More than two dozen primary volatiles in comets are now measured by ground-based infrared and millimeter spectroscopy, and several more from space platforms. Cometary water (H2O) was first detected in December 1985 using infrared spectroscopy from NASA’s Kuiper Airborne Observatory, and again in March 1986 with the KAO and (in situ) via infrared spectra from Vega 1 and in mass spectra from Giotto. The KAO results punctuated and validated a long effort (since 1972) to develop the concepts and methodology for infrared vibrational sensing of cometary parent volatiles, and marked the onset of 30 years of continuing advances that now permit simultaneous measurement of many primary volatiles using ground-based astronomical facilities. With more than 30 comets now studied in detail, the infrared database has permitted an emerging cometary taxonomy based on primary volatile composition. Similar advances in rotational spectroscopy began in 1985 (HCN) and extend now to detections of many CHONS species, including sulfides, amides, amines, acohols, aldehydes, and so on. The combination has revolutionized our understanding of these primitive bodies from the early planetary system, and of processes linking them to the protoplanetary disk and to the natal interstellar cloud core (Mumma and Charnley ARAA 2011). I will present aspects of the emerging taxonomy for comets based on composition, and compare them with insights obtained from Rosetta, Deep Impact/EPOXi, and Giotto.

Chemical and isotopic diversity of cometary volatiles: A window on evolutionary processes from the interstellar medium to icy planetesimals

252nd National Meeting (2016)

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