ar X iv : a st ro - p h / 06 07 18 5 v 1 1 0 Ju l 2 00 6 Carbon Monoxide in Comet 9 P / Tempel 1 before and after the Deep Impact Encounter

One of the goals of the Hubble Space Telescope program to observe periodic comet 9P/Tempel 1 in conjunction with NASA’s Deep Impact mission was to study the generation and evolution of the gaseous coma resulting from the impact. For this purpose, the Solar Blind Channel of the Advanced Camera for Surveys was used with the F140LP filter which is sensitive primarily to the ultraviolet emission (≥ 1400Å) from the CO Fourth Positive system. Following the impact we detected an increase in brightness, which if all due to CO corresponds to 1.5×10 molecules or a mass of 6.6×10 kg, an amount that would normally be produced by 7–10 hours of quiescent outgassing from the comet. This number is ≤10% of the number of water molecules excavated, and suggests that the volatile content of the material excavated by the impact did not differ significantly from the surface or near sub-surface material responsible for the quiescent outgassing of the comet. Subject headings: comets: individual (9P/Tempel 1) — ultraviolet: solar system Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS 5-26555. Department of Physics and Astronomy, The Johns Hopkins University, Charles and 34th Streets, Baltimore, MD 21218, [email protected], [email protected], [email protected] Space Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723-6099, [email protected] Department of Astronomy, University of Maryland, College Park MD 20742-2421, [email protected] Belton Space Exploration Initiatives, Tucson, AZ 85716, [email protected] University of Hawaii, Institute for Astronomy and NASA Astrobiology Institute, 2680 Woodlawn Drive, Honolulu, HI 96822, [email protected]