Ion composition at comet 67P near perihelion: Rosetta observations and model-based interpretation

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Title: Ion composition at comet 67P near perihelion: Rosetta observations and model-based interpretation
Authors: Heritier, KL
Altwegg, K
Balsiger, H
Berthelier, J-J
Beth, A
Bieler, A
Biver, N
Calmonte, U
Combi, MR
De Keyser, J
Eriksson, AI
Fiethe, B
Fougere, N
Fuselier, SA
Galand, M
Gasc, S
Gombosi, TI
Hansen, KC
Hassig, M
Kopp, E
Odelstad, E
Rubin, M
Tzou, C-Y
Vigren, E
Vuitton, V
Item Type: Journal Article
Abstract: We present the ion composition in the coma of comet 67P with newly detected ion species over the 28–37 u mass range, probed by Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA)/Double Focusing Mass Spectrometer (DFMS). In summer 2015, the nucleus reached its highest outgassing rate and ion-neutral reactions started to take place at low cometocentric distances. Minor neutrals can efficiently capture protons from the ion population, making the protonated version of these neutrals a major ion species. So far, only NH+4 has been reported at comet 67P. However, there are additional neutral species with proton affinities higher than that of water (besides NH3) that have been detected in the coma of comet 67P: CH3OH, HCN, H2CO and H2S. Their protonated versions have all been detected. Statistics showing the number of detections with respect to the number of scans are presented. The effect of the negative spacecraft potential probed by the Rosetta Plasma Consortium/LAngmuir Probe on ion detection is assessed. An ionospheric model has been developed to assess the different ion density profiles and compare them to the ROSINA/DFMS measurements. It is also used to interpret the ROSINA/DFMS observations when different ion species have similar masses, and their respective densities are not high enough to disentangle them using the ROSINA/DFMS high-resolution mode. The different ion species that have been reported in the coma of 67P are summarized and compared with the ions detected at comet 1P/Halley during the Giotto mission.
Issue Date: 27-Jul-2017
Date of Acceptance: 25-Jul-2017
ISSN: 0035-8711
Publisher: Oxford University Press
Start Page: S427
End Page: S442
Journal / Book Title: Monthly Notices of the Royal Astronomical Society
Volume: 469
Issue: Suppl_2
Copyright Statement: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society©2017 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Sponsor/Funder: Imperial College Trust
Science and Technology Facilities Council (STFC)
European Space Agency / Estec
Funder's Grant Number: N/A
Keywords: 0201 Astronomical And Space Sciences
Astronomy & Astrophysics
Publication Status: Published
Appears in Collections:Space and Atmospheric Physics
Faculty of Natural Sciences

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