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This picture shows geysers near Triton's South Pole. The geysers shoot dark material high into Triton's atmosphere. This dark plume settles back down to Triton's surface. Scientists think we can tell which way the wind blows on Triton because of this! Do you see how the geyser plumes point from lower-left towards upper-right in this picture?
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Image courtesy NASA/JPL/USGS.

The Atmosphere of Triton

Triton is by far the largest moon of Neptune. It is slightly smaller than Earth's Moon. The surface of Triton is colder than the surface of any other planet or moon in our Solar System. It is so cold on Triton that almost everything freezes, even gases. That's why it is surprising that Triton has an atmosphere.

Triton's atmosphere is very, very thin. The air pressure on Earth is more than 50,000 times higher than on the surface of Triton! Most of the air on Triton is the gas nitrogen... just like on Earth! Most of the nitrogen on Triton is frozen. It is on the ground in the form of frost. Some of the nitrogen frost warmed up just a little and evaporated. That's what makes Triton's thin atmosphere.

Triton also has several ice geysers near its South Pole. The geysers shoot nitrogen, dust, and chemicals containing methane high into the atmosphere. Triton has clouds of nitrogen ice particles in the lower parts of its atmosphere. There is also a haze layer made of hydrocarbons which forms when sunlight hits methane molecules in Triton's air.

There are dark areas on the ground near several geysers. Scientists think winds blew the dark materials from the geysers in that direction. So it seems like Triton has winds!

Earth's atmosphere has layers, and so does Triton's. Triton's atmosphere has a troposphere, a thermosphere and an exosphere. It does not have a stratosphere. The top of the atmosphere is about 800 km (500 miles) above Triton's surface.

Last modified July 13, 2009 by Randy Russell.

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