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M. J. Mumma (NASA-GSFC), M. A. DiSanti, N. Dello Russo (Catholic Univ. and NASA-GSFC), K. Magee-Sauer (Rowan University), T. W. Rettig (Notre Dame University), M. Fomenkova (Univ. Cal. San Diego)
Free-radicals are widely understood to be produced by dissociative processes in the cometary coma, but some "parent" species (e.g. CO) are released both directly from the nucleus and also from extended sources in the coma. It is necessary to separate the direct and distributed sources for a species before the composition of cometary ices and the properties of low-temperature refractories (e.g.) can be assessed. Moreover, the interpretation of large-beam measurements of cometary volatiles becomes highly dependent on model assumptions unless the relative contributions of native and distributed sources are known. Since the relative contributions of direct and distributed sources can change with heliocentric distance, the interpretation of changing production rates becomes doubly uncertain when both sources are present. Here, we discuss long slit infrared spectra of volatiles in comets Hyakutake and Hale-Bopp, and show how native and distributed sources have been separately identified. Implications for related observations and for their interpretation are discussed.