Abundant molecular oxygen in the coma of comet 67P/Churyumov–Gerasimenko

Andre Bieler (1, 2) , Kathrin Altwegg (2, 3) , Hans Balsiger (2) , Akiva Bar-Nun (4) , Jean-Jacques Berthelier (5) , P. Bochsler (2) , Christelle Briois (6) , Ursina Calmonte (2) , M. Combi (1) , J. de Keyser (7) , E. van Dishoeck (8) , B. Fiethe (9) , S. A. Fuselier (10) , S. Gasc (2) , Tamas I. Gombosi (1) , K.C. Hansen (1) , Myrtha Hässig (2, 11) , A. Jäckel (2) , E. Kopp (2) , A. Korth (12) , Léna Le Roy (3) , U. Mall (12) , R. Maggiolo (7) , Bernard Marty (13) , Olivier Mousis (14) , T. Owen (15) , Henri Rème (16) , Martin Rubin (2) , T. Sémon (2) , C.-Y. Tzou (2) , J. Waite (11) , C. Walsh (8) , P. Wurz (2, 3)

1 CLaSP - Department of Climate and Space Sciences and Engineering
2 Physikalisches Institut [Bern]
3 CSH - Center for Space and Habitability
4 TAU - Department of Geophysics [Tel Aviv]
5 PLANETO - LATMOS
6 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace
7 BIRA-IASB - Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique
8 Leiden Observatory [Leiden]
9 IDA - Institute of Computer and Network Engineering [Braunschweig]
10 Space Science and Engineering Division [San Antonio]
11 Space Science Division [San Antonio]
12 MPS - Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research
13 CRPG - Centre de Recherches Pétrographiques et Géochimiques
14 LAM - Laboratoire d'Astrophysique de Marseille
15 University of Hawaii
16 IRAP - Institut de recherche en astrophysique et planétologie

The composition of the neutral gas comas of most comets is dominated by H2O,CO and CO2, typically comprising as much as 95 per cent of the total gas density1. In addition, cometary comas have been found to contain a rich array of other molecules, including sulfuric compounds and complex hydrocarbons. Molecular oxygen (O2), however, despite its detection on other icy bodies such as the moons of Jupiter and Saturn2,3, has remained undetected in cometary comas. Here we report in situ measurement of O2 in the coma of comet 67P/Churyumov–Gerasimenko, with local abundances ranging from one per cent to ten per cent relative to H2O and with a mean value of 3.8060.85 per cent. Our observations indicate that the O2/H2O ratio is isotropic in the coma and does not change systematically with heliocentric distance. This suggests that primordial O2 was incorporated into the nucleus during the comet’s formation, which is unexpected given the low upper limits from remote sensing observations4. Current Solar System formation models do not predict conditions that would allow this to occur.

Domaines: Géochimie; Planétologie; Paléontologie; Planétologie et astrophysique de la terre [astro-ph.EP]

Andre Bieler, Kathrin Altwegg, Hans Balsiger, Akiva Bar-Nun, Jean-Jacques Berthelier, et al.. Abundant molecular oxygen in the coma of comet 67P/Churyumov–Gerasimenko. Nature, 2015, 526 (7575), pp.678-681. ⟨10.1038/nature15707⟩. ⟨hal-01346075⟩