Answer: Triton

Here on boring old Earth, we’ve got plain old volcanoes that spew molten rock into the air. Elsewhere in the solar system (and presumably elsewhere in the universe), there are volcanoes of a distinctly icy nature.

These ice volcanoes, or more accurately, cryovolcanoes, are found on extremely cold planets and moons. Rather than spewing molten rock, they instead erupt and eject water, ammonia, or methane—known as cryomagma, cryolava, or ice-volcanic melt.

The first cryovolcano was observed on Neptune’s moon Triton by the 1989 flyby of the Voyager 2 space probe. Nearly two decades later in 2005, the Cassini space probe photographed cryovolcanic (geyser) eruptions on Saturn’s moon Enceladus. Since then, indirect evidence of cryovolcanic activity has been found on multiple bodies in our solar system including Europa, Titan, Ganymede, Miranda, Charon, Pluto, and Ceres. Scientists have also speculated that the Kuiper belt object Quaoar may have exhibited cryovolcanism in the past.

Detailed observations of ice volcanoes is difficult because they only appear on astronomical bodies far from Earth, requiring powerful telescopes or expensive space probes for further inquiry.