Probably heat and pressure.
Triton has Nitrogen Geysers.
Some of Triton’s heat is probably tidal, but I bet most is leftover heat from Titan being capture. Titan might have been part of a huge collision when it was captured around Neptune. Its retrograde orbit might also play a part in tidal heating.
Maybe one day the human race will realize it is better to use our resources to explore and settle space, then to fight over Earth.
