Long-Term Evolution of Gas Giants and Sub-Neptunes with the JADE Code

Atmospheric escape and orbital evolution play a central role in shaping the observed exoplanet population, particularly the structure of the radius–period diagram. Features like the Neptunian desert raise fundamental questions about formation, long-term evolution and survivability. Yet, dynamical and atmospheric evolutions are usually treated separately. To address this need, we developed JADE (Joining Atmosphere and Dynamics for Exoplanets), a framework that self-consistently models the coupled evolution of secular orbital migration and atmospheric escape over billion-year timescales. JADE has successfully reproduced the misaligned orbit of the warm Neptune GJ 436 b, demonstrating how late-stage high-eccentricity migration driven by a massive outer companion can delay atmospheric loss. It is now routinely used to study the evolution of Jupiter- to Neptune-mass planets with H/He-dominated envelopes.
To study the potential erosion of gas giants into sub-Neptunes, we expanded JADE to include metal-enriched and water-dominated atmospheres. By refining atmospheric opacities and equations of state, and by implementing fractionated mass loss of hydrogen and oxygen, we enable more realistic simulations of envelope erosion and internal structure evolution. JADE is an open-source and versatile tool, and we welcome collaborations to broaden its applicability across diverse exoplanetary systems. JADE, constrained by atmospheric escape signatures from near-IR spectrographs, high-precision constraints from transit (e.g., PLATO) and radial-velocity (e.g., ESPRESSO, ANDES) surveys, as well as compositional constraints from atmospheric measurements (e.g., JWST, ARIEL), will enable population-level studies across the entire close-in planets landscape.