Composition of Early Planetary Atmospheres II: Coupled Dust and Chemical Evolution in Protoplanetary Disks

TL;DR

This study models the coupled dust and chemical evolution in protoplanetary disks to understand how planetary atmospheres' compositions, especially C/O and C/N ratios, relate to their formation environments and histories.

Contribution

It introduces a comprehensive model linking disk chemistry and dust evolution with planet formation, analyzing how initial disk mass influences atmospheric composition and planetary characteristics.

Findings

C/O ratios in planetary atmospheres closely match disk C/O ratios.

Nitrogen content varies with disk models and formation history.

Atmospheric NH₃ abundance encodes information about planet formation processes.

Abstract

We present the next step in a series of papers devoted to connecting the composition of the atmospheres of forming planets with the chemistry of their natal evolving protoplanetary disks. The model presented here computes the coupled chemical and dust evolution of the disk and the formation of three planets per disk model. Our three canonical planet traps produce a Jupiter near 1 AU, a Hot Jupiter and a Super-Earth. We study the dependency of the final orbital radius, mass, and atmospheric chemistry of planets forming in disk models with initial disk masses that vary by 0.02 $M_\odot$ above and below our fiducial model ($M_{disk,0} = 0.1 ~M_\odot$). We compute C/O and C/N for the atmospheres formed in our 3 models and find that C/O$_{\rm planet}\sim$ C/O$_{\rm disk}$, which does not vary strongly between different planets formed in our model. The nitrogen content of atmospheres can vary in planets that grow in different disk models. These differences are related to the formation history of the planet, the time and location that the planet accretes its atmosphere, and are encoded in the bulk abundance of NH$_3$. These results suggest that future observations of atmospheric NH$_3$ and an estimation of the planetary C/O and C/N can inform the formation history of particular planetary systems.