Titan (moon) - Climate

Climate

Titan's surface temperature is about 94 K (−179 °C, or −290 °F). At this temperature water ice has an extremely low vapor pressure, so the atmosphere is nearly free of water vapor. The haze in Titan's atmosphere contributes to the moon's anti-greenhouse effect by reflecting sunlight back into space, making its surface significantly colder than its upper atmosphere. The moon receives just about 1% of the amount of sunlight Earth gets. Titan's clouds, probably composed of methane, ethane or other simple organics, are scattered and variable, punctuating the overall haze. This atmospheric methane conversely creates a greenhouse effect on Titan's surface, without which Titan would be far colder. The findings of the Huygens probe indicate that Titan's atmosphere periodically rains liquid methane and other organic compounds onto the moon's surface.

Clouds typically cover 1% of Titan's disk, though outburst events have been observed in which the cloud cover rapidly expands to as much as 8%. One hypothesis asserts that the southern clouds are formed when heightened levels of sunlight during the Titanian summer generate uplift in the atmosphere, resulting in convection. This explanation is complicated by the fact that cloud formation has been observed not only post–summer solstice but also at mid-spring. Increased methane humidity at the south pole possibly contributes to the rapid increases in cloud size. There had been summer in Titan's southern hemisphere until 2010, when Saturn's orbit, which governs the moon's motion, tilted the northern hemisphere towards the Sun. When the seasons switch, it is expected that ethane will begin to condense over the south pole.