C/O ratio as a Dimension for Characterizing Exoplanetary Atmospheres

Understand

Until recently, infrared observations of exoplanetary atmospheres have typically been interpreted using models that assumed solar elemental abundances.

• With the chemical composition fixed, attempts have been made to classify hot Jupiter atmospheres on the basis of stellar irradiation.
• However, recent observations have revealed deviations from predictions based on such classification schemes, and chemical compositions retrieved from some datasets have also indicated non-solar abundances.
• In hot hydrogen-dominated atmospheres, the C/O ratio critically influences the relative concentrations of several spectroscopically dominant molecules.