ALBERT

Description: 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 density. 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 Saturn, 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 3.80 +/- 0.85 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 observations. Current Solar System formation models do not predict conditions that would allow this to occur.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bieler, A -- Altwegg, K -- Balsiger, H -- Bar-Nun, A -- Berthelier, J-J -- Bochsler, P -- Briois, C -- Calmonte, U -- Combi, M -- De Keyser, J -- van Dishoeck, E F -- Fiethe, B -- Fuselier, S A -- Gasc, S -- Gombosi, T I -- Hansen, K C -- Hassig, M -- Jackel, A -- Kopp, E -- Korth, A -- Le Roy, L -- Mall, U -- Maggiolo, R -- Marty, B -- Mousis, O -- Owen, T -- Reme, H -- Rubin, M -- Semon, T -- Tzou, C-Y -- Waite, J H -- Walsh, C -- Wurz, P -- England -- Nature. 2015 Oct 29;526(7575):678-81. doi: 10.1038/nature15707.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Climate and Space Science and Engineering, University of Michigan, 2455 Hayward Street, Ann Arbor, Michigan 48109, USA. ; Physikalisches Institut, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland. ; Center for Space and Habitability, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland. ; Department of Geosciences, Tel-Aviv University, Ramat-Aviv, 6997801 Tel-Aviv, Israel. ; LATMOS/IPSL-CNRS-UPMC-UVSQ, 4 Avenue de Neptune, F-94100 Saint-Maur, France. ; Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), UMR 6115 CNRS - Universite d'Orleans, 45071 Orleans, France. ; Belgian Institute for Space Aeronomy, BIRA-IASB, Ringlaan 3, B-1180 Brussels, Belgium. ; Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands. ; Institute of Computer and Network Engineering (IDA), TU Braunschweig, Hans-Sommer-Strasse 66, D-38106 Braunschweig, Germany. ; Space Science and Engineering Division, Southwest Research Institute, 6220 Culebra Road, San Antonio, Texas 78228, USA. ; Max-Planck-Institut fur Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Gottingen, Germany. ; Centre de Recherches Petrographiques et Geochimiques, CRPG-CNRS, Universite de Lorraine, 15 rue Notre Dame des Pauvres, BP 20, 54501 Vandoeuvre les Nancy, France. ; Aix Marseille Universite, CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, 13388 Marseille, France. ; Institute for Astronomy, University of Hawaii, Honolulu, Hawaii 96822, USA. ; Universite de Toulouse-UPS-OMP-IRAP, 31400 Toulouse, France. ; CNRS-IRAP, 9 avenue du Colonel Roche, BP 44346, F-31028 Toulouse Cedex 4, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26511578" target="_blank"〉PubMed〈/a〉