SUBSURFACE CHARACTERIZATION OF 67P/CHURYUMOV–GERASIMENKO’S ABYDOS SITE

Journal Article · Tue May 10 00:00:00 EDT 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/822/2/98· OSTI ID:22663040

Brugger, B.; Mousis, O.; Jorda, L.; Lamy, P.; Vernazza, P. ^[1]; Morse, A.; Andrews, D.; Barber, S.; Morgan, G.; Sheridan, S.; Wright, I. P. ^[2]; Marboeuf, U. ^[3]; Guilbert-Lepoutre, A. ^[4]; Luspay-Kuti, A.

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1. Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, F-13388, Marseille (France)
2. Planetary and Space Sciences, Department of Physics, The Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom)
3. Physikalishes Institut, Center for Space and Habitability, University of Bern (Switzerland)
4. Institut UTINAM, UMR 6213 CNRS-Université de Franche-Comté, Besançon (France)

On 2014 November 12, the ESA/ Rosetta descent module Philae landed on the Abydos site of comet 67P/Churyumov–Gerasimenko. Aboard this module, the Ptolemy mass spectrometer measured a CO/CO{sub 2} ratio of 0.07 ± 0.04, which differs substantially from the value obtained in the coma by the Rosetta /ROSINA instrument, suggesting a heterogeneity in the comet nucleus. To understand this difference, we investigated the physicochemical properties of the Abydos subsurface, leading to CO/CO{sub 2} ratios close to that observed by Ptolemy at the surface of this region. We used a comet nucleus model that takes into account different water ice phase changes (amorphous ice, crystalline ice, and clathrates) as well as diffusion of molecules throughout the pores of the matrix. The input parameters of the model were optimized for the Abydos site, and the ROSINA CO/CO{sub 2} measured ratio is assumed to correspond to the bulk value in the nucleus. We find that all considered structures of water ice are able to reproduce the Ptolemy observation with a time difference not exceeding ∼50 days, i.e., lower than ∼2% on 67P/Churyumov–Gerasimenko’s orbital period. The suspected heterogeneity of 67P/Churyumov–Gerasimenko’s nucleus is also found possible only if it is constituted of crystalline ices. If the icy phase is made of amorphous ice or clathrates, the difference between Ptolemy and ROSINA’s measurements would rather originate from the spatial variations in illumination on the nucleus surface. An eventual new measurement of the CO/CO{sub 2} ratio at Abydos by Ptolemy could be decisive to distinguish between the three water ice structures.

• OSTI ID: 22663040
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 822; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
79 ASTRONOMY AND ASTROPHYSICS
CARBON
CARBON DIOXIDE
CARBON MONOXIDE
COMETS
CONCENTRATION RATIO
DIFFUSION
ICE
MASS
MASS SPECTROMETERS
MOLECULES
NUCLEI
WATER