It is becoming increasingly clear, based on a combination of observational, theoretical, and laboratory studies, that the interstellar medium (ISM) is not chemically “inert.” Instead, it contains a variety of distinct environments in which chemical synthesis and alteration are constantly occurring under the aegis of a number of different processes. The result of these different processes is an interstellar medium rich in chemical diversity. The discussion found here will concentrate on those materials and molecular species built from the elements C, H, O, and N, with particular emphasis on those compounds that may be of prebiotic interest. Furthermore, there is excellent evidence that the products of interstellar chemistry are not restricted solely to the ISM, but that some fraction of these materials survive the transition from interstellar dense clouds to planetary surfaces when new stars and planets form in these clouds. This raises the interesting possibility that molecules created in the interstellar medium may play a role in the origin and evolution of life on planetary surfaces.

Introduction

A variety of organic and volatile compounds are now known or suspected to exist in a number of different space environments including stellar outflows, the diffuse interstellar medium, dense molecular clouds, and protostellar nebulae.