Ultraviolet Venus . ... Credit Copyright: Pioneer Venus Orbiter Team , NASA Explanation: The forecast for Venus is cloudy, cloudy, cloudy. Although similar to the Earth in size and mass, Venus ' slightly closer orbit to the Sun create for it a much thicker atmosphere and a much hotter surface. ... Venus 's extremely uncomfortable climate was likely caused by a runaway greenhouse effect . Could Earth ever undergo runaway greenhouse heating like Venus? ... NASA Official: Jay Norris. ...