Comets carbon chemistry

Carbon based chemistry (organic chemistry) has thus been established to be of fundamental importance in interstellar molecular clouds. Similarly the observed composition of comets is dominated by carbon bearing molecules, and in the reducing atmospheres of Jupiter and Saturn the carbon chain molecules C2H2, CjH have been detected. 

Carbon compounds in the solar system can be traced in planetary atmospheres, on planetary surfaces, comets, asteroids, meteorites and in the interplanetary medium. Gas and solid state chemistry within the solar nebula was responsible for new organic material (49,50). Many organic compounds have been identified on outer solar system bodies, some of them originating in the surface ices through energetic processing (4). 

PAHs comprise a large percentage of the carbon found in interstellar space. They have even been observed in interstellar ice (Halley s comet, for example). It has been shown that ultraviolet irradiation of PAHs in ice produces aromatic ketones (Chapter 9), alcohols (Chapter 7), and other compounds, suggesting a role of PAHs in prebiotic chemistry (see A Word about Methane, Marsh Gas, and Miller s Experiment, page 60). 

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