Triton, the largest moon of Neptune is a possible target for colonization. It has an abundance of nitrogen, methane, and water ice which can be used for fuel for rocket ships. Like Europa, it is a possibility that Triton can have a subsurface ocean with possible forms of life.
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Disadvantages
Triton is the coldest place in the solar system with temperatures so low, that the atmosphere freezes at the poles. If a base were to be built, it would require sufficient heat.
Advantages
Triton has ammonia, nitrogen, methane, and water. Rocket fuels could be made out of these resources. Triton has volcanoes that shoot out liquid water that eventually freezes. Therefore if Triton were to be colonized, it would be similar to colonizing Europe.