Work

Dynamics and Disequilibrium Carbon Chemistry in Hot Jupiter Atmospheres, with Application to HD 209458b

Year: 2006

Type: article

Abstract: Chemical equilibrium considerations suggest that, assuming solar elemental abundances, carbon on HD 209458b is sequestered primarily as carbon monoxide (CO) and methane (CH 4 ). The relative mole fractions of CO(g) and CH 4 (g) in chemical equilibrium are expected to vary greatly according to variations in local temperature and pressure. We show, however, that in the p = 1-1000 mbar range, chemical equilibrium does not hold. To explore disequilibrium effects, we couple the chemical kinetics of CO and CH 4 to a three-dimensional numerical model of HD 209458b's atmospheric circulation. These simulations show that vigorous dynamics caused by uneven heating of this tidally locked planet homogenize the CO and CH 4 concentrations at p < 1 bar, even in the presence of lateral temperature variations of ~500-1000 K. In the 1-1000 mbar pressure range we find that over 98% of the carbon is in CO. This is true even in cool regions where CH 4 is much more stable thermodynamically. Our work shows, furthermore, that planets 300-500 K cooler than HD 209458b can also have abundant CO in their upper layers due to disequilibrium effects. We demonstrate several interesting observational consequences of these results.

Source: The Astrophysical Journal

DOI: 10.1086/506312

Authors: Curtis S. Cooper, Adam P. Showman

Institution: University of Arizona

Language: English

Topic: Stellar, planetary, and galactic studies

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

SDG: Climate action

Open Access status: bronze

Funders: National Science Foundation, National Aeronautics and Space Administration