Geysers near Triton's South Pole spew dark material high into the moon's atmosphere. As this plume settles back down to Triton's surface, it appears to indicate prevailing winds moving from lower-left towards upper-right in this image. Click on image for full size (122 Kb) Image courtesy of NASA/JPL/USGS.

Triton, by far the largest moon of Neptune, is slightly smaller than Earth's Moon. Triton has the coldest surface temperatures in our Solar System. Surprisingly, this frigid moon has an atmosphere, albeit a very thin one. Atmospheric pressure on Earth is at least 50,000 times higher than on the surface of Triton!

Another surprise... nitrogen is the main gas in Triton's atmosphere, just as it is on Earth! Triton is so cold that most of its nitrogen is on the moon's surface as frost. Some of that frost has evaporated, however, creating Triton's atmosphere. Triton also has numerous ice geysers that spew nitrogen, dust, and/or methane compounds up to 8 km (5 miles) high into the atmosphere. Scientists have detected clouds of nitrogen ice particles between 1 and 3 km (3 to 10 thousand feet) above the surface as well as a haze layer made of hydrocarbons which forms when sunlight strikes methane molecules in Triton's air. Streaks of dark deposits appear to form downwind of geysers, apparently showing the direction of seasonal prevailing winds near Triton's South Pole.

Like Earth's atmosphere, Triton's atmosphere has layers. Turbulence near the moon's surface creates a troposphere ("weather region") that rises to an altitude of 8 km (5 miles). Triton's atmosphere lacks a stratosphere, but it does have a thermosphere and an exosphere. The upper atmosphere extends to 800 or more km (500+ miles) above Triton's surface.

Triton's atmosphere seems to be warming slightly. Although it is still extremely cold, it appears that the temperature rose 5% in about a decade. Some scientists think Triton is approaching an unusually warm summer that only happens once every few hundred years.

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? Click on image for full size (122 Kb) Image courtesy of NASA/JPL/USGS.

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.

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? Click on image for full size (122 Kb) Image courtesy of NASA/JPL/USGS.

Triton is the largest moon of Neptune. It isn't quite as big as Earth's Moon. The surface of Triton is very, very cold. It 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 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 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. The top of the atmosphere is about 800 km (500 miles) above Triton's surface.