Dust Clouds in Exoplanetary Atmospheres: A Laboratory View

• Applicants: Professor Dr. Falko Langenhorst; Dr. Alexey Potapov
• Subject Area: Astrophysics and Astronomy ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 567624163

The study of the structure, composition, and formation history of exoplanets and physical-chemical processes taking place in their atmospheres and interiors is one of the most intriguing and quickly developing frontiers in astronomy, astrophysics, and astrochemistry. Evidence to date shows that clouds and hazes are a common phenomenon in extrasolar planetary atmospheres. They play a crucial role in the temperature and atmospheric dynamics of planets and have a major impact on the planets’ observable properties. Furthermore, they can create complex organic molecules which are necessary for habitability. Thus, information on the formation, composition, optical properties, and chemistry of clouds and hazes is highly desired to develop reliable atmospheric models. Clouds in exoplanetary atmospheres may originate from the condensation of silicates or other refractory materials. Silicates seem to become the prime target for future astronomical observations of cloudy atmospheres. Models describing atmospheres of exoplanets and brown dwarfs point to the necessity of including nanometer- to micrometer-sized grains of silicates. Evidence of silicate grain absorption has also been found in the observational mid-IR spectra. However, high-temperature laboratory studies of optical and structural properties of refractory materials (including silicates) and of gas-grain chemistry needed for the decoding of astronomical spectra and for the development of reliable atmospheric models present practically uncharted territory. This collaborative experimental project is aimed at bridging the gap between observations and theory by i) providing unique sets of near- to mid-infrared (0.7 – 25 m) spectral data for silicate grains as well as by ii) better understanding the gas-grain interactions. The experiments will be performed at grain temperatures relevant to the majority of known extrasolar planets, in the range between 300 and 1200 K, and at pressures ranging from 10-6 bar up to 15 bar. In addition to the laboratory measurements, the project will have a direct relationship to observational exoplanetary data, their analysis, and scientific interpretation.

• DFG Programme: Research Grants