Abstract:

An atmosphere is what remains after you add the gains to, and subtract the losses from what was initially present on the planet - to vaguely follow a quote by David Stevenson. I will outline the key elements to theoretically understand the origins and evolution of atmospheres and to support their study by modeling solar system and planet formation.

Three component-processes closely relate to planetary atmospheres: (1) the formation and evolution of the protoplanetary nebula, that provides the material and early environment, (2) the planetesimal properties and accretion history that have consequences for atmospheric survival, enrichment and out-gassing once the planetary embryos or cores are formed, (3) the interaction of the atmosphere with and its response to the stellar environment once the nebula is gone, leaving the planet completely decompressed. Direct, often non-thermal energy input from the host star is important. The resulting conditions of atmospheric loss turn the mature planet into a source of interplanetary plasma that constitutes its final controlling environment. In particular this last component has been stretched to an unimagined extreme by exoplanet discoveries.

CoRoT and Kepler have led into a regime of surprising atmospheric diversity that triggered a new level of planetary population synthesis models that now address the delivery of volatiles in detailed planet formation models. That allows the study of the expected diversity in the volatile inventories of general atmospheres and outlines an architecture for a bridge between the terrestrial planet's atmospheres and those of their large exoplanet cousins.If anything is certain, then it is the diversity of exo-atmospheres.

Thus for complementarity, I will finally show an approach that might be used to explore the limits of atmospheric diversity.

Using a "theoretically tamed" extrapolation from the results of CoRoT, that I will show, and Kepler, we may estimate the limits of the diversity of bulk atmospheric properties for the planet populations to be expected for CHEOPS, TESS and PLATO.