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arXiv · 1809.10424

Models of Rosetta/OSIRIS 67P dust coma phase function

Abstract

The phase function of the dust coma of comet 67P has been determined from Rosetta/OSIRIS images \citep{Bertini17}. This function show a deep minimum at phase angles near 100$^\circ$, and a strong backscattering enhancement. These two properties cannot be reproduced by regular models of cometary dust, most of them based on wavelength-sized and randomly-oriented aggregate particles. We show, however, that an ensamble of oriented elongated particles of a wide variety of aspect ratios, with radii $r \gtrsim$10 $\mu$m, and whose long axes are perpendicular to the direction of the solar radiation, are capable of reproducing the observed phase function. These particles must be absorbing, with an imaginary part of the refractive index of about 0.1 to match the expected geometric albedo, and with porosity in the 60-70\% range.

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Fernando Moreno, Daniel Guirado, Olga Muñoz, Ivano Bertini, Cecilia Tubiana, Carsten Guttler, Marco Fulle, Alessandra Rotundi, Vincenzo Della Corte, Stavro Ivanovski, Giovanna Rinaldi, Dominique Bockelee-Morvan, Vladimir Zakharov, Jessica Agarwal, Stefano Mottola, Imre Toth, Elisa Frattin, Luisa Lara, Pedro Gutierrez, Zhong Yi Lin, Ludmilla Kolokolova, Holger Sierks, Giampiero Naletto, Philippe Lamy, Rafael Rodrigo, Detlef Koschny, Bjorn Davidsson, Maria Antonietta Barucci, Jean-Lup Bertaux, Dennis Bodewits, Gabriele Cremonese, Vania Da Deppo, Stefano Debei, Mariolino de Cecco, Jakob Deller, Sonia Fornasier, Wing Ip, Uwe Keller, Monica Lazzarin, Jose Juan Lopez-Moreno, Francesco Marzari, Xian Shi. 2018-09-27. Models of Rosetta/OSIRIS 67P dust coma phase function. https://doi.org/10.3847/1538-3881/aae526

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