Characterization of Gas Production in Comets: Establishing a Link Between Coma Composition and Volatile Composition of the Nucleus

Adam McKay

Comets are relics left over from the solar system's formation. Due to spending most of their lives far from the Sun, they have undergone very little thermal evolution over their lifetimes. This results in a near pristine composition, which reflects that of the protosolar nebula from which the comet formed. Yet direct observations of cometary nuclei are very rare. In most cases, we must observe the coma of the comet that surrounds the nucleus and from those observations infer properties of the nucleus. However, the coma is subject to many chemical and physical processes that alter its composition. Therefore the composition of the coma doesn't exactly reflect that of the nucleus. These processes must be understood in order to extrapolate nuclear composition from that of the coma. For this project I will observe two comets, 103P/ Hartley and C/2009 P1 Garradd, over a long temporal baseline using the ARCES echelle spectrometer mounted on the 3.5-m telescope at Apache Point Observatory. These observations provide data on gaseous species present in the coma, such as CN and C2. Supplementary observations of these comets using IRTF, Spitzer, and KECK will be proposed. Analysis of these observations will result in a characterization of the gas production in these comets over the course of an apparition. This characterization will improve our understanding of how coma composition relates to that of the nucleus.