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the largest moon of Neptune


Triton was discovered by British astronomer William Lassel, on October 10, 1846, and named for the son of Neptune, Greek god of the sea.

Facts and Figures
Diameter 1,680 mi (2,700 km) largest moon of Neptune
Mass 2.14e=22 kg
Mean Distance from Neptune 571,336 mi (354,800 km)
Rotational Period -5.9 Earth days
Surface Temperature -391 F (-235 C) coldest measured object in the Solar System
Atmospheric Pressure at Surface (Earth=1 bar) 0.000015 bars
Density (Water=1.0 grams per cubic centimeter) 2.066 grams per cubic centimeter

surface of Triton as seen by Voyager 2Triton is the only large satellite in the Solar System to circle a planet in a direction opposite to the rotation of the planet. It's relatively high density suggests that Triton has more rock in its interior than the icy satellites of Saturn and Uranus do. The combination of high density and retrograde orbit lead many scientists to suggest that Triton may have been captured by Neptune as it traveled through space several billion years ago.

The surface of Triton is marked by large circular depressions. The depressions are probably not impact craters, since they are too similar in size and too regularly spaced. Their origin may involve local melting and collapse of the icy surface. Grooves and ridges cutting across the landscape indicate fracturing and deformation of Triton's surface, which is mostly covered by nitrogen frost mixed with traces of condensed methane, carbon dioxide, and carbon monoxide. Voyager 2 images show active geyser-like eruptions spewing nitrogen gas and dark dust particles several miles into the atmosphere.

Because of its retrograde orbit, tidal interactions between Neptune and Triton remove energy from Triton, thus lowering its orbit. At some very distant time in the future it will either break up (perhaps forming a ring) or crash into Neptune.


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This page was last updated on 12/16/2014.

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