Clouds in Exoplanetary Atmospheres

TL;DR

This paper discusses the diversity of exoplanets and emphasizes the need for complex, physically rigorous models of exoplanet atmospheres, especially cloud formation, to better understand their properties and improve observational interpretations.

Contribution

It highlights the importance of developing fundamental, physics-based models of cloud formation and atmospheric processes for exoplanets, moving beyond solar system-inspired parameterizations.

Findings

Identification of key challenges in modeling exoplanet atmospheres.

Advocacy for physics-based cloud modeling applicable to diverse exoplanet conditions.

Emphasis on the role of models as virtual laboratories to complement observations.

Abstract

Today, we know ~4330 exoplanets orbiting their host stars in ~3200 planetary systems. The diversity of these exoplanets is large, and none of the known exoplanets is a twin to any of the solar system planets, nor is any of the known extrasolar planetary systems a twin of the solar system. Such diversity on many scales and structural levels requires fundamental theoretical approaches. Large efforts are underway to develop individual aspects of exoplanet sciences, like exoplanet atmospheres, cloud formation, disk chemistry, planet system dynamics, mantle convection, mass loss of planetary atmospheres. The following challenges need to be addressed in tandem with observational efforts. They provide the opportunity to progress our understanding of exoplanets and their atmospheres by exploring our models as virtual laboratories to fill gaps in observational data from different instruments and missions, and taken at different instances of times: Challenge a) Building complex models based on theoretical rigour that aim to understand the interactions of atmospheric processes, to treat cloud formation and its feedback onto the gas-phase chemistry and the energy budget of the planetary atmosphere moving away from solar-system inspired parameterisations. Challenge b) Enabling cloud modelling based on fundamental physio-chemical insights in order to be applicable to the large and unexplored chemical, radiative and thermodynamical parameter range of exoplanets in the universe. Challenge b) will be explored in this chapter of the book ExoFrontiers.