¹Schmitz, B.,²Farley, K.A.,³Goderis, S.,^4,5Heck, P.R.,⁶Bergström, S.M.,¹Boschi, S.,
⁷Claeys, P.,⁸Debaille, V.,^9,10Dronov, A.,¹¹van Ginneken, M.,¹²Harper, D.A.T.,¹Iqbal, F.,¹ Friberg, J.,^13,14Liao, S.,¹Martin, E.,^15,16 Meier, M.M.M.,¹⁷Peucker-Ehrenbrink, B.,¹⁷Soens, B.,¹⁵Wieler, R.,¹Terfelt, F.
Science Advances 5, eaax4184 Link to Article [DOI: 10.1126/sciadv.aax4184]
¹Astrogeobiology Laboratory, Department of Physics, Lund University, Lund, Sweden
²Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, United States
³Department of Chemistry, Vrije Universiteit Brussel, Brussels, Belgium
⁴Robert A. Pritzker Center for Meteoritics and Polar Studies, Field Museum of Natural History, Chicago, IL, United States
⁵Department of the Geophysical Sciences, University of Chicago, Chicago, IL, United States
⁶School of Earth Sciences, Ohio State University, Columbus, OH, United States
⁷Analytical, Environmental, and Geo-Chemistry, Vrije Universiteit Brussel, Brussels, Belgium
⁸Laboratoire G-Time, Université Libre de Bruxelles, Brussels, Belgium
⁹Geological Institute, Russian Academy of Sciences, Moscow, Russian Federation
¹⁰Institute of Geology and Oil and Gas Technologies, Kazan (Volga Region) Federal University, Kazan, Russian Federation
¹¹Royal Belgian Institute of Natural Sciences, Brussels, Belgium
¹²Department of Earth Sciences, Durham University, Durham, United Kingdom
¹³Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, China
¹⁴CAS Center for Excellence in Comparative Planetology, Hefei, China
¹⁵Department of Earth Sciences, ETH Zürich, Zürich, Switzerland
¹⁶Naturmuseum St. Gallen, St. Gallen, Switzerland
¹⁷Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, United States

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¹Takafumi Ootsubo,^2,3Hideyo Kawakita,²Yoshiharu Shinnaka,⁴Jun-ichi Watanabe,⁵Mitsuhiko Honda
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2019.113450]
¹Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1, Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210, Japan
²Laboratory of Infrared High-resolution Spectroscopy (LiH), Koyama Astronomical Observatory, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, Japan
³Department of Astrophysics and Atmospheric Sciences, Faculty of Science, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, Japan
⁴Public Relation Center, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
⁵Faculty of Biosphere-Geosphere Science Department of Biosphere-Geosphere Science, Okayama University of Science, 1-1 Ridaicho, Kita-ku, Okayama-shi 700-0005, Japan
Copyright Elsevier

Comet 21P/Giacobini-Zinner (hereafter, comet 21P/G-Z) is a Jupiter-family comet and a parent comet of the October Draconids meteor shower. If meteoroids originating from a Jupiter-family comet contain complex organic molecules, such as amino acids, they are essential pieces of the puzzle regarding the origin of life on Earth. We observed comet 21P/G-Z in the mid-infrared wavelength region using the Cooled Mid-infrared Camera and Spectrometer (COMICS) on the 8.2 m Subaru Telescope on UT 2005 July 5. Here, we report the unidentified infrared (UIR) emission features of comet 21P/G-Z, which are likely due to complex organic molecules (both aliphatic and aromatic hydrocarbons), and the thermal emission from amorphous/crystalline silicates and amorphous carbon grains in its mid-infrared low-resolution spectrum. The UIR features at ~8.2 μm, ~8.5 μm, and ~11.2 μm found in the spectrum of comet 21P/G-Z could be attributed to polycyclic aromatic hydrocarbons (or hydrogenated amorphous carbons) contaminated by N- or O-atoms, although part of the feature at ~11.2 μm comes from crystalline olivine. The other feature at ~9.2 μm might originate from aliphatic hydrocarbons. Comet 21P/G-Z is enriched in complex organic molecules. Considering that the derived mass fraction of crystalline silicates in comet 21P/G-Z is typical of comets, we propose that the comet originated from a circumplanetary disk of giant planets (similar to Jupiter and Saturn) where was warmer than the typical comet-forming region (5–30 au from the Sun) and was suitable for the formation of complex organic molecules. Comets from circumplanetary disks might be enriched in complex organic molecules, such as comet 21P/G-Z, and may have provided pre-biotic molecules to ancient Earth by direct impact or meteor showers.