Planet formation theories in the past have been mostly constrained via the observed masses and orbital distances of exoplanets. Since the launch of the JWST it is clear that additionally also the atmospheric composition of exoplanets has to be taken into account. While we are still waiting for the major results from JWST, it is clear that the range of exoplanet atmospheres spans from sub- to super-solar values. While classical formation scenarios can explain super-solar abundances of exoplanetary atmospheres only via additional planetesimal accretion, sub-solar abundances are explained by the absence of planetesimal accretion. However, it is unclear why planetesimal accretion should be efficient only in some cases. On the other hand, in the pebble drift and evaporation scenario, inward drifting pebbles evaporate at ice lines and release their volatiles into the gas phase of the disc, enhancing the inner disc's volatile content to super-solar values owing to the faster inward drift of pebbles compared to the viscous accretion speed of the gas. Consequently forming planets forming in the inner disc can accrete volatile enriched gas and achieve super-solar abundances (Schneider & Bitsch 2021a), while planets forming in the outer disc remain sub-solar in their atmospheric abundances, because the cold outer disc does not allow the evaporation of volatiles. This model thus allows the formation of planets with super- and sub-solar abundances. We will present here outcomes and implications of this model by using the constraints of the characterized hot Jupiters WASP-77A b and tau Boötis b. In particular, we will discuss where the planetary embryos that formed the now observed planets originated from (Bitsch et al. 2022) and how the prediction of this model can be tested by future observations with JWST (Schneider & Bitsch 2021b).
[Poster PDF File]