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Originally published in Science Express on 13 July 2006
Science 4 August 2006:
Vol. 313. no. 5787, pp. 635 - 640
DOI: 10.1126/science.1124694
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Research Articles

Spitzer Spectral Observations of the Deep Impact Ejecta

C. M. Lisse,1,2* J. VanCleve,3 A. C. Adams,3 M. F. A'Hearn,2 Y. R. Fernández,4 T. L. Farnham,2 L. Armus,5 C. J. Grillmair,5 J. Ingalls,5 M. J. S. Belton,6 O. Groussin,2 L. A. McFadden,2 K. J. Meech,7 P. H. Schultz,8 B. C. Clark,9 L. M. Feaga,2 J. M. Sunshine2

Spitzer Space Telescope imaging spectrometer observations of comet 9P/Tempel 1 during the Deep Impact encounter returned detailed, highly structured, 5- to 35-micrometer spectra of the ejecta. Emission signatures due to amorphous and crystalline silicates, amorphous carbon, carbonates, phyllosilicates, polycyclic aromatic hydrocarbons, water gas and ice, and sulfides were found. Good agreement is seen between the ejecta spectra and the material emitted from comet C/1995 O1 (Hale-Bopp) and the circumstellar material around the young stellar object HD100546. The atomic abundance of the observed material is consistent with solar and C1 chondritic abundances, and the dust-to-gas ratio was determined to be greater than or equal to 1.3. The presence of the observed mix of materials requires efficient methods of annealing amorphous silicates and mixing of high- and low-temperature phases over large distances in the early protosolar nebula.

1 Planetary Exploration Group, Space Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, USA.
2 Department of Astronomy, University of Maryland, CSS 2341, College Park, MD 20742, USA.
3 Ball Aerospace and Technologies Corporation, 1600 Commerce Street, Boulder, CO 80306, USA.
4 Department of Physics, University of Central Florida, Post Office Box 162385, Orlando, FL 32816–2385, USA.
5 Spitzer Space Science Center, California Institute of Technology, Pasadena, CA 91125, USA.
6 Belton Space Exploration Initiatives, 430 Randolph Way, Tucson, AZ, 85716, USA.
7 Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA.
8 Department of Geological Sciences, Brown University, Providence, RI 02912–1846, USA.
9 Space Exploration Systems, Lockheed Martin, Denver, CO 80201, USA.

* To whom correspondence should be addressed.

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