Triton, in Greek
mythology the son of Poseidon,
is the largest of Neptune's thirteen
confirmed natural satellites and
with a diameter of 2,700 kilometers is almost ¾ the size of Earth’s
moon. It has a tenuous almost
non-existent atmosphere composed mainly of nitrogen and methane and a
surface temperature of -240 Celsius, but because it is geologically
active (its surface is covered in ice volcanoes) there is a
possibility of aquatic life existing beneath its frozen
exterior.