Disequilibrium chemistry in WASP-43b seen by our 3D Global Circulation Model

The different gas components in the atmosphere of exoplanets are exposed to different temperatures and pressure conditions that shape the spectral information captured by the telescopes. The development of robust theoretical tools to help unveiling the atmospheric composition of exoplanets will play an important role in the characterization of exoplanet atmospheres and in the interpretation of the observational data.

THOR became the first model in the exoplanet community to be able to study how CO, CO2, H2O and CH4 are dynamically distributed across the atmosphere of a hot Jupiter planet [1]. To be able to achieve this goal we have implemented a simple method called relaxation method developed in [2], which captures the main results of a complex chemical network. Different chemical species in the atmosphere interact under a very complex chemical network that controls the different abundances in the atmosphere. However, there are several processes that can disturb this balance, such as the atmospheric dynamics. In our work, the chemistry in the atmosphere of WASP-43b (a hot Jupiter) is determined by the balance between chemical reactions and atmospheric dynamics.

In the figure below, we show an example of how the different molecules are distributed across the atmosphere at a pressure level where the equatorial jet has a large impact.

Distribution of CH4, CO, H2O, and CO2 at 10 mbar as a function of latitude and longitude from the simulations with different G and C/O. G is the greenhouse parameter. If G is equal to 2, the temperature in the upper atmosphere increases with altitude (thermal inversion). The colours represent the volume mixing ratio of the different chemical species. All the results shown in this figure were averaged over the last 100 days of the simulations.

See our article to learn more about other results on how the atmospheric mixing influences the chemistry and spectral signatures of exoplanet atmospheres.

[1] – Mendonca J., Tsai S., Malik M., Grimm S., Heng K.,  ‘Three-Dimensional Circulation Driving Chemical Disequilibrium in Wasp-43b’, 2018, Volume 869, Issue 2, The Astrophysical Journal [Link]

[2] – 9. Tsai S., Kitzmann D., Lyons J., Mendonca J.,  Grimm S., Heng K., ‘Towards Consistent Modeling of Atmospheric Chemistry and Dynamics in Exoplanets: Validation and Generalization of Chemical Relaxation Method’, 2018, Volume 862, Issue 1, The Astrophysical Journal [Link]

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