Spectroscopic Investigations of the Chemical Composition and Coma Morphology of Comets

Abstract:

Ground-based emission spectroscopy at optical wavelengths is important for understanding the chemical composition of comets. We have made spectroscopic observations of comets using both long-slit and integral-field unit spectrographs on the Harlan J. Smith telescope at the University of Texas McDonald Observatory in order to study radical species in cometary comae. We will discuss the techniques used to extract chemical abundances in comets from these data and show how the spatial distribution of the observed species and large-scale coma morphological features (e.g. jets or fans) are mapped and characterized. Analyses of data we have acquired for several comets to date will be presented that examine their chemical abundances, track the temporal evolution of coma morphology in relation to nuclear rotational behavior (where known), and gauge potential chemical heterogeneity of cometary nuclei. We will also place this work into broader context by comparing our results to existing large-sample photometric and spectroscopic surveys of comets, as well as comparing our results to those obtained during prior apparitions to determine whether these comets show any evolutionary changes in measured chemical abundances or sources of outgassing on their surfaces. This work has been funded by the NSF GK-12 STEM Fellowship program, NASA’s Planetary Astronomy and Planetary Atmospheres programs, and the Fund for Astrophysical Research, Inc.