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Evolution Of The Dust Size Distribution Of Comet 67P/Churyumov-Gerasimenko From 2.2 Au To Perihelion
INAF Osservatorio Astron, Via Tiepolo 11, I-34143 Trieste, Italy..
Univ Padua, Dept Phys, I-35131 Padua, Italy..
INAF Ist Astrofis & Planetol Spaziali, Via Fosso del Cavaliere 100, I-00133 Rome, Italy..
Univ Paris 06, Univ Paris 04, Univ Paris Diderot, Observ Paris,LESIA,Observ Paris,PSL Res Univ,CNRS, 5 Pl J Janssen, F-92195 Meudon, France..
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2016 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 821, no 1, 19Article in journal (Refereed) PublishedText
Abstract [en]

The Rosetta probe, orbiting Jupiter-family comet 67P/Churyumov-Gerasimenko, has been detecting individual dust particles of mass larger than 10(-10) kg by means of the GIADA dust collector and the OSIRIS Wide Angle Camera and Narrow Angle Camera since 2014 August and will continue until 2016 September. Detections of single dust particles allow us to estimate the anisotropic dust flux from 67P, infer the dust loss rate and size distribution at the surface of the sunlit nucleus, and see whether the dust size distribution of 67P evolves in time. The velocity of the Rosetta orbiter, relative to 67P, is much lower than the dust velocity measured by GIADA, thus dust counts when GIADA is nadir-pointing will directly provide the dust flux. In OSIRIS observations, the dust flux is derived from the measurement of the dust space density close to the spacecraft. Under the assumption of radial expansion of the dust, observations in the nadir direction provide the distance of the particles by measuring their trail length, with a parallax baseline determined by the motion of the spacecraft. The dust size distribution at sizes > 1 mm observed by OSIRIS is consistent with a differential power index of -4, which was derived from models of 67P's trail. At sizes <1 mm, the size distribution observed by GIADA shows a strong time evolution, with a differential power index drifting from -2 beyond 2 au to -3.7 at perihelion, in agreement with the evolution derived from coma and tail models based on ground-based data. The refractory-to-water mass ratio of the nucleus is close to six during the entire inbound orbit and at perihelion.

Place, publisher, year, edition, pages
2016. Vol. 821, no 1, 19
Keyword [en]
comets: general, comets: individual (67P/Churyumov-Gerasimenko), space vehicles: instruments
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:uu:diva-300292DOI: 10.3847/0004-637X/821/1/19ISI: 000373809000019OAI: oai:DiVA.org:uu-300292DiVA: diva2:951330
Swedish National Space Board
Available from: 2016-08-08 Created: 2016-08-08 Last updated: 2016-08-08Bibliographically approved

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Rickman, HansDavidsson, Björn
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