Modeling the Chemistry of Protoplanetary Disks

Planet-forming disks around young stars exhibit a rich diversity in their chemical content, with observations over the past decade using the Atacama Large Millimeter Array and now the James Webb Space Telescope showing emission signatures of the complex physical, dynamical and chemical processes that occur en route to planet formation. Chemical evolution begins in the cold, interstellar cloud material where species condense onto growing dust particles. Material then falls on to a disk and may get heated during the star formation phase with some or all of the ices being lost. As disks form planets and ultimately disperse, their material is subject to radial and vertical transport processes, impacting the radiation environment and the physical state (vapor or condensed phase) of different chemical species. State-of-the-art models consider irradiation by Ultraviolet and X-ray photons, grain surface chemistry and particle-gas dynamical interactions in a framework that solves for gas and particle evolution with time. Chemical species in the vapor phase and in the condensed phase (as ices on dust particles) are explicitly tracked, with the goal of understanding how the organic inventory available to forming planets is transformed from the cloud to disk. Planet formation may itself result in changes in the bulk chemical composition in disks by preferentially locking C,N,O-bearing species depending on where in the disk planets form. I will summarize recent efforts toward modeling these complex processes as disks form from interstellar cloud material and later evolve, and the implications for the composition of planets and other small bodies that form within, including those in our own Solar System.