ABSTRACT
The past few decades of observational studies have shown that the molecular content of interstellar space in our galaxy is far richer than ever previously imagined. Interstellar chemistry produces a wide variety of molecular species, ranging from diatomic species to fullerenes. Furthermore, most common organic functional groups are found in interstellar compounds, as represented by simple acids, aldehydes, ketones, amides, ethers, esters, and alcohols, as well as basic phosphorus-bearing molecules such as PO and CCP. However, the molecular material is not formed in isolation but is cycled from one phase of the interstellar medium to another, starting in dying stars, which eject chemical compounds into the diffuse clouds. These clouds collapse into denser objects and eventually solar systems. This cycling enables carbon enrichment from evolved stars to be preserved and seeds the organic chemistry of dense clouds and protoplanetary disks. Some of the pristine and partly processed interstellar molecular material is condensed onto surfaces that aggregate to solar system bodies, including comets and meteorites, which deliver the chemical compounds to planet surfaces. Given their widespread distribution in the galaxy, overwhelming abundances, and remarkable survival on transport through many harsh environments, interstellar molecules very likely play a role in pre-biotic chemistry.
