Existence of a cosmic shoreline separating atmosphere-bearing and airless terrestrial planets

Determine whether a cosmic shoreline exists that separates terrestrial planets that retain atmospheres from those that do not.

Background

The paper frames the cosmic shoreline as a putative boundary distinguishing bodies with atmospheres from those without, a concept originally motivated by trends in the Solar System and extended to exoplanets. Establishing whether such a boundary truly exists is described as a major unresolved issue in exoplanet science.

The authors seek to constrain an M-dwarf version of this boundary by combining Milky Way exoplanet data with an extragalactic sample, but they open by explicitly noting that the basic question of whether a universal dividing relation exists remains an open question.