Protoplanetary Disk Chemistry

Abstract

Planets form in disks of gas and dust around young stars. The disk molecular reservoirs and their chemical evolution affect all aspects of planet formation, from the coagulation of dust grains into pebbles to the elemental and molecular compositions of the mature planet. Disk chemistry also enables unique probes of disk structures and dynamics, including those directly linked to ongoing planet formation. We review the protoplanetary disk chemistry of the volatile elements H, O, C, N, S, and P; the associated observational and theoretical methods; and the links between disk and planet chemical compositions. Three takeaways from this review are: ▪ The disk chemical composition, including the organic reservoirs, is set by both inheritance and in situ chemistry. ▪ Disk gas and solid O/C/N/H elemental ratios often deviate from stellar values due to a combination of condensation of molecular carriers, chemistry, and dynamics. ▪ Chemical, physical, and dynamical processes in disks are closely linked, which complicates disk chemistry modeling, but they also present an opportunity to develop chemical probes of different aspects of disk evolution and planet formation. Expected final online publication date for the Annual Review of Astronomy and Astrophysics, Volume 61 is August 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Thermal Structure Determines Kinematics: Vertical Shear Instability in Stellar Irradiated Protoplanetary Disks

“…While static disk models cover more complete chemical networks, studies considering dynamical effects (e.g., Aikawa & Herbst 1999;Semenov & Wiebe 2011;Furuya et al 2013;Furuya & Aikawa 2014;Price et al 2020;Bergner & Ciesla 2021;Van Clepper et al 2022) by incorporating radial and/or vertical gas/dust mixing often reveal different chemical distributions compared to static models. These dynamic models may provide a better explanation for observations (see reviews by Krijt et al 2022 andÖberg et al 2023, andreferences therein). We anticipate that, by accounting for advection and turbulent diffusion due to a specific thermal structure, the chemical distribution can be more accurately predicted.…”