Surface temperature and thermal phase curves of the GJ 1214 b system. Panel a: snapshot of the surface temperature distribution of a hypothetical tidally locked airless exomoon. Panel b: meridional mean effective emission temperatures of: GJ 1214 b (red line), a tidally locked airless exomoon (blue line), and an exomoon with uniform temperature (dashed line). The GJ 1214 b data are from Kempton et al. (2023). Panel c: exomoon thermal phase curves. The green, cyan, and dark blue lines represent tidally locked airless exomoons with radii of 1738 km, 5000 km, and 6000 km, respectively. The dashed line shows the thermal phase curve of an exomoon with uniform temperature and a radius of 6000 km. The exomoons orbit at 32 313 km around GJ 1214 b, and the orbital period is 0.231 Earth days.