Diurnal variation of dust and gas production in comet67P/Churyumov-Gerasimenko at the inbound equinox as seen by OSIRIS and VIRTIS-M on board Rosetta

Cécilia Tubiana 1 Giovanna Rinaldi 2 Carsten Güttler 1 Colin Snodgrass 3 Xian Shi 1 Xuanyu Hu 4 R. Marschall 5 Marco Fulle 6 Dominique Bockelée-Morvan 7 Giampiero Naletto 8 Fabrizio Capaccioni 2 Holger Sierks 1 Gabriele Arnold 9 M. Antonella Barucci 7 Jean-Loup Bertaux 10 Ivano Bertini 8 Dennis Bodewits 11 Maria Teresa Capria 2 M. Ciarniello 2 Gabriele Cremonese 12 Jacques Crovisier 7 Vania da Deppo 13 Stefano Debei 14 Mariolino de Cecco 15 Jakob Deller 1 M.C. de Sanctis 2 Björn Davidsson 16 L. Doose 17 Stéphane Erard 7 Gianrico Filacchione 2 Uwe Fink 17 M. Formisano 2 Sonia Fornasier 7 Pedro J. Gutierrez 18 Wing-Huen Ip 19, 20 Stavro L. Ivanovski 6 David Kappel 9, 21 Horst Uwe Keller 22, 9 Ludmilla Kolokolova 23 Detlief Koschny 24 Harald Krueger 25, 1 Fiorangela La Forgia 8 Philippe Lamy 10 Luisa Maria Lara 18 Monica Lazzarin 8 Anny Chantal Levasseur-Regourd 10 Zhong-Yi Lin 26 A. Longobardo 2, 27 Josè Juan Lopez-Moreno 18 Francesco Marzari 8 Alessandra Migliorini 2 Stefano Mottola 9 Rafael Rodrigo 28, 5 F. Taylor 29 Imre Toth 30 V. Zakharov 2
Abstract : On 27 April 2015, when 67P/Churyumov-Gerasimenko was at 1.76 au from the Sun and moving towards perihelion, the OSIRIS andVIRTIS-M instruments on board Rosetta simultaneously observed the evolving dust and gas coma during a complete rotation of the comet.Aims.We aim to characterize the dust, H2O and CO2gas spatial distribution in the inner coma. To do this we performed a quantitative analysis ofthe release of dust and gas and compared the observed H2O production rate with the one calculated using a thermo-physical model.Methods.For this study we selected OSIRIS WAC images at 612 nm (dust) and VIRTIS-M image cubes at 612 nm, 2700 nm (H2O emission band)and 4200 nm (CO2emission band). We measured the average signal in a circular annulus, to study spatial variation around the comet, and in asector of the annulus, to study temporal variation in the sunward direction with comet rotation, both at a fixed distance of 3.1 km from the cometcentre.Results.The spatial correlation between dust and water, both coming from the sun-lit side of the comet, shows that water is the main driver ofdust activity in this time period. The spatial distribution of CO2is not correlated with water and dust. There is no strong temporal correlationbetween the dust brightness and water production rate as the comet rotates. The dust brightness shows a peak at 0◦sub-solar longitude, whichis not pronounced in the water production. At the same epoch, there is also a maximum in CO2production. An excess of measured waterproduction, with respect to the value calculated using a simple thermo-physical model, is observed when the head lobe and regions of the Southernhemisphere with strong seasonal variations are illuminated (sub-solar longitude 270◦– 50◦). A drastic decrease in dust production, when the waterproduction (both measured and from the model) displays a maximum, happens when typical Northern consolidated regions are illuminated andthe Southern hemisphere regions with strong seasonal variations are instead in shadow (sub-solar longitude 50◦– 90◦). Possible explanations ofthese observations are presented and discussed.
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Submitted on : Tuesday, May 14, 2019 - 8:56:43 PM
Last modification on : Tuesday, August 27, 2019 - 11:54:06 AM

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  • HAL Id : insu-02129400, version 1
  • ARXIV : 1905.03022

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Cécilia Tubiana, Giovanna Rinaldi, Carsten Güttler, Colin Snodgrass, Xian Shi, et al.. Diurnal variation of dust and gas production in comet67P/Churyumov-Gerasimenko at the inbound equinox as seen by OSIRIS and VIRTIS-M on board Rosetta. Astronomy and Astrophysics - A&A, EDP Sciences, 2019, (in press). ⟨insu-02129400⟩

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