A comprehensive knowledge of planetary composition is essential to understand planet formation and evolution. Since planetary interiors are largely inaccessible, their compositions must often be inferred from atmospheric observations. In this context, deciphering the complex mechanisms linking a planet’s interior to its atmosphere is a key scientific challenge.

This winter school will explore these interior–atmosphere interactions across a wide range of planetary environments. We will address both physical and chemical aspects of planetary evolution — from the contraction of gas giants to the effects of volcanism and outgassing on the atmospheres of rocky planets.

In recent years, remarkable progress has been made in this field, driven by several landmark missions. NASA’s Juno mission (2016–) has transformed our understanding of Jupiter’s structure and composition, as did Cassini (2004–2017) for Saturn. On Mars, missions such as InSight (2018–2022), Mars 2020 (Perseverance) and the ExoMars Trace Gas Orbiter (2018–) have significantly advanced our knowledge of the Martian climate, interior, and geology. For Venus, ESA’s Venus Express (2006-2014) and Japan’s Akatsuki mission (2010–2024) delivered valuable insights into the planet’s atmosphere (dynamics and composition), as well as some insights on the surface activity.

Simultaneously, the discovery of thousands of exoplanets — particularly those transiting their host stars — has opened a new window into planetary interiors. By combining mass and radius measurements, we can infer their bulk composition. In some cases, direct observations of exoplanet atmospheres are now possible, revealing their chemical makeup and atmospheric dynamics, thanks to the unprecedented capabilities of JWST and high-resolution ground-based spectroscopy.

As we seek answers to the major questions surrounding the formation and evolution of the Solar System, now is a pivotal time to take stock of our current understanding and prepare for the upcoming data-rich decade. Future missions such as Mars Sample Return (2027+) and the Venus missions EnVision, DAVINCI and VERITAS (2030+) promise to deliver critical new insights. Meanwhile, the upcoming exoplanet missions PLATO (2026+) and Ariel (2029+), and the European Extremely Large Telescope (2029+) will provide essential data on atmospheric properties and internal compositions of distant worlds.

Throughout this winter school, we will offer a critical overview of the current state of knowledge on planetary interiors and atmospheres. By connecting Solar System planets to exoplanets, going from rocky planets to gas giants, and integrating theoretical modeling, laboratory experiments and observational techniques, we aim to equip participants with a broad and interdisciplinary understanding of planetary interior-atmosphere interactions.