The composition of cometary ices as inferred from measured production rates of volatiles

Viac o knihe

This work characterizes the chemical and physical properties of comets using high-dispersion mid-infrared spectroscopy (2 to 5 µm). Inorganic and organic parent molecules were detected in comets 8P/Tuttle and C/2007 W1 (Boattini) using CRIRES at the ESO Very Large Telescope. A model for the v1 vibrational transition of the HCN molecule in cometary comae was developed, along with a review of the mathematical steps needed to analyze emission line fluxes for chemical composition. Observed in January 2008, 8P/Tuttle is a Halley-type comet with a 13.6-year orbital period and an inclination of about 55 degrees. Its chemical composition shows depletion in CO, CH4, C2H6, and HCN, but enrichment in CH3OH, suggesting it may consist of two different cometesimals or belong to a previously unobserved taxonomical class. The HCN and CN production rates were compared, revealing that CN production was higher, indicating HCN is not the sole parent molecule for the CN radical. Comet C/2007 W1, observed in May and July 2008, is rich in organics and volatile materials, with consistent HCN and CN production rates. The study also explored potential correlations between dynamical and chemical classes across different comets, but found no clear relationships.