Size Triton is the largest moon of the planet Neptune. It is the seventh largest moon in the solar system. Seven good-sized moons have been discovered in our solar system. Then there is a large difference in size, so Triton is more massive than all the smaller moons together.Triton which itself is 2700 km in diameter and the mass is about 21,400,000,000,000,000,000,000 kg. If desired places, this is probably 21,400 billion tonnes.TemperatureThere are colder in the solar system, but the coldest ever recorded on the surface of Triton. It was less than 235 degrees C (minus 391 degrees F) so it's pretty cool. There are clear indications that the interior of Triton may be hotter. One of these indications has geysers, apparently dust.AtmosphereTriton nitrogen gas and has a very thin atmosphere of nitrogen and methane probably. Clouds, possibly of frozen nitrogen, form atmosphere.SurfaceThe surface of Triton is mostly rocky, but there are indications ice areas, yes, but not as much water as one of the moons of Jupiter, appears to have some. LifeTeen considered a cool place to live may sound strange, but remember that the idea really little of life beyond our home planet, so although I would say that life on the surface of Triton is very unlikely, the idea of the life in liquid water, or water and ammonia inside Triton is something that is taken seriously.