C/N/O Ratios and Ice Lines in Dynamical Protoplanetary Disks

Elizabeth S. Yunerman

Protoplanetary disk ice lines are known to shape a multitude of planet formation processes, especially in setting the elemental ratios from volatiles which are incorporated into forming planetary cores and atmospheres. Ice line locations in disks are determined by the assumed midplane temperature profile and the nature of major volatiles, but can also depend on the dynamics governing the motion of gas and solids. In a recent model, Price et al. (2021) demonstrated that the combination of disk thermal evolution, inward drift of small solids, and sublimation and re-condensation of CO around the CO ice line could increase the CO/H2O ice ratio-and therefore the solid C/O ratio-by an order of magnitude just beyond the CO ice line. In this work, we expand on the Price et al. (2021) model to 1) determine whether analogous enhancements and non-standard elemental ratios should be expected around other disk ice lines, and 2) introduce additional microphysical dynamical processes that may have an impact on the composition and transport of ice particles in a disk, and therefore on the disk C/N/O radial profile. We increase the model’s chemical library to include other relevant disk molecules (in particular CO2, CH4, N4, NH3, and NH4COOH), consider the importance of the Stokes drag regime, and evaluate a varying particle size distribution. I will present the key results of the expanded model, and discuss how they impact our understanding of planet formation at differing disk radii with a variety of compositions.