Comet chemistry Halley

Flaeberli R M, Altwegg K, Balsiger FI and Geiss J 1995 Physics and chemistry of ions in the pile-up region of comet P/Halley Astron. Astrophys. 297 881-91... 

In fact the method may be strong in getting information on neutrons in comets, and in fact at our laboratory a mass spectrometer probe for the cometary mission of Halley s comet is prepared. But the scenario is a little bit different. Of course the gas tail of the comet has a very complex chemistry and you have gradients in concentrations and change in direction with the radiation field, that the ultimate goal would be to trace back the so-called OH. In order to get these, of course you have to translate or to imravel the entire chemistry — you measure a gas constituent which was produced by possibly not very well known processes. You have to evaporate first the material from the comet, then it is exposed to the UV radiation field of the sun, it s processed photo-chemically, it may undergo some reactions, so that would be very difficult. But there is a chance to get some information. 

Schulze H., Kissel J., and Jessberger E. K. (1997) Chemistry and mineralogy of Comet Halley s dust. In From Stardust to Planetesimals, ASP Conf. Ser. 122, 397p. 

Mendeleev s insight was a significant contribution to the development of chemistry. He showed that the properties of the elements repeat in an orderly way from row to row of the table. This repeated pattern is an example of periodicity in the properties of elements. Periodicity is the tendency to recur at regular intervals— like the appearance of Halley s comet every 76 years. 

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). 

Ireland TR (1995) Ion microprobe mass spectrometry. In Hyman M and Rowe M (eds) Techniques and Applications in Cosmochemistry, Geochemistry and Geochronology in Advances in Analytical Chemistry, Volume II, pp 51-118. Greenwich (UK) JAI Press. Krankowsky D and Eberhardt P (1990). In Mason JW and Horwood E (eds) Comet Halley Investigations, Results and Interpretations, Volume 1, pp. 273-296. New York Simon and Schuster. 

Recent infrared observations with the ISO satellite have detected fine structure in several of the bands, which indicates variable PAH composition throughout the medium. However, it is too early to begin identifying any of the particular species. These species have been detected in the IR emission from the comma of comet Halley as well, and it appears that in at least some environments, the chemistry required to produce the PAHs is sufficiently efficient that large abundances can be achieved. It has been suggested that fullerenes (such as Ceo) are responsible for some of the small grain population, but the spectral signatures— particularly in the visible and ultraviolet— have yet to be seen. 

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