FUV Observations of 46P/Wirtanen’s Inner Coma

Comet 46P/Wirtanen’s close approach in 2018 brought it within 0.077 AU (12 million kilometers) of Earth on December 16th, 2018. This encounter presented the opportunity to directly study the inner coma (<1000 km from the nucleus) of a comet, a region often difficult to measure for comets due to their distance from the Earth. The Hubble Space Telescope’s Cosmic Origins Spectrograph was used to acquire far ultraviolet (FUV) spectra of the comet from January 9 to 20, 2019 to search for atomic and molecular transitions of the common cometary dissociative products H, C, O, S, and CO. Observations of 46P/Wirtanen were taken with three goals in mind: 1. Identify the dominant physical processes of the inner coma and search for evidence of dissociative electron impact emission, 2. Find the relative abundances of H₂O, CO2, and CO with emission modeling of dissociation products and, 3. Look for the emission signature of the supervolatile O2 observed in situ in the coma of 67P/Churyumov-Gerasimenko and 1P/Halley by the Rosetta and Giotto missions. In this talk we will present results and analysis in these three categories, describe the atomic abundances observed, provide column densities of parent neutrals derived from the FUV emissions, compare the results to observations from the Alice instrument on board Rosetta and previous UV observations of 46P, and discuss the implications for remote observations of the inner comae of comets in the future. observations of the inner comae of comets in the future.