Triton, Neptune's moon

Triton is the seventh in distance and the largest moon of Neptune. It is named after the sea god, son of Poseidon in Greek mythology.
Triton was discovered Oct. 10, 1846 by British astronomer William Lassell, 17 days after the discovery of Neptune.
Its orbit is retrograde, i.e. its direction is opposite to the rotation of Neptune, Triton reveals that this feature is an external object that was captured by the giant planet.
The moons that have a retrograde orbit, can not have been formed from the same cloud of dust as their planets, in the primitive nebula.
They are objects made ​​elsewhere, probably came from the Kuiper Belt, not far away.
Triton is the seventh largest natural satellite in the solar system. Due to the mass of Triton, this capture is exceptional in the solar system known as the captured objects, have sizes much smaller. We know other captured moons like Jupiter's outer moons, Ananke, Carme, Pasiphae and Sinope and Saturn, Phoebe, also a retrograde orbit, but all have less than 10% of the diameter of Triton.

The photo against the gas giant planet Neptune and its moon cloud, Triton was captured by the camera of Voyager 2.
It managed to capture these two wonderful growing light, sets, that of Neptune and Triton in the same phase in 1989.
This picture could never be taken from Earth because Neptune, the farthest of the planets of the solar system, never shows a crescent-lit, to the Earth.
We guess here, the slight blue tint familiar Neptune. Neptune emits more light than it receives from the Sun. Passing by Triton, Voyager 2 has revealed a complex and active, which has a thin atmospheric layer and ground dotted with volcanoes strangely.
Some images of Triton taken by Voyager 2 in 1989, show a fascinating field, a thin atmosphere and even ice volcanoes.
Triton, its characteristics (size, mass, composition, temperature, density), similar to Pluto. And as that of Pluto, the icy surface of Triton is composed mainly of nitrogen, with plenty of water ice (H2O), some carbon dioxide (CO2), some methane (CH4) and carbon monoxide (CO).

Triton's surface is highly reflective, its albedo varies from 62% to 89%, by comparison, the Moon has an average albedo of 13.6%.
It appears from the observations of Voyager 2, Triton has a core, mantle and crust.
Moreover, the mass of the nucleus would be sufficient to maintain an internal heat source by radioactive decay of its isotopes (thorium 232, uranium-238 and potassium 40), as in the core of the Earth.
Voyager 2 also confirmed the existence of thin rings around Neptune, invisible from Earth.

Image: Neptune and its largest moon, Triton, the seventh largest natural moons of the solar system.
Image NASA - Voyager 2