Bidirectional reflectance of laboratory cometary analogues to interpret the spectrophotometric properties of the nucleus of comet 67P/Churyumov-Gerasimenko

Jost, Bernhard; Pommerol, Antoine; Poch, Olivier; Brouet, Yann; Fornasier, Sonia; Carrasco, Nathalie; Szopa, Cyril; Thomas, Nicolas (2017). Bidirectional reflectance of laboratory cometary analogues to interpret the spectrophotometric properties of the nucleus of comet 67P/Churyumov-Gerasimenko. Planetary and space science, 148, pp. 1-11. Elsevier 10.1016/j.pss.2017.09.009

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In this work we provide measurements of the bidirectional reflectance in the VIS-NIR spectral range for a selection of laboratory samples to deduce parameters such as their visible spectrum, phase curve, hemispheric albedo and phase reddening. The aim is to simulate the reflectance of the comet nucleus in order to aid the interpretation of data from the surface of comet 67P/Churyumov-Gerasimenko (67P) acquired by the Rosetta OSIRIS imaging system. We produced a broad variety of well characterised and reproducible samples containing water ice, carbonaceous compounds and complex organic molecules. We were able to reproduce the individual global spectrophotometric parameters (albedo, spectrum, phase reddening, phase curve) of 67P by using mixtures of activated charcoal, tholins and water ice. However, no mixture was able to fit all parameters simultaneously. The samples with highest porosities best match the phase curve of 67P. Spectral considerations from our experiments show that the particle size of the darkening agent on the cometary surface should have a lower limit of a few hundred nanometres to several micrometres and cannot be dominated by particles in the range of some tens of nanometres. Furthermore, our findings indicate that the bright ice patches observed by OSIRIS and VIRTIS should be relatively dust free at small scale.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
08 Faculty of Science > Physics Institute > NCCR PlanetS

UniBE Contributor:

Jost, Bernhard; Pommerol, Antoine; Poch, Olivier; Brouet, Yann and Thomas, Nicolas

Subjects:

500 Science > 520 Astronomy
600 Technology > 620 Engineering

ISSN:

0032-0633

Publisher:

Elsevier

Language:

English

Submitter:

Dora Ursula Zimmerer

Date Deposited:

20 Nov 2017 11:25

Last Modified:

09 Mar 2018 13:08

Publisher DOI:

10.1016/j.pss.2017.09.009

BORIS DOI:

10.7892/boris.106337

URI:

https://boris.unibe.ch/id/eprint/106337

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