Orbital positions of the K2-18 planets (colored circles) relative to the HZ are shown (Kopparapu et al. 2013). K2-18b lies near the inner edge of the conservative HZ. The dotted yellow line marks the recent Venus limit, while the region between the dash-dotted cyan line and the conservative HZ corresponds to orbital distances where water would likely remain frozen. The white regions beyond all HZ boundaries represent environments where surface liquid water is not expected to persist.