Titan

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Titan Largest satellite of Saturn, and the second largest in the Solar System, discovered (1655) by Christiaan Huygens. It is unique among planetary satellites in having a substantial atmosphere. It is composed of rock and water-ice in roughly equal proportions. The space probe Voyager 1 found no gaps in an opaque, reddish cloud layer c.200km (125mi) above the surface. The atmosphere consists mostly of nitrogen, with some methane and other hydrocarbon compounds. The surface temperature is 95K, at which methane can exist as solid, liquid or gas, so methane may play the role that water does on Earth, forming clouds, rain, and lakes.

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