Reactions of aromatics in space and connections to the carbon chemistry of Solar System materials

Polycyclic aromatic hydrocarbons (PAHs) and related aromatic materials are thought to be the most abudant class of organic carbon in the universe, being present in virtually all phases of the ISM, and abundant in carbonaceous meteorites and asteroid and comet dust. The basic PAH skeleton is proposed to have formed in outflows of carbon rich stars, and isotopic measurements of extraterrestrial graphitic carbon is consistent with this notion. However, functionalized aromatics bearing oxygen atoms, aliphatic domains, and deuterium enrichments have been extracted from meteorites and more recently been measured in IDPs and Stardust retuned comet samples. Exposure of remnant circumstellar PAHs to energetic processing at low temperature in the presense of H₂O is the most parsimonious explanation for these observations.