Do Rocky Exoplanets Retain Their Atmospheres?

The presence or absence of a planetary atmosphere is the outcome of a multi-billions-year long struggle between the planetary surface gravity, its outgassing rate, its magnetic field, and the stellar XUV and particle flux incident upon the world. The worlds found to transit nearby M-stars are more observationally accessible owing to the diminutive sizes and low luminosities of the central stars. However, recent work has demonstrated that these stars remain active and sustain high XUV fluxes for billions of years, much longer than the epoch of atmospheric production. With powerful infrared observatories in orbit and on the ground, we are now mapping the cosmic shoreline that separates airlines worlds from those with atmospheres, possibly even ones containing biosignature gases.