An Ocean Inside Triton?

Researchers are looking at the possibility that a water ocean may exist under the ice shell of Neptune's largest moon, Triton.

They theorize Triton is a Kuiper Belt object that was captured by Neptune's gravity.  They think that because Triton orbits Neptune in the opposite direction from other moons in the Solar System.  If captured, the original orbit likely would've been highly elliptical, but the current orbit is almost perfectly round.  The energy involved in slowly reshaping that orbit, along with other possible energy-producing processes, could have produced enough heat to keep a water ocean-- especially one liberally laced with ammonia-- liquid under the shell.

Of course, an energy source plus liquid water opens the possibility of life.