Seasonal Mass Transfer on the Nucleus of Comet 67P/Chuyumov-Gerasimenko

Horst Uwe Keller (1, 2) , Stefano Mottola (1) , Stubbe F. Hviid (1) , Jessica Agarwal (3) , Ekkehard Kührt (1) , Yuri Skorov (2) , Katharina Otto (1) , Jean-Baptiste Vincent (1) , Nilda Oklay (1) , Stephan E. Schröder (1) , Björn Davidsson (4) , Maurizio Pajola (5, 6) , Xian Shi (3) , Dennis Bodewits (7) , Imre Toth (8) , Frank Preusker (1) , Frank Scholten (1) , Holger Sierks (3) , Cesare Barbieri (9) , Philippe Lamy (10) , Rafael Rodrigo (11, 12) , Detlef Koschny (13) , Hans Rickman (4, 14) , Michael F. A'Hearn (7) , Maria Antonella Barucci (15) , Jean-Loup Bertaux (16) , Ivano Bertini (6) , Gabriele Cremonese (17) , Vania da Deppo (18) , Stefano Debei (19) , Mariolino de Cecco (20) , Jakob Deller (3) , Sonia Fornasier (15) , Marco Fulle (17) , Olivier Groussin (10) , Pedro J. Gutiérrez (21) , Carsten Güttler (3) , Marc Hofmann (3) , Wing-Huen Ip (22) , Laurent Jorda (10) , Jörg Knollenberg (1) , Jörg Rainer Kramm (3) , Michael Küppers (23) , Luisa M. Lara (21) , Monica Lazzarin (9) , José J. Lopez Moreno (21) , Francesco Marzari (9) , Giampiero Naletto (24, 6, 18) , Cécilia Tubiana (3) , Ncolas Thomas (25, 26)

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

We collect observational evidence that supports the scheme of mass transfer on the nucleus of comet 67P/Churyumov-Gerasimenko. The obliquity of the rotation axis of 67P causes strong seasonal variations. During perihelion the southern hemisphere is four times more active than the north. Northern territories are widely covered by granular material that indicates back fall originating from the active south. Decimetre sized chunks contain water ice and their trajectories are influenced by an anti-solar force instigated by sublimation. OSIRIS observations suggest that up to 20 per cent of the particles directly return to the nucleus surface taking several hours of travel time. The back fall covered northern areas are active if illuminated but produce mainly water vapour. The decimetre chunks from the nucleus surface are too small to contain more volatile compounds such as CO₂ or CO. This causes a north-south dichotomy of the composition measurements in the coma. Active particles are trapped in the gravitational minimum of Hapi during northern winter. They are ‘shock frozen’ and only re-activated when the comet approaches the sun after its aphelion passage. The insolation of the big cavity is enhanced by self-heating, i. e. reflection and IR radiation from the walls. This, together with the pristinity of the active back fall, explains the early observed activity of the Hapi region. Sobek may be a role model for the consolidated bottom of Hapi. Mass transfer in the case of 67P strongly influences the evolution of the nucleus and the interpretation of coma measurements.

Keywords: 67P/Churyumov-Gerasimenko; Data analysis; Comets

Domains: Earth and Planetary Astrophysics [astro-ph.EP]; Solar and Stellar Astrophysics [astro-ph.SR]; Physics [physics]; Astrophysics [astro-ph]

Horst Uwe Keller, Stefano Mottola, Stubbe F. Hviid, Jessica Agarwal, Ekkehard Kührt, et al.. Seasonal Mass Transfer on the Nucleus of Comet 67P/Chuyumov-Gerasimenko. Monthly Notices of the Royal Astronomical Society, 2017, 469 (Suppl_2), pp.S357-S371. ⟨10.1093/mnras/stx1726⟩. ⟨insu-01574799⟩