S21B0064

We propose to use NIRSPEC at Keck II to measure the chemical composition of comet 67P/Churyumov-Gerasimenko (hereafter 67P/CG), the target of the ESA mission Rosetta. Determining the composition and structure of cometary nuclei is essential to understanding the formation and evolution of volatile materials within our solar system. This upcoming favorable apparition of 67P/CG enables a study of the outgassing of H₂O, CH₃OH, C₂H₆, H₂CO, C₂H₂, HCN, and NH₃ using near-infrared (NIR) spectroscopy. The volatile composition and outgassing behavior of 67P/CG are known with unprecedented detail through two years of in-situ measurements by Rosetta. The ground-based NIR observations proposed here are the first opportunity to put the detailed compositional measurements of this mission target into the context of the many chemically-diverse comets studied using ground-based NIR spectroscopy. This allows a critical test of how volatile comet composition obtained by remote sensing at global spatial scales relates to the incredibly detailed "ground truth" data obtained by Rosetta. Our proposal will enable insights about 67P/CG from Rosetta to be extended to the overall comet population providing additional insights into the formation and evolution of cometary ices.

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