The atmospheric influence, size and possible asteroidal nature of the July 2009 Jupiter impactor G.S. Orton a,⇑ , L.N. Fletcher b , C.M. Lisse c , P.W. Chodas a , A. Cheng c , P.A. Yanamandra-Fisher a , K.H. Baines a , B.M. Fisher a , A. Wesley d , S. Perez-Hoyos e , I. de Pater f , H.B. Hammel g , M.L. Edwards h , A.P. Ingersoll i , O. Mousis j , F. Marchis f,k , W. Golisch l , A. Sanchez-Lavega e , A.A. Simon-Miller m , R. Hueso e , T.W. Momary a , Z. Greene n , N. Reshetnikov o , E. Otto p , G. Villar q , S. Lai r , M.H. Wong s a Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA b Oxford University Atmospheric, Oceanic and Planetary Physics, Parks Rd., Oxford OX1 3PU, UK c Johns Hopkins University, Applied Physics Laboratory, Laurel, MD 20723, USA d Acquerra Pty. Ltd., 82 Merryville Drive, Murrumbateman, NSW, Australia e ETS de Ingeniería, Universidad del Pais Vasco, Alameda Urquijo s/n, 48013 Bilbao, Spain f University of California, Berkeley Astronomy Dept., 601 Campbell Hall, Berkeley, CA 94720-3411, USA g Space Science Institute, 72 Sarah Bishop Rd., Ridgefield, CT 06877, USA h Gemini Observatory, Colina El Pino via s/n, Casiilla 603, La Serena, Chile i Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA j Observatoire de Besançon, Institut UTINAM, UMR/CNRS 6213, 41 bis Avenue de l’Observatoire, BP 1615, 25010 Besançon Cedex, France k SETI Institute, 515 N. Whisman Rd., Mountain View, CA 94043, USA l Institute for Astronomy, University of Hawaii 640 N. A’ohoku Place, Hilo, HI 96720, USA m NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA n University of California, Los Angeles, Department of Physics and Astronomy, Los Angeles, CA 90095-1547, USA o Harvard University, Cambridge, MA 02138, USA p Ohio State University, 0620 Taylor Tower, 50 Curl Dr. Columbus, OH 43210, USA q California State University, Pomona, 3801 West Temple Avenue, Pomona, CA 91768-2557, USA r California Institute of Technology, 1201 E. California Blvd., Pasadena, CA 91125, USA s Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218, USA article info Article history: Received 19 February 2010 Revised 18 October 2010 Accepted 19 October 2010 Available online 27 October 2010 Keywords: Jupiter Impact processes Infrared observations Comets Asteroids abstract Near-infrared and mid-infrared observations of the site of the 2009 July 19 impact of an unknown object with Jupiter were obtained within days of the event. The observations were used to assess the properties of a particulate debris field, elevated temperatures, and the extent of ammonia gas redistributed from the troposphere into Jupiter’s stratosphere. The impact strongly influenced the atmosphere in a central region, as well as having weaker effects in a separate field to its west, similar to the Comet Shoe- maker-Levy 9 (SL9) impact sites in 1994. Temperatures were elevated by as much as 6 K at pressures of about 50–70 mbar in Jupiter’s lower stratosphere near the center of the impact site, but no changes above the noise level (1 K) were observed in the upper stratosphere at atmospheric pressures less than 1 mbar. The impact transported at least 2  10 15 g of gas from the troposphere to the stratosphere, an amount less than derived for the SL9 C fragment impact. From thermal heating and mass-transport considerations, the diameter of the impactor was roughly in the range of 200–500 m, assuming a mean density of 2.5 g/cm 3 . Models with temperature perturbations and ammonia redistribution alone are unable to fit the observed thermal emission; non-gray emission from particulate emission is needed. Mid-infrared spectroscopy of material delivered by the impacting body implies that, in addition to a sil- icate component, it contains a strong signature that is consistent with silica, distinguishing it from SL9, which contained no evidence for silica. Because no comet has a significant abundance of silica, this result is more consistent with a ‘‘rocky’’ or ‘‘asteroidal’’ origin for the impactor than an ‘‘icy’’ or ‘‘cometary’’ one. This is surprising because the only objects generally considered likely to collide with Jupiter and its sat- ellites are Jupiter-Family Comets, whose populations appear to be orders of magnitude larger than the Jupiter-encountering asteroids. Nonetheless, our conclusion that there is good evidence for at least a major asteroidal component of the impactor composition is also consistent both with constraints on the geometry of the impactor and with results of contemporaneous Hubble Space Telescope observations. 0019-1035/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.icarus.2010.10.010 ⇑ Corresponding author. Fax: +1 818 393 4619. E-mail address: go@scn.jpl.nasa.gov (G.S. Orton). Icarus 211 (2011) 587–602 Contents lists available at ScienceDirect Icarus journal homepage: www.elsevier.com/locate/icarus