Atmospheric retention and observational boundary for highly irradiated rocky exoplanets

Determine whether highly irradiated rocky exoplanets retain atmospheres or are stripped bare by stellar irradiation, and observationally map the boundary separating atmosphere-bearing from airless rocky worlds to anchor theoretical predictions and guide target selection for follow-up observations.

Background

Understanding whether close-in rocky exoplanets can maintain atmospheres under intense stellar irradiation is central to exoplanet science and directly impacts theories of atmospheric escape, outgassing, and surface–atmosphere interactions. Conceptual frameworks such as the “cosmic shoreline” suggest a boundary between atmosphere-bearing and airless bodies, but its location is uncertain and likely not sharp due to variations in volatile inventories, stellar XUV evolution, and escape processes.

JWST secondary eclipse measurements, particularly with MIRI, now enable direct constraints on dayside thermal emission that can help distinguish bare-rock from atmospheric scenarios. However, photometric degeneracies and systematics complicate interpretation, underscoring the need to observationally map the transition between the two regimes across the population of highly irradiated rocky planets.