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) , Giampiero Naletto (7) , Fabrizio Capaccioni (2) , Holger Sierks (1) , Gabriele Arnold (8) , M. Antonella Barucci (9) , Jean-Loup Bertaux (10) , Ivano Bertini (7) , Dennis Bodewits (11) , Maria Teresa Capria (2) , M. Ciarniello (2) , Gabriele Cremonese (12) , Jacques Crovisier (9) , 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 (9) , Gianrico Filacchione (2) , Uwe Fink (17) , M. Formisano (2) , Sonia Fornasier (9) , Pedro J. Gutiérrez (18) , Wing-Huen Ip (19, 20) , Stavro L. Ivanovski (6) , David Kappel (8, 21) , Horst Uwe Keller (22, 8) , Ludmilla Kolokolova (23) , Detlief Koschny (24) , Harald Krueger (1) , Fiorangela La Forgia (7) , Philippe Lamy (10) , Luisa Maria Lara (18) , Monica Lazzarin (7) , Anny Chantal Levasseur-Regourd (10) , Zhong-Yi Lin (19) , A. Longobardo (2, 25) , Josè Juan Lopez-Moreno (18) , Francesco Marzari (7) , Alessandra Migliorini (2) , Stefano Mottola (8) , Rafael Rodrigo (26, 5) , F. Taylor (27) , Imre Toth (28) , V. Zakharov (2) , Dominique Bockelée-Morvan (9)

1 MPS - Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research
2 IAPS - Istituto di Astrofisica e Planetologia Spaziali - INAF
3 IfA - Institute for Astronomy [Edinburgh]
4 Institut für Geodäsie und Geoinformationstechnik
5 ISSI - International Space Science Institute [Bern]
6 OAT - INAF - Osservatorio Astronomico di Trieste
7 Dipartimento di Fisica e Astronomia "Galileo Galilei"
8 DLR Institut für Planetenforschung
9 LESIA (UMR_8109) - Laboratoire d'études spatiales et d'instrumentation en astrophysique
10 PLANETO - LATMOS
11 Department of Physics [Auburn]
12 OAPD - INAF - Osservatorio Astronomico di Padova
13 IFN - CNR Institute for Photonics and Nanotechnologies
14 Department of Industrial Engineering [Padova]
15 UNITN - Università degli Studi di Trento = University of Trento
16 JPL - Jet Propulsion Laboratory
17 LPL - Lunar and Planetary Laboratory [Tucson]
18 IAA - Instituto de Astrofísica de Andalucía
19 IANCU - Institute of Astronomy [Taiwan]
20 SSI - Space Science Institute [Macau]
21 Institut für Physik und Astrophysik [Potsdam]
22 IGEP - Institut für Geophysik und Extraterrestrische Physik [Braunschweig]
23 Department of Astronomy [College Park]
24 RSSD - Research and Scientific Support Department, ESTEC
25 PARTHENOPE - Università degli Studi di Napoli “Parthenope” = University of Naples
26 CAB - Centro de Astrobiologia [Madrid]
27 Department of Physics [Oxford]
28 Konkoly Observatory

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.

Mots clés: Methods: data analysis; Comets: general; Comet: individual: 67P/Churyumov-Gerasimenko

Domaines: Astrophysique [astro-ph]; Physique [physics]

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, 2019, 630, A23 (14 p.). ⟨10.1051/0004-6361/201834869⟩. ⟨insu-02129400⟩