sentences:  For example, Earth's own mean temperature would be about −18 °C without any greenhouse gases, ranging from around 100 °C on the day side to −150 °C at night, much like that found on the Moon.If the atmosphere of Gliese 581d produces a sufficiently large greenhouse effect, and the planet's geophysics stabilize the CO2 levels (as Earth's does via plate tectonics), then the surface temperature might permit a liquid water cycle, conceivably allowing the planet to support life.Calculations by Barnes et al.