Mineral cloud and hydrocarbon haze particles in the atmosphere of the hot Jupiter JWST target WASP-43b
Ch. Helling, Yui Kawashima, V. Graham, Dominic Samra, K. L. Chubb, M. Min, L. B. F. M. Waters, Vivien Parmentier
Abstract
Context: Having a short orbital period and being tidally locked makes WASP-43b an ideal candidate for the James Webb Space Telescope (JWST) phase curve measurements. Phase curve observations of an entire orbit will enable the mapping of the atmospheric \nstructure across the planet, with different wavelengths of observation allowing different atmospheric depths to be seen. \nAims: We provide insight into the details of the clouds that may form on WASP-43b and their impact on the remaining gas phase, in \norder to prepare the forthcoming interpretation of the JWST and follow-up data. \nMethods: We follow a hierarchical modelling strategy. We utilise 3D GCM results as input for a kinetic, non-equilibrium model for \nmineral cloud particles and for a kinetic model to study a photochemically-driven hydrocarbon haze component. \nResults: Mineral condensation seeds form throughout the atmosphere of WASP-43b. This is in stark contrast to the ultra-hot Jupiters, \nsuch as WASP-18b and HAT-P-7b. The dayside is not cloud free but it is loaded with few yet large mineral cloud particles in addition to \nhydrocarbon haze particles of a comparable abundance. Photochemically driven hydrocarbon haze appears on the dayside, but it does \nnot contribute to the cloud formation on the nightside. The geometrical cloud extension differs across the globe due to the changing \nthermodynamic conditions. Day and night differ by 6000 km in pressure scale height. As reported for other planets, the C/O is not \nconstant throughout the atmosphere and varies between 0.74 and 0.3. The mean molecular weight is approximately constant in a H2- \ndominated WASP-43b atmosphere because of the moderate day/night-temperature differences compared to the super-hot Jupiters. \nConclusions: WASP-43b is expected to be fully covered in clouds which are not homogeneously distributed throughout the atmosphere. The dayside and the terminator clouds are a combination of mineral particles of locally varying size and composition as well \nas of hydrocarbon hazes. The optical depth of hydrocarbon hazes is considerably lower than that of mineral cloud particles such that a \nwavelength-dependent radius measurement of WASP-43b would be determined by the mineral cloud particles but not by hazes.