Triton, Neptune’s largest moon, breaks the rules of the solar system. It is the only large moon that orbits backward against its planet’s rotation, and it is slightly bigger than Pluto. This episode synthesizes planetary science papers, survey data and Voyager 2 mission logs to explain how Triton was likely hijacked from the Kuiper Belt as half of a binary pair, how its capture wrecked Neptune’s original moons, and why it now makes up over 99.5 percent of the mass orbiting Neptune.

From there the conversation moves to Triton’s alien geology: water-ice bedrock, ammonia-water cryolava, the 100-kilometer Leviathan Patera, cantaloupe terrain shaped by diapirism, and nitrogen geysers driven by a solid greenhouse effect at 38 Kelvin. The hosts cover Triton’s thin nitrogen atmosphere, tholin haze, the fact that Voyager 2 mapped only about 40 percent of the surface, proposed return missions like Trident, and the moon’s eventual fate as it spirals inward toward the Roche limit and is shredded into a ring system that could rival Saturn’s.

• Why Triton’s retrograde orbit points to a violent three-body capture from the Kuiper Belt
• How tidal heating melted Triton from the inside and keeps it geologically active today
• Cryovolcanism, Leviathan Patera and the lava-lamp mechanism behind cantaloupe terrain
• The solar-powered nitrogen geysers Voyager 2 caught erupting eight kilometers high
• Subsurface ocean potential, astrobiology stakes and Triton’s future death spiral into Neptune