Extraterrestrial volcanoes 

Everyone remembers making their first bicarb-and-vinegar volcano back in school, because there’s a special kind of happiness that comes from watching froth pour down the sides of your badly-painted volcano and slosh onto your classroom floor. For most people, volcanoes - simulated and real - are an endless source of fascination and sometimes fear…but did you know that Earth isn’t the only place in the solar system with active volcanoes? 

Lighting up Jupiter with Io 

Io, one of Jupiter’s largest moons, is the most volcanically active world in the solar system. It’s caught in a never-ending game of tug of war between Jupiter and two of its neighbouring moons, Europa and Ganymede, which literally stretch and compress Io with with their huge and uneven gravitational forces. The actual solid rock that Io is made of can bulge out by more than 100 metres and then back again, as if Jupiter is using Io as a stress ball. 

All this friction generates a whole lot of energy inside of Io, which creates heat that drives volcanoes on the surface. Voyager 1 and 2 first spotted these volcanoes back when they sped past in 1979, noticing that not only do the volcanoes spew out molten rock like Earth’s volcanoes, but some eruptions also blast out sulfur and sulfur dioxide up to 500km above the surface. 

What’s super interesting is that some of these particles become caught up in Jupiter’s magnetic fields and flow down to the poles, where they interact with the gases there and create brilliant aurorae.

Frozen explosions of Triton 

When Voyager 2 flew past Neptune’s largest moon, Triton, it captured images of geysers erupting from the surface. Plumes of nitrogen gas and fine particles of dust were blasted up to 8 km into the air, before falling back down to the surface like a weird, nitrogen snow - the dark streaks on the image below. 

But Triton’s volcanism isn’t due to immense tidal forces like Io: instead, it’s thought to be caused by solar heating. Triton’s surface is composed of a frozen, transparent layer of nitrogen atop a darker substrate below, and when solar radiation hits the surface, it becomes trapped by the darker layer. It’s kind of like the greenhouse effect, but in a solid object. This heats up subsurface nitrogen and causes it to vaporise, and eventually there’s so much pressure that it erupts out through the crust above. 

Fountains on Enceladus 

In 2005, the Cassini spacecraft flew right through a plume that had erupted from a cryovolcano on Enceladus, a moon of Saturn. Over 100 cryovolcanoes were discovered at Enceladus’s south pole, which blast out jets of ice-water and simple organic molecules. 

Like Io, the volcanic activity on Enceladus is probably caused by the powerful gravity of Saturn and its other moons. Enceladus gets stretched and compressed, heating up the interior and creating a subsurface ocean of liquid water. Sometimes, slushy ice and other materials get shot up through an opening in the surface and out into space. Some of this material falls back to the surface, and the rest is captured by Saturn’s massive E ring and orbits around the planet, so essentially the ring fed by volcanoes. 

Our Explosive Solar System 

Other bodies in the solar system are suspected to have active cryovolcanic activity too, like Ceres, Pluto and its moon Charon, and Saturn’s moon Titan - stay tuned for more explosive updates!