The pHZ of Gl 581 for a super-Earth of a) M = 3.1   M_⊕ and b) M = 4.3   M_⊕ as a function of planetary age. The relative continental area is varied from 0.1 to 0.9. The stellar luminosity is assumed to be 0.013   L_⊙. Following Selsis et al. (2007) and references therein, the stellar age is at least 7 Gyr, indicated by a dashed line. For comparison, we show the positions of Venus, Earth, and Mars scaled to the luminosity of Gl 581. Note that the position of Gl 581g almost exactly coincides with the luminosity-scaled position of Earth.