The Chemical Evolution of Protoplanetary Disks

In this review we re-evaluate our observational and theoretical understanding of the chemical evolution of protoplanetary disks. We discuss how improved observational capabilities have enabled the detection of numerous molecules exposing an active disk chemistry that appears to be in disequilibrium. We outline the primary facets of static and dynamical theoretical chemical models. Such models have demonstrated that the observed disk chemistry arises from warm surface layers that are irradiated by X-ray and FUV emission from the central accreting star. Key emphasis is placed on reviewing areas where disk chemistry and physics are linked: including the deuterium chemistry, gas temperature structure, disk viscous evolution (mixing), ionization fraction, and the beginnings of planet formation.