 An atmosphere that is dense will circulate heat , potentially allowing a wide area on the surface to be habitable . For example , Venus has a solar rotation rate approximately 117 times slower than Earth 's , producing prolonged days and nights . Despite the uneven distribution of sunlight over time intervals shorter than several months , unilluminated areas of Venus are kept almost as hot as the day side by globally circulating winds . Simulations have shown that an atmosphere containing appropriate levels of CO2 and H2O need only be a tenth the pressure of Earth 's atmosphere ( 100 mbar ) to effectively distribute heat to the night side . Current technology cannot determine the atmospheric or surface composition of the planet due to the overpowering light of its parent star . 
