A mini outburst from the nightside of comet 67P/Churyumov-Gerasimenko observed by the OSIRIS camera on Rosetta

Joerg Knollenberg (1) , Z. Y. Lin (2) , S. F. Hviid (1) , N. Oklay (3) , J.-B. Vincent (3) , Dennis Bodewits (4) , S. Mottola (1) , M. Pajola (5) , H. Sierks (3) , C. Barbieri (6) , Philippe Lamy (7) , R. Rodrigo (8, 9) , D. Koschny (10) , H. Rickman (11, 12) , Michael F. A'Hearn (4) , M. A. Barucci (13) , Jean-Loup Bertaux (14) , I. Bertini (5) , Gabriele Cremonese (6) , B. Davidsson (12) , V. da Deppo (15) , S. Debei (16) , M. de Cecco (17) , S. Fornasier (13) , M. Fulle (18) , O. Groussin (7) , Pedro J. Gutiérrez (19) , W.-H. Ip (2) , L. Jorda (7) , H. U. Keller (20, 1) , Ekkehard Kührt (1) , J. R. Kramm (3) , M. Küppers (21) , L. M. Lara (19) , M. Lazzarin (6) , J. J. Lopez Moreno (19) , F. Marzari (6) , G. Naletto (22, 5, 15) , N. Thomas (23) , C. Güttler (3) , F. Preusker (1) , F. Scholten (1) , C. Tubiana (3)

1 DLR Institut für Planetenforschung
2 Institute of Space Science [Taiwan]
3 MPS - Max-Planck-Institut für Sonnensystemforschung
4 Department of Astronomy [College Park]
5 CISAS - Centro di Ateneo di Studi e Attività Spaziali “Giuseppe Colombo”
6 Dipartimento di Fisica e Astronomia "Galileo Galilei"
7 LAM - Laboratoire d'Astrophysique de Marseille
8 CAB - Centro de Astrobiologia [Madrid]
9 ISSI - International Space Science Institute [Bern]
10 ESTEC - European Space Research and Technology Centre
11 CBK - Space Research Centre of Polish Academy of Sciences
12 Department of Physics and Astronomy [Uppsala]
13 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
14 PLANETO - LATMOS
15 IFN - CNR Institute for Photonics and Nanotechnologies
16 Department of Industrial Engineering [Padova]
17 UNITN - Università degli Studi di Trento
18 OAT - INAF - Osservatorio Astronomico di Trieste
19 IAA - Instituto de Astrofísica de Andalucía
20 IGEP - Institut für Geophysik und Extraterrestrische Physik [Braunschweig]
21 Operations Department (ESAC)
22 DEI - Department of Information Engineering [Padova]
23 Physikalisches Institut [Bern]

On 12 March 2015 the OSIRIS WAC camera onboard the ESA Rosetta spacecraft orbiting comet 67P/Churyumov-Gerasimenko observed a small outburst originating from the Imhotep region at the foot of the big lobe of the comet. These measurements are unique since it was the first time that the initial phase of a transient outburst event could be directly observed. Aims. We investigate the evolution of the dust jet in order to derive clues about the outburst source mechanism and the ejected dust particles, in particular the dust mass, dust-to-gas ratio and the particle size distribution. Methods. Analysis of the images and of the observation geometry using comet shape models in combination with gasdynamic modeling of the transient dust jet were the main tools used in this study. Synthetic images were computed for comparison with the observations. Results. Analysis of the geometry revealed that the source region was not illuminated until 1.5 h after the event implying true nightside activity was observed. The outburst lasted for less than one hour and the average dust production rate during the initial four minutes was of the order of 1 kg/s. During this time the outburst dust production rate was approximately constant, no sign for an initial explosion could be detected. For dust grains between 0.01-1 mm a power law size distribution characterized by an index of about 2.6 provides the best fit to the observed radiance profiles. The dust-to-gas ratio of the outburst jet is in the range 0.6-1.8.

Domains: Earth and Planetary Astrophysics [astro-ph.EP]

Joerg Knollenberg, Z. Y. Lin, S. F. Hviid, N. Oklay, J.-B. Vincent, et al.. A mini outburst from the nightside of comet 67P/Churyumov-Gerasimenko observed by the OSIRIS camera on Rosetta. Astronomy and Astrophysics - A&A, 2016, 596, A89 (10 p.). ⟨10.1051/0004-6361/201527744⟩. ⟨insu-01371309⟩