Since the dawn of time, mankind has wondered about the formation and volatile composition of planet atmospheres. Connecting the observed composition of exoplanets to their formation sites often involves comparing the observed planetary atmospheric carbon-to-oxygen (C/O) ratio to a disk midplane model with a fixed chemical composition. In this scenario, chemistry evolution in the midplane prior to and during the planet formation era is not considered. The C/O ratios of gas and ice in disk midplane are simply defined by volatile ice-lines in a midplane of fixed chemical composition. However, kinetic chemical evolution during the lifetime of the gaseous disk can change the relative abundances of volatile species, thus altering the C/O ratios of planetary building blocks. In my chemical evolution models, I utilize a large network of gas-phase, grain-surface and gas-grain interaction reactions, thus providing a comprehensive treatment of chemistry. In my talk, I will show how chemical evolution can modify disk midplane chemistry, and how this affects the C/O ratio of giant planet-forming material. I will argue that midplane chemical evolution needs to be addressed when predicting the chemical makeup of planets and their atmospheres.

From disk midplane to planet atmosphere: The chemical link

ACS Spring Meeting 2021

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