Are fractured cliffs the source of cometary dust jets? Insights from OSIRIS/Rosetta at 67P/Churyumov-Gerasimenko

¹ Max-Planck Institut fuer Sonnensystemforschung, Justus-von-Liebig-Weg, 3, 37077 Goettingen, Germany
e-mail: vincent@mps.mpg.de
² Centro di Ateneo di Studi ed Attivitá Spaziali “Giuseppe Colombo” (CISAS), University of Padova, via Venezia 15, 35131 Padova, Italy
³ Institute for Geophysics and Extraterrestrial Physics, TU Braunschweig, 38106 Braunschweig, Germany
⁴ Department of Physics and Astronomy “G. Galilei”, University of Padova, Vic. Osservatorio 3, 35122 Padova, Italy
⁵ Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astro-physique de Marseille) UMR 7326, 13388 Marseille, France
⁶ Centro de Astrobiologia (INTA-CSIC), European Space Agency (ESA), European Space Astronomy Centre (ESAC), PO Box 78, 28691 Villanueva de la Canada, Madrid, Spain
⁷ International Space Science Institute, Hallerstrasse 6, 3012 Bern, Switzerland
⁸ Research and Scientific Support Department, European Space Agency, 2201 Noordwijk, The Netherlands
⁹ Department of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden
¹⁰ PAS Space Research Center, Bartycka 18A, 00716 Warszawa, Poland
¹¹ Department for Astronomy, University of Maryland, College Park, MD 20742-2421, USA
¹² Gauss Professor Akademie der Wissenschaften zu Göttingen, 37077 Göttingen, Germany
¹³ LESIA, Observatoire de Paris, CNRS, UPMC Univ. Paris 06, Univ. Paris-Diderot, 5 place J. Janssen, 92195 Meudon Principal Cedex, France
¹⁴ LATMOS, CNRS/UVSQ/IPSL, 11 boulevard d’Alembert, 78280 Guyancourt, France
¹⁵ INAF Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
¹⁶ CNR-IFN UOS Padova LUXOR, via Trasea 7, 35131 Padova, Italy
¹⁷ Department of Industrial Engineering University of Padova via Venezia, 1, 35131 Padova, Italy
¹⁸ University of Trento, via Sommarive, 9, 38123 Trento, Italy
¹⁹ Physikalisches Institut, Sidlerstrasse 5, University of Bern, 3012 Bern, Switzerland
²⁰ INAF–Osservatorio Astronomico di Trieste, via Tiepolo 11, 34143 Trieste, Italy
²¹ Instituto de Astrofisica de Andalucia-CSIC, Glorieta de la Astronomia, 18008 Granada, Spain
²² Institute of Planetary Research, DLR, Rutherfordstrasse 2, 12489 Berlin, Germany
²³ Institute for Space Science, National Central University, 32054 Chung-Li, Taiwan
²⁴ Budapest University of Technology and Economics, Department of Mechatronics, Optics and Engineering Informatics, Muegyetem rkp 3, 1111 Budapest, Hungary
²⁵ ESA/ESAC, PO Box 78, 28691 Villanueva de la Cañada, Spain
²⁶ Centre for Astrophysics and Planetary Science, School of Physical Sciences, The University of Kent, Canterbury CT2 7NH, UK
²⁷ Department of Information Engineering, University of Padova, via Gradenigo 6/B, 35131 Padova, Italy
²⁸ Observatory of the Hungarian Academy of Sciences, PO Box 67, 1525 Budapest, Hungary

Received: 10 August 2015
Accepted: 4 December 2015

Abstract

Context. Dust jets (i.e., fuzzy collimated streams of cometary material arising from the nucleus) have been observed in situ on all comets since the Giotto mission flew by comet 1P/Halley in 1986, and yet their formation mechanism remains unknown. Several solutions have been proposed involving either specific properties of the active areas or the local topography to create and focus the gas and dust flows. While the nucleus morphology seems to be responsible for the larger features, high resolution imagery has shown that broad streams are composed of many smaller jets (a few meters wide) that connect directly to the nucleus surface.

Aims. We monitored these jets at high resolution and over several months to understand what the physical processes are that drive their formation and how this affects the surface.

Methods. Using many images of the same areas with different viewing angles, we performed a 3-dimensional reconstruction of collimated jets and linked them precisely to their sources on the nucleus.

Results. We show here observational evidence that the northern hemisphere jets of comet 67P/Churyumov-Gerasimenko arise from areas with sharp topographic changes and describe the physical processes involved. We propose a model in which active cliffs are the main source of jet-like features and therefore of the regions eroding the fastest on comets. We suggest that this is a common mechanism taking place on all comets.