BellaOnline Forums Education Astronomy Triton - Neptune's Captured Moon *new*

The Solar System's large moons tend towards the weird and wonderful, and Triton is no exception. It has ice volcanoes, a strange 'cantaloupe terrain", and crazy seasons. It's the only large moon to orbit in the wrong direction, so it didn't form near Neptune. But where did it come from?

Triton - Neptune's Captured Moon

Global Color Mosaic of Triton, taken by Voyager 2 in 1989

Credit: NASA / Jet Propulsion Lab / U.S. Geological Survey

Triton is one of only three objects in the Solar System known to have a nitrogen-dominated atmosphere, Earth being another of the three. It's so cold that most of Triton's nitrogen is condensed as frost, making it the only satellite in the Solar System known to have a surface made mainly of nitrogen ice. The pinkish deposits of the south polar cap are believed to contain methane ice, which has reacted under sunlight. The dark streaks overlying these pink ices are believed to be an icy and perhaps carbonaceous dust deposited from huge geyser-like plumes, some of which were found to be active during the Voyager 2 flyby. The bluish-green band visible in this image extends all the way around Triton near the equator; it may consist of relatively fresh nitrogen frost deposits. The greenish areas includes what is called the cantaloupe terrain, whose origin is unknown, and a set of "cryovolcanic" landscapes apparently produced by icy-cold liquids (now frozen) erupted from Triton's interior. [NASA]

Triton's orbit is definitely askew. The diagram shows Triton's orbit compared to most other moons. You can see that it's highly tilted and orbiting in the opposite direction.

A geological map of Triton's surface features has been created by Antonio Ciccolella from Voyager 2 data. [You can click to enlarge the map.] Only 40% of Triton's surface was imaged by the spacecraft. Of what we can see Triton is relatively flat, varying no more than a kilometer. Yet the surface is quite varied. I wonder if further exploration would find it as fascinating as Pluto.