Comets, interstellar molecules, and the origin of life.

This review considers two quite distinct subjects: comets, and the relative abundance of molecules in the gas phase in interstellar clouds. The justification for a joint treatment lies in the possibility that comets may consist of a frozen matrix of interstellar volatiles and grains, formed during the early stages of the collapse of the molecular cloud which ultimately produced the Sun and planets. These topics may in turn be related to the origin of life, as the distribution of biologically significant molecules in space bears on the likelihood of chemical evolution throughout the universe, and, more specifically, comets might be a source of planetary volatiles, possibly including complex organic molecules.