Changes in the Physical Environment of the Inner Coma of 67P/Churyumov–Gerasimenko with Decreasing Heliocentric Distance

Dennis Bodewits (1) , Luisa M. Lara (2) , Michael F. A'Hearn (3, 1) , Florangela La Forgia (4) , Adeline Gicquel (5) , Gabor Kovacs (5) , Jörg Knollenberg (6) , Monica Lazzarin (4) , Zhong-Yi Lin (7) , Xian Shi (5) , Colin Snodgrass (8) , Cécilia Tubiana (5) , Holger Sierks (5) , Cesare Barbieri (4) , Laurent Lamy (9) , Rafael Rodrigo (10, 11) , Detlef Koschny (12) , Hans Rickman (13) , Horst Uwe Keller (14) , Maria Antonietta Barucci (15) , Jean-Loup Bertaux (16) , Ivano Bertini (17) , Steve Boudreault (5) , Gabriele Cremonese (18) , Vania da Deppo (19) , Björn Davidsson (13) , Stefano Debei (20) , Mariolino de Cecco (21) , Sonia Fornasier (15) , Marco Fulle (22) , Olivier Groussin (9) , Pedro J. Gutiérrez (2) , Carsten Güttler (5) , Stubbe F. Hviid (6) , Wing-Huen Ip (7) , Laurent Jorda (9) , J.-Rainer Kramm (5) , Ekkehard Kührt (6) , Michael Küppers (23) , José-Juan López-Moreno (2) , Francesco Marzari (4) , Giampiero Naletto (17, 24, 19) , Nilda Oklay (5) , Nicholas Thomas (25) , Imre Toth (26) , Jean-Baptiste Vincent (5)

1 Department of Astronomy [College Park]
2 IAA - Instituto de Astrofísica de Andalucía
3 Gauss Professor Akademie der Wissenschaften zu Göttingen
4 Dipartimento di Fisica e Astronomia "Galileo Galilei"
5 MPS - Max-Planck-Institut für Sonnensystemforschung
6 DLR Institut für Planetenforschung
7 IANCU - Institute of Astronomy [Taiwan]
8 School of Physical Sciences [Milton Keynes]
9 LAM - Laboratoire d'Astrophysique de Marseille
10 CAB - Centro de Astrobiologia [Madrid]
11 ISSI - International Space Science Institute [Bern]
12 ESTEC - European Space Research and Technology Centre
13 Department of Physics and Astronomy [Uppsala]
14 IGEP - Institut für Geophysik und Extraterrestrische Physik [Braunschweig]
15 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
16 PLANETO - LATMOS
17 CISAS - Centro di Ateneo di Studi e Attività Spaziali “Giuseppe Colombo”
18 OAPD - INAF - Osservatorio Astronomico di Padova
19 IFN - CNR Institute for Photonics and Nanotechnologies
20 Department of Mechanical Engineering [Padova]
21 University of Trento [Trento]
22 OAT - INAF - Osservatorio Astronomico di Trieste
23 Operations Department (ESAC)
24 DEI - Department of Information Engineering [Padova]
25 Physikalisches Institut [Bern]
26 Konkoly Observatory

The Wide Angle Camera of the OSIRIS instrument on board the Rosetta spacecraft is equipped with several narrow-band filters that are centered on the emission lines and bands of various fragment species. These are used to determine the evolution of the production and spatial distribution of the gas in the inner coma of comet 67P with time and heliocentric distance, here between 2.6 and 1.3 au pre-perihelion. Our observations indicate that the emission observed in the OH, O i, CN, NH, and NH₂ filters is mostly produced by dissociative electron impact excitation of different parent species. We conclude that CO₂ rather than H₂O is a significant source of the [O i] 630 nm emission. A strong plume-like feature observed in the CN and O i filters is present throughout our observations. This plume is not present in OH emission and indicates a local enhancement of the CO₂/H₂O ratio by as much as a factor of 3. We observed a sudden decrease in intensity levels after 2015 March, which we attribute to decreased electron temperatures in the first few kilometers above the surface of the nucleus.

Keywords: comets

Domains: Sciences of the Universe [physics]; Astrophysics [astro-ph]; Earth and Planetary Astrophysics [astro-ph.EP]

Dennis Bodewits, Luisa M. Lara, Michael F. A'Hearn, Florangela La Forgia, Adeline Gicquel, et al.. Changes in the Physical Environment of the Inner Coma of 67P/Churyumov–Gerasimenko with Decreasing Heliocentric Distance. The Astronomical Journal, 2016, 152 (5), pp.130. ⟨10.3847/0004-6256/152/5/130⟩. ⟨insu-01388677⟩