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Changing Seasons

November 11, 2014

The cool, crisp days of autumn are one of the benefits of the change in seasons — a pleasant break from the hotter, muggier days of summer, when Earth’s northern hemisphere was receiving more sunlight.

Other worlds go through their own cycle of seasons, with their own changes in temperature and humidity. One example is Titan, the largest moon of Saturn, where it’s the middle of spring in the northern hemisphere.

Titan’s atmosphere supports a cycle of clouds and precipitation that’s similar to the water cycle here on Earth. But Titan is hundreds of degrees colder than Earth, so its clouds are made not of water, but of liquid hydrocarbons — mainly ethane and methane.

McDonald Observatory astronomer Laurence Trafton is studying the extent to which these compounds move across Titan as the seasons change. The leading idea says that when it’s summer, the warmer temperatures evaporate some of the ethane and methane from the lakes around that hemisphere’s pole. Some of those gases then migrate to the other pole, where it’s winter. In the colder air, they condense to form clouds, which produce drizzle, filling the lakebeds on that hemisphere.

Trafton is studying observations that show how the methane is distributed across the big moon as it moves from one hemisphere to the other from season to season. His analysis will help reveal how the skies on Titan change with the seasons.

We’ll have more about Titan tomorrow.


Script by Damond Benningfield, Copyright 2014


Today’s program was made possible by a grant from the NASA Science Mission Directorate.

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