The Opposition Effect of 67P/Churyumov-Gerasimenko on post-perihelion Rosetta images - Archive ouverte HAL Access content directly
Journal Articles Monthly Notices of the Royal Astronomical Society Year : 2017

The Opposition Effect of 67P/Churyumov-Gerasimenko on post-perihelion Rosetta images

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Bernhard Jost
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Philippe Lamy
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Jean-Loup Bertaux
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  • PersonId : 914210
Gabriele Cremonese
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  • PersonId : 1005814
Olivier Groussin
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  • PersonId : 837612
Pedro J. Gutiérrez
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  • PersonId : 880386
Laurent Jorda
Michael Küppers
Nilda Oklay
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  • PersonId : 976656
Nicolas Thomas
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  • PersonId : 963386

Abstract

High-resolution OSIRIS/Rosetta images of 67P/Churyumov-Gerasimenko acquired on the night run of April 9th to 10th 2016 shows, at large scale, an Opposition Effect (OE) spot swooping across Imhotep as the phase angle ranges from 0° to 17°. In this work, we fitted the phase curve of the whole surface imaged as well as three particular features using both linear-exponential and Hapke (2012) model. Those features encompass different types of spectral behaviour: a circular mesa, one venous structure and an assemble of bright spots, going from red to blue colours. Both Hapke and linear-exponential parameters indicate a stepwise sharpening of the OE from bright spots to circular mesa. Yet, a very broad non-linear phase curve is verified and no sign of sharp OE associated to coherent-backscattering mechanism observed. We estimate that 67P surface is dominated by opaque, desiccated and larger-than-wavelength irregular grains. Veins and bright spots display photometric properties consistent to surfaces becoming slightly brighter as it is 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 (Fornasier et al., 2015) 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 Imhotep-Ash boundary area (Feller et al., 2016) advocates for mild darkening (< 7%) of the surface at local scale.
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Dates and versions

insu-01599000 , version 1 (09-05-2018)

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Pedro Henrique Hasselmann, Maria Antonella Barucci, Sonia Fornasier, Clément Feller, Prasanna Deshapriya, et al.. The Opposition Effect of 67P/Churyumov-Gerasimenko on post-perihelion Rosetta images . Monthly Notices of the Royal Astronomical Society, 2017, 469 (Suppl_2), pp.S550-S567. ⟨10.1093/mnras/stx1834⟩. ⟨insu-01599000⟩
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