Discovered by brewer by trade and amateur astronomer by passion William Lassell just weeks after the confirmation of the new planet Neptune at the advice of his friend polymath John Herschel to search for moons, the largest and what was considered until 1949 to be the lone satellite came to be named after Triton.
The son of sea god Poseidon and Amphitrite—was half man and half fish his name was broadly used as term for merfolk generally in classical scholarship. Triton’s relatively substantial size, as big as the Earth’s moon, and uniquely retrograde orbit suggest Triton was a dwarf planet, like Pluto, captured by the gas giant. Composed primarily of water ice and frozen nitrogen with a rocky core, it is one of the few known satellites to be geologically active and has cryovolcanic activity and ice geysers that give the moon uniform but ridged terrain described as akin to the surface of a cantaloupe.