For 10 points, name this largest moon of the planet Neptune.
It has a radius of some 1400 kilometers, and because of its retrograde orbit, it will, within the next 100 million years or so, be torn apart to create a new ring for its host planet.  It has a tenuous nitrogen atmosphere and exhibited geysers of liquid nitrogen when Voyager 2 passed in 1989.  For 10 points, name this largest moon of the planet Neptune.
It has a radius of some 1400 kilometers, and because of its retrograde orbit, it will, within the next 100 million years or so, be torn apart to create a new ring for its host planet.  
Triton