Name: David E. Harker

Institution: University of California, San Diego

e-mail: dharker(no-spam)ucsd.edu

Partner Contry: USA

Science Meeting: Yes

User Meeting: Yes

NGO Staff Meeting: None Selected

Presentation: Yes

Format: Oral

Title: Mid-Infrared Observations of Comet 9P/Tempel 1 at Deep Impact

Co-author: Charles E. Woodward

Co-authors' Institutions: University of Minnesota NASA Ames Research Center Gemini Observatory

Abstract

e present mid-infrared spectra and images from the GEMINI-N ( MICHELLE) observational campaign of comet 9P/Tempel 1 before, during, and after its encounter with Deep Impact. The Gemini-N spectra (taken at a ~7 min cadence) are the only mid-IR data to be obtained during the impact event. Before impact (3 July 2005 UT), and more than 21~hours after impact (5, 16, and 28 July 2005 UT), the comet dust grains were composed mostly of amorphous olivine, and were relatively large (peak of the grain size distribution a_p = 0.7 - 1.5 micron). For the night of impact, we find small dust grains (~0.2 micron) of a diverse mineralogy (amorphous olivine, amorphous pyroxene, amorphous carbon, and crystalline olivine) populating the ejecta. The submicron sized dust grains move faster than the other, larger grains (~0.7 micron), with amorphous olivine and amorphous carbon traveling at a similar speed, and amorphous pyroxene and crystalline olivine traveling at another, similar speed. Sinc! e the mineral species are traveling at different speeds, we conclude that the different minerals did not originate from the same grain aggregate destroyed by the impact, but instead arise from different area of the nucleus.