The smell of a cattle yard on a summer afternoon isn't pleasant. But it's like a garden full of honeysuckle compared to the environment around a large lake near the south pole of Titan, the largest moon of Saturn.
Titan is hundreds of degrees colder than Earth is, so the lake -- named Lake Ontario -- is filled not with water, but with liquid methane, ethane, and other hydrocarbons -- the same smelly compounds emitted by cattle. During summer, as the lake warms, some of the methane evaporates and wafts into the air. In fact, the lake produces more methane gas than all the cows on Earth combined.
Lake Ontario is about the same length as its terrestrial namesake, and it has a similar footprint -- it's shaped like a footprint. The Titan version covers a larger area -- though not as much area as it used to. Since it was discovered in 2004, its shoreline has receded by about six miles.
That's because it's been summertime in Titan's southern hemisphere -- a season that lasts about eight years. The season warms the lake, increasing evaporation. As the liquid disappears, the lake shrinks and gets shallower. By summer's end, its greatest depth was around 30 feet.
Now, though, it's autumn at Lake Ontario, with winter to follow in a few years. As the southern hemisphere cools, it's likely that rains or condensation will replenish the lake -- filling it with a "smelly" brew.
We'll talk about plans to sail one of Titan's lakes tomorrow.
Script by Damond Benningfield, Copyright 2010
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