Dark side of comet 67P/Churyumov-Gerasimenko in Aug.–Oct. 2014

Autor: Wing-Huen Ip, Laurent Jorda, Christopher Jarchow, F. P. Schloerb, Holger Sierks, C. Leyrat, Pierre Encrenaz, Samuel Gulkis, Jacques Crovisier, M. A. Janssen, Mark Hofstadter, Emmanuel Lellouch, P. von Allmen, B. Gaskell, Sukhan Lee, Mathieu Choukroun, Paul Hartogh, Horst Uwe Keller, N. Biver, Dominique Bockelée-Morvan, Stephen Keihm, Ladislav Rezac, Gerard Beaudin
Přispěvatelé: Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)
Rok vydání: 2015
Předmět:
Zdroj: Astronomy and Astrophysics-A&A
Astronomy and Astrophysics-A&A, EDP Sciences, 2015, 583, ⟨10.1051/0004-6361/201526181⟩
Astronomy and Astrophysics-A&A, 2015, 583, ⟨10.1051/0004-6361/201526181⟩
ISSN: 1432-0746
0004-6361
DOI: 10.1051/0004-6361/201526181
Popis: International audience; The high obliquity (similar to 50 degrees) of comet 67P/Churyumov-Gerasimenko (67P) is responsible for a long-lasting winter polar night in the southern regions of the nucleus. We report observations made with the submillimeter and millimeter continuum channels of the Microwave Instrument onboard the Rosetta Orbiter (MIRO) of the thermal emission from these regions during the period August-October 2014. Before these observations, the southern polar regions had been in darkness for approximately five years. Subsurface temperatures in the range 25 50 K are measured. Thermal model calculations of the nucleus near-surface temperatures carried out over the orbit of 67P, coupled with radiative transfer calculations of the MIRO channels brightness temperatures, suggest that these regions have a thermal inertia within the range 10-60 Jm(-2) K-1 s(-0.5). Such low thermal inertia values are consistent with a highly porous, loose, regolith-like surface. These values are similar to those derived elsewhere on the nucleus. A large difference in the brightness temperatures measured by the two MIRO continuum channels is tentatively attributed to dielectric properties that differ significantly from the sunlit side, within the first few tens of centimeters. This is suggestive of the presence of ice(s) within the MIRO depths of investigation in the southern polar regions. These regions started to receive sunlight in May of 2015, and refinements of the shape model in these regions, as well as continuing MIRO observations of 67P, will allow refining these results and reveal the thermal properties and potential ice content of the southern regions in more detail.
Databáze: OpenAIRE
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