Cometary materials: Progress toward understanding the composition in the outer solar nebula

A major objective of the workshop was to learn about the chemical compositi on, physical structure, and thermodynamic conditions of the outer parts of the solar nebula where comets formed. Here we sum up what we have learned f rom years of research about the molecular constituents of comet comae prima rily from in situ measurements of Comet 1P/Halley and remote sensing of Com ets 1P/Halley, Hale-Bopp (C/1995 O1), and Hyakutake (C/1995 B2). These thre e bright comets are presumably captured Oort cloud comets. We summarize the analyses of these data to predict the composition of comet nuclei and proj ect them further to the composition, structure, and thermodynamic condition s in the nebula. Near-future comet missions are directed toward less active short-period Jup iter-family comets. Thus, future analyses will afford a better understandin g of the diversity of these two major groups of comets and their respective regions of origin in the solar or presolar nebula. We conclude with recommendations for determining critical data needed to ai d in further analyses. Results of the workshop provide new guidelines and c onstraints for modeling the solar nebula.