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The opposition effect of 67P/Churyumov-Gerasimenko on post-perihelion Rosetta images
Sorbonne Univ, UPMC Univ Paris 06, Univ Paris Diderot, PSL Res Univ,Sorbonne Paris Cite,Observ Paris,LES, 5 Pl J Janssen, F-92195 Meudon, France.
Sorbonne Univ, UPMC Univ Paris 06, Univ Paris Diderot, PSL Res Univ,Sorbonne Paris Cite,Observ Paris,LES, 5 Pl J Janssen, F-92195 Meudon, France.
Sorbonne Univ, UPMC Univ Paris 06, Univ Paris Diderot, PSL Res Univ,Sorbonne Paris Cite,Observ Paris,LES, 5 Pl J Janssen, F-92195 Meudon, France.
Sorbonne Univ, UPMC Univ Paris 06, Univ Paris Diderot, PSL Res Univ,Sorbonne Paris Cite,Observ Paris,LES, 5 Pl J Janssen, F-92195 Meudon, France.
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2017 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 469, p. S550-S567Article in journal (Refereed) Published
Abstract [en]

High-resolution OSIRIS/Rosetta images of 67P/Churyumov-Gerasimenko acquired on the night run of 2016 April 9-10 show, at large scale, an opposition effect (OE) spot sweeping across Imhotep as the phase angle ranges from 0 degrees to 17 degrees. In this work, we fitted the phase curve of the whole surface imaged as well as three particular features using both the linear-exponential and Hapke models. These features encompass different types of spectral behaviour: a circular mesa, one venous structure and an assemblage of bright spots, going from red to blue colours. Both the Hapke and linear-exponential parameters indicate a stepwise sharpening of the OE from bright spots to circular mesa. Yet a very broad nonlinear phase curve is verified and no sign of sharp OE associated with a coherent-backscattering mechanism is observed. We estimate that the 67P surface is dominated by opaque, desiccated and larger-than-wavelength irregular grains. Veins and bright spots display photometric properties consistent with surfaces becoming slightly brighter as they are enriched by high-albedo ice grains. We also report the estimation of normal albedo for all cometary regions observed throughout the image sequence. Comparison to pre-perihelion results indicates that far better insolation of northern brighter regions, i.e. Hapi, Hathor and Seth, is sufficient to explain mismatches on the photometric parameters. However, metre-scale photometric analysis of the Imhotep-Ash boundary area advocates for mild darkening (<7 per cent) of the surface at local scale.

Place, publisher, year, edition, pages
OXFORD UNIV PRESS , 2017. Vol. 469, p. S550-S567
Keywords [en]
Rosetta: 67P/Churyumov-Gerasimenko, photometry
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:uu:diva-376690DOI: 10.1093/mnras/stx1834ISI: 000443940500051OAI: oai:DiVA.org:uu-376690DiVA, id: diva2:1288525
Conference
International Conference on Cometary Science - Comets - A New Vision after Rosetta and Philae, NOV 14-18, 2016, Toulouse, FRANCE
Available from: 2019-02-13 Created: 2019-02-13 Last updated: 2019-02-13Bibliographically approved

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Rickman, Hans

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