Neptune’s Moon, Triton

Triton

History

Triton was discovered in October of 1846 by British Astronomer William Lassell, after having its planet, Neptune, discovered 17 days earlier.  Triton got it’s name from the Greek God Triton, who is the son of Poseidon (in Rome, Neptune)  Lassell did not name Triton, but the name was proposed in the book Astronomie Populaire.  The name Triton was not adopted until many years later.

Composition

Orbit and Rotation

Triton has an unusual orbit for the size of the moon.  Triton orbits around its planet, Neptune, in retrograde form (opposite the normal counterclockwise direction).  Other moons of the outer solar system orbit around their planet in retrograde, but they are much smaller in size compared to Triton.  Triton revolves around Neptune in almost a perfect circle.  The one aspect of that is Triton is closer to Neptune than the Earth is to the Moon.  It’s predicted that Triton could collide with Neptune’s atmosphere in about three and a half billion years.

Like our moon, Triton rotates Neptune in synchronous rotation (one side of the moon faces the planet at all times).  Since Triton is tilted at a 40°, it’s two poles directly face the Sun during a Neptunian year.  During these times, it’s been observed that the poles go through seasonal change.

Surface Geology

There is not much known about the surface of Triton, due to the lone encounter that the Voyager 2 had when passing the planet.  However, with the images taken, we have been able to see the surface of Triton.  Through the pictures, it is seen that Triton has a very flat surface that has few minor craters. 

Also it is seen that Triton contains a very distinct terrain feature that is only found on the moon.  Called cantaloupe terrain, a series of ridges and depressions line Triton’s western hemisphere.  These fissures can be up to 30-40 km in depth, and generally each ridge is similar.  There is no known explanation for the development of these depressions, however it is known that in the depressions is dirty water ice.

Triton is also one of the few objects in the solar system with active volcanoes.  These volcanoes are not active all year though, they become re-activated when the Sun warms the surface each year.  These volcanoes contain lavas of ammonia and water.  The moon also has geyser eruptions that help show that the moon surface is active.  It is possible that these geyser eruptions could last up to a year.  Usually these eruptions consist of nitrogen gas which when blown into the atmosphere, eventually falls back down as a nitrogen frost.  These geysers are fueled by almost constant sublimation.