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Diurnal variation of dust and gas production in comet 67P/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. Gutiérrez 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 1 Fiorangela La Forgia 8 Philippe Lamy 10 Luisa Maria Lara 18 Monica Lazzarin 8 Anny Chantal Levasseur-Regourd 10 Zhong-Yi Lin 19 A. Longobardo 2, 25 Josè Juan Lopez-Moreno 18 Francesco Marzari 8 Alessandra Migliorini 2 Stefano Mottola 9 Rafael Rodrigo 26, 5 F. Taylor 27 Imre Toth 28 V. Zakharov 2
Abstract : On 27 April 2015, when comet 67P/Churyumov-Gerasimenko was at 1.76 au from the Sun and moving toward perihelion, the OSIRIS and VIRTIS-M instruments on board the Rosetta spacecraft simultaneously observed the evolving dust and gas coma during a complete rotation of the comet. We aim to characterize the spatial distribution of dust, H2O, and CO2 gas in the inner coma. To do this, we performed a quantitative analysis of the release of dust and gas and compared the observed H2O production rate with the rate we calculated using a thermophysical model. 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 (CO2 emission band). We measured the average signal in a circular annulus to study the spatial variation around the comet, and in a sector 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 comet center. The spatial correlation between dust and water, both coming from the sunlit side of the comet, shows that water is the main driver of dust activity in this time period. The spatial distribution of CO2 is not correlated with water and dust. There is no strong temporal correlation between the dust brightness and water production rate as the comet rotates. The dust brightness shows a peak at 0° subsolar longitude, which is not pronounced in the water production. At the same epoch, there is also a maximum in CO2 production. An excess of measured water production with respect to the value calculated using a simple thermophysical model is observed when the head lobe and regions of the southern hemisphere with strong seasonal variations are illuminated (subsolar longitude 270°–50°). A drastic decrease in dust production when the water production (both measured and from the model) displays a maximum occurs when typical northern consolidated regions are illuminated and the southern hemisphere regions with strong seasonal variations are instead in shadow (subsolar longitude 50°–90°). Possible explanations of these observations are presented and discussed.
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Cécilia Tubiana, Giovanna Rinaldi, Carsten Güttler, Colin Snodgrass, Xian Shi, et al.. Diurnal variation of dust and gas production in comet 67P/Churyumov-Gerasimenko at the inbound equinox as seen by OSIRIS and VIRTIS-M on board Rosetta. Astronomy and Astrophysics - A&A, EDP Sciences, 2019, 630, A23 (14 p.). ⟨10.1051/0004-6361/201834869⟩. ⟨insu-02129400⟩

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