Mineral cloud and hydrocarbon haze particles in the atmosphere of the hot Jupiter JWST target WASP-43b

TL;DR

This study models mineral cloud and hydrocarbon haze formation in WASP-43b's atmosphere, revealing complex cloud structures and composition variations crucial for interpreting upcoming JWST observations.

Contribution

It introduces a combined 3D GCM and kinetic modeling approach to characterize mineral clouds and hydrocarbon hazes on WASP-43b, highlighting their spatial distribution and properties.

Findings

Mineral clouds form throughout WASP-43b's atmosphere, contrasting with ultra-hot Jupiters.

Dayside has large mineral cloud particles and hydrocarbon hazes; nightside has fewer clouds.

Clouds are unevenly distributed, affecting observational signatures.

Abstract

Having a short orbital period and being tidally locked makes WASP-43b an ideal candidate for JWST observations. Phase curve observations of an entire orbit will enable the mapping of the atmospheric structure across the planet, with different wavelengths of observation allowing different atmospheric depths to be seen. We provide insight into the details of the clouds that may form on WASP-43b in order to prepare the forthcoming interpretation of the JWST and follow-up data. We utilize 3D GCM results as input for a kinetic, non-equilibrium model for mineral cloud particles, and for a kinetic model to study a photochemicaly-driven hydrocarbon haze component. Mineral condensation seeds form throughout the atmosphere of WASP-43b. This is in stark contrast to the ultra-hot Jupiters, like WASP-18b and HAT-P-7b. The dayside is loaded with few but large mineral cloud particles in addition to hydrocarbon haze particles of comparable abundance. Photochemically driven hydrocarbon haze appears on the dayside, but does not contribute to the cloud formation on the nightside. The geometrical cloud extension differs across the globe due to the changing thermodynamic conditions. Day and night differ by 6000km in pressure scale height. As reported for other planets, the C/O is not constant throughout the atmosphere. The mean molecular weight is approximately constant in a H2-dominated WASP-43b. WASP-43b is expected to be fully covered in clouds which are not homogeneously distributed throughout the atmosphere. The dayside and the terminator clouds will be a combination of mineral particles of locally varying size and composition, and of hydrocarbon hazes. The optical depth of hydrocarbon hazes is considerably lower than that of mineral cloud particles such that a wavelength-dependent radius measurement of WASP-43b would be determined by the mineral cloud particles but not by hazes.