Models of Rosetta/OSIRIS 67P dust coma phase function

• Main Authors: Moreno, Fernando, Guirado, Daniel, Muñoz, Olga, Bertini, Ivano, Tubiana, Cecilia, Guttler, Carsten, Fulle, Marco, Rotundi, Alessandra, Della Corte, Vincenzo, Ivanovski, Stavro, Rinaldi, Giovanna, Bockelee-Morvan, Dominique, Zakharov, Vladimir, Agarwal, Jessica, Mottola, Stefano, Toth, Imre, Frattin, Elisa, Lara, Luisa, Gutierrez, Pedro, Lin, Zhong Yi, Kolokolova, Ludmilla, Sierks, Holger, Naletto, Giampiero, Lamy, Philippe, Rodrigo, Rafael, Koschny, Detlef, Davidsson, Bjorn, Barucci, Maria Antonietta, Bertaux, Jean-Lup, Bodewits, Dennis, Cremonese, Gabriele, Da Deppo, Vania, Debei, Stefano, de Cecco, Mariolino, Deller, Jakob, Fornasier, Sonia, Ip, Wing, Keller, Uwe, Lazzarin, Monica, Lopez-Moreno, Jose Juan, Marzari, Francesco, Shi, Xian
• Format: Journal Article
• Language: English
• Published: 27-09-2018
• Subjects: Physics - Earth and Planetary Astrophysics
• DOI: 10.48550/arxiv.1809.10424

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.