Winter's coming in Titan

False-color images from NASA's Cassini spacecraft show the development of a hood of high-altitude haze -- which appears orange in this image -- forming over the south pole of Saturn's moon Titan. These images were obtained on May 22 and June 7, 2012 by the visual and infrared mapping spectrometer in infrared wavelengths. Scientists assigned the colors red, green and blue to wavelengths mostly sensitive to the stratosphere, troposphere, and surface components, respectively. The newly discovered feature appears several hundred miles (kilometers) above the surface. When Cassini arrived at Saturn, it saw a hood of clouds and haze over Titan's north pole, which was experiencing winter. The south pole was basically clear, except for sporadic methane clouds. The seasons have been changing and the circulation in the upper atmosphere goes now from the illuminated north pole to the cooling south pole, causing downwellings over the south pole and formation of the hood.

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Interestingly, there's a season cycle like on Earth. Titan, one of Saturn's 60 moons, is the only moon in the solar system large enough to support an atmosphere; it has a lot of the same circulation features as Earth, but done with completely different substances that work at different temperatures.

On Earth, water forms liquid and is relatively active as a vapor in the atmosphere. But on Titan, water is a rock. It's not more volatile on Titan than sand is on Earth.
Methane-natural gas-assumes an Earth-like role of water on Titan. It exists in enough abundance to condense into rain and form puddles on the surface within the range of temperatures that occur on Titan.

The ironic thing on Titan is that although it's much colder than Earth, it actually acts like a super-hot Earth rather than a snowball Earth, because at Titan temperatures, methane is more volatile than water vapor is at Earth temperatures...