreault
    • , J. Deller
    • , G. Kovacs
    •  & J.-R. Kramm
  2. Institut für Geophysik und extraterrestrische Physik (IGEP), Technische Universität Braunschweig, Braunschweig, Germany

    • X. Hu
    •  & H. U. Keller
  3. Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut für Planetenforschung, Asteroiden und Kometen, Berlin, Germany

    • S. Mottola
    • , H. U. Keller
    • , S. F. Hviid
    • , J. Knollenberg
    • , E. Kührt
    • , N. Oklay
    •  & J.-B. Vincent
  4. PI-DSMC, Sindelfingen, Germany

    • M. Rose
  5. INAF - Osservatorio Astronomico, Trieste, Italy

    • M. Fulle
  6. LESIA, Observatoire de Paris, PSL Research University, CNRS, Univ. Paris Diderot, Sorbonne Paris Cité, UPMC Univ. Paris 06, Sorbonne Universités, Meudon Principal Cedex, France

    • S. Fornasier
    •  & M. A. Barucci
  7. NASA Ames Research Center, Moffett Field, CA, USA

    • M. Pajola
  8. Department of Astronomy, University of Maryland, College Park, MD, USA

    • D. Bodewits
  9. Department of Physics and Astronomy, University of Padova, Padova, Italy

    • C. Barbieri
    • , I. Bertini
    • , M. Lazzarin
    •  & F. Marzari
  10. Laboratoire Atmosphères, Milieux et Observations Spatiales, CNRS & Université de Versailles Saint-Quentin-en-Yvelines, Guyancourt, France

    • P. L. Lamy
    •  & J.-L. Bertaux
  11. Centro de Astrobiologia, CSIC-INTA, Madrid, Spain

    • R. Rodrigo
  12. International Space Science Institute, Bern, Switzerland

    • R. Rodrigo
  13. Scientific Support Office, European Space Research and Technology Centre/ESA, Noordwijk ZH, The Netherlands

    • D. Koschny
  14. INAF, Osservatorio Astronomico di Padova, Padova, Italy

    • G. Cremonese
  15. CNR-IFN UOS Padova LUXOR, Padova, Italy

    • V. Da Deppo
    •  & G. Naletto
  16. Jet Propulsion Laboratory, Pasadena, CA, USA

    • B. Davidsson
  17. Department of Industrial Engineering, University of Padova, Padova, Italy

    • S. Debei
  18. University of Trento, Faculty of Engineering, Trento, Italy

    • M. De Cecco
  19. Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, Marseille, France

    • O. Groussin
    •  & L. Jorda
  20. Instituto de Astrofísica de Andalucía -CSIC, Glorieta de la Astronomia, Granada, Spain

    • P. J. Gutiérrez
    • , L. M. Lara
    •  & J. J. Lopez-Moreno
  21. Graduate Institute of Astronomy, National Central University, Chung-Li, Taiwan

    • W.-H. Ip
  22. Operations Department, European Space Astronomy Centre/ESA, Villanueva de la Cañada (Madrid), Spain

    • M. Küppers
  23. Department of Physics and Astronomy “G. Galilei”, University of Padova, Padova, Italy

    • G. Naletto
  24. Center of Studies and Activities for Space, CISAS, ‘G. Colombo’, University of Padova, Padova, Italy

    • G. Naletto
  25. MTA CSFK Konkoly Observatory, Budapest, Hungary

    • I. Toth

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Contributions

X.S. led this study, analysed imaging data, performed simulations for gas and dust field modelling, and drafted the manuscript. X.H. contributed to design of the study, performed part of the thermo-physical analysis and contributed to drafting the manuscript. S.M. contributed to the thermo-physical modelling of water activity along dawn terminator and contributed to improving the manuscript. M.R. carried out the development and modification of DSMC code used for cometary coma modelling. H.U.K. and M.F. contributed to interpretation of the results. H.S., C.G. and C.T. participated in early discussions of the study and helped improve the manuscript. S.F., M.P., J.A. and D.B. contributed to improving the manuscript. All remaining authors contributed to the construction, operation and calibration of OSIRIS cameras, which ensured the acquirement of high-quality data used for this study.

Competing interests

The authors declare no competing interests.

Corresponding author

Correspondence to X. Shi.

Supplementary information

  1. Supplementary Information

    Supplementary Figures 1–5, Supplementary Table 1, Supplementary Video 1 caption.

  2. Supplementary Video 1

    Trajectories of dust particles emitting from the Hapi region observed from a continuously changing perspective.

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DOI

https://doi.org/10.1038/s41550-018-0481-5