IO'S ON FIRE

Volcanoes in Our Solar System and Beyond

- Alice Andre-Clark

Earth isn't the only place with volcanoes. Astronomers have found evidence of volcanoes on other planets and moons in our solar system, and even on exoplanets. These are planets outside our solar system that orbit other stars. Beyond Earth, we can see the inactive volcanoes that long ago carved out the landscapes of planets and moons. We can also find some active volcanoes and a different, much chillier kind of volcano.

Where is the biggest volcano in the solar system? Which celestial body is the site of the most volcanic activity in the solar system? Could all these volcanoes be a clue to where in space we might find extraterrestrial life?

Mars: Volcanic in a Big Way

Aside from Earth, Mars is the planet we know most about, geologically speaking. The Mariner 9 mission sent a spacecraft to orbit Mars in 1971. Its photographs showed this planet was home to volcanoes; calderas, or volcanic craters; and lava plains, or fields of lava left over after an eruption. For a long time, scientists assumed that all these volcanoes were inactive. But in 2022, scientists studying orbital photos of Mars discovered an active volcanic formation. It meant there must be a rising plume of hot rock beneath the crust.

An elevated region of massive volcanoes called Tharsis covers one quarter of Mars. Volcanoes in Tharsis include Olympus Mons, the tallest volcano in the solar system. It's a shield volcano, which means it has a broad, domed shape. Olympus Mons is as wide as the state of Arizona and has a peak that towers 16 miles (25 kilometers) above the surrounding plain. That's nearly three times the height of Mount Everest!

Volcanoes on Mars are big for a couple of reasons. Because of the low gravity on Mars, volcanoes need very large magma chambers to generate enough pressure to produce an eruption. So, when a volcano on Mars erupts, the eruption can be massive.