S18A0071abst
S18A0071
We propose to use NIRSPEC at Keck II to measure the chemical composition of comet 21P/Giacobini-Zinner (hereafter 21P/GZ), a short-period Jupiter-family comet. We will determine the chemical composition in this comet through a sensitive search for the following molecular species: H2O, CO, CH4, CH3OH, H2CO, C2H6, HCN, C2H2, NH3, and NH2. We emphasize that 21P/GZ is peculiar from the viewpoints of both volatiles and dust grains; (i) the comet is chemically peculiar as characterized by low C2/H2O and low NH2/H2O ratios based on optical spectroscopic measurements and (ii) the silicate grains in 21P/GZ were almost entirely in the crystalline phase (> 90% crystalline silicates), whereas other comets typically show βΌ 40 - 80% crystalline silicates. To date the chemistry of parent volatiles in 21P/GZ has been only partially characterized at high-resolution infrared spectroscopy. Complete characterization of such a peculiar comet is essentially important to reveal chemical diversity of cometary volatiles related to formation chemistry and evolution of cometary volatiles. Our requested observations will provide the first complete measure of parent volatiles in this proto-typical carbon-chain depleted comet, for comparison with abundances of its photo-dissociation products.
This document was translated from LATEX by HEVEA.