Long term survival of surface water ice on comet 67P

Nilda Oklay (1) , Stefano Mottola (1) , Jean-Baptiste Vincent (1) , Maurizio Pajola (2) , Sonia Fornasier (3) , Stubbe F. Hviid (1) , David Kappel (1) , Ekkehard Kührt (1) , Horst Uwe Keller (4) , Maria Antonella Barucci (3) , Clément Feller (3) , Frank Preusker (1) , Frank Scholten (1) , I. Hall (5) , Holger Sierks (5) , Cesare Barbieri (6) , Philippe L. Lamy (7) , Rafael Rodrigo (8, 9) , Detlef Koschny (10) , Hans Rickman (11, 12) , Michael F. A'Hearn (13) , Jean-Loup Bertaux (14) , Ivano Bertini (15) , Dennis Bodewits (13) , Gabriele Cremonese (16) , Vania da Deppo (17) , Björn J. R. Davidsson (18) , Stefano Debei (19) , Mariolino de Cecco (20) , Johannes Deller (5) , J. D. P. Deshapriya (3) , Marco Fulle (21) , Adeline Gicquel (18) , Olivier Groussin (7) , Pedro J. Gutiérrez (22) , Carsten Güttler (5) , Pedro Henrique Hasselmann (3) , M. Hofmann (5) , W.-H. Ip (23) , Laurent Jorda (7) , J. Knollenberg (1) , G. Kovacs (5) , J.-R. Kramm (5) , M. Küppers (24) , Luisa M. Lara (22) , M. Lazzarin (6) , Z.-Y. Lin (23) , J. J. Lopez Moreno (22) , A. Lucchetti (16) , F. Marzari (6) , N. Masoumzadeh (5) , G. Naletto (25, 15, 17) , A. Pommerol (26) , X. Shi (5) , Nicholas Thomas (26) , Cecilia Tubiana (5)

1 DLR Institut für Planetenforschung
2 ARC - NASA Ames Research Center
3 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
4 IGEP - Institut für Geophysik und Extraterrestrische Physik [Braunschweig]
5 MPS - Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research
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 Department of Physics and Astronomy [Uppsala]
12 CBK - Space Research Centre of Polish Academy of Sciences
13 Department of Astronomy [College Park]
14 PLANETO - LATMOS
15 CISAS - Centro di Ateneo di Studi e Attività Spaziali “Giuseppe Colombo”
16 OAPD - INAF - Osservatorio Astronomico di Padova
17 IFN - CNR Institute for Photonics and Nanotechnologies
18 JPL - Jet Propulsion Laboratory
19 Department of Industrial Engineering [Padova]
20 UNITN - Università degli Studi di Trento = University of Trento
21 OAT - INAF - Osservatorio Astronomico di Trieste
22 IAA - Instituto de Astrofísica de Andalucía
23 Institute of Space Science [Taiwan]
24 Operations Department (ESAC)
25 DEI - Department of Information Engineering [Padova]
26 Physikalisches Institut [Bern]

Numerous water-ice-rich deposits surviving more than several months on comet 67P/Churyumov-Gerasimenko were observed during the Rosetta mission. We announce the first-time detection of water ice features surviving up to two years since their first observation via OSIRIS NAC. Their existence on the nucleus of comet 67P at the arrival of the Rosetta spacecraft suggests that they were exposed to the surface during the comet’s previous orbit. We investigated the temporal variation of large water ice patches to understand the long-term sustainability of water ice on cometary nuclei on time scales of months and years. Large clusters are stable over typical periods of 0.5 year and reduce their size significantly around the comet’s perihelion passage, while small exposures disappear. We characterized the temporal variation of their multispectral signatures. In large clusters, dust jets were detected, whereas in large isolated ones no associated activity was detected. Our thermal analysis shows that the long-term sustainability of water-ice-rich features can be explained by the scarce energy input available at their locations over the first half year. However, the situation reverses for the period lasting several months around perihelion passage. Our two end-member mixing analysis estimates a pure water-ice equivalent thickness up to 15 cm within one isolated patch, and up to 2 m for the one still observable through the end of the mission. Our spectral modelling estimates up to 48% water-ice content for one of the large isolated feature, and up to 25% water ice on the large boulders located within clusters.

Domaines: Planétologie et astrophysique de la terre [astro-ph.EP]; Astrophysique stellaire et solaire [astro-ph.SR]

Nilda Oklay, Stefano Mottola, Jean-Baptiste Vincent, Maurizio Pajola, Sonia Fornasier, et al.. Long term survival of surface water ice on comet 67P. Monthly Notices of the Royal Astronomical Society, 2017, 469 (Suppl_2), pp.S582-S597. ⟨10.1093/mnras/stx2298⟩. ⟨insu-01587261⟩