Volcanoes on Earth have rivers of red hot lava pouring down the sides or massive explosions of gas, rock and dust rising into the sky. But in space volcanoes are quite different.
Mars has four large volcanoes – the biggest is Olympus Mons. It is 27 kilometres high (three times the height of Mount Everest) and 500 kilometres wide (bigger than Tasmania). The volcanoes on Mars haven’t erupted for more than two million years.
The planet Venus always has ancient volcanoes on its surface. The biggest is Maat Mons – eight kilometres high. From above, some of the volcanoes look like pancakes and others have strange patterns that make them look like ticks.
Scientists think a few of the volcanoes on Venus are still active, eruptions ash onto the ground.
The most active volcanoes in the solar system are on Jupiter’s moon Io. Because it orbits close to Jupiter, it is always tugged and stretched by the planet’s gravity. This causes Io’s surface to break open and volcanoes form.
In some places they erupt with hot sulphur, which smells like rotten eggs. Near Io’s north and south pole, volcanoes blast out ‘slushies’ made from water, methane and ammonia. These ‘slushie’ volcanoes are called cryovolcanoes – cryo means cold.
Saturn’s moon Enceladus has many cryovolcanoes. A few years ago, the Cassini spacecraft flew through the plume of a cryovolcano, which contains water, nitrogen, methane and carbon dioxide. Scientists believe the water came from an undersea ocean.
The coldest cryovolcanoes in the solar system are on Neptune’s moon Triton. This faraway moon blasts jets of liquid nitrogen, which is almost -200 degrees Celsius.

Astronomers believe that there are volcanoes on other moons in our solar system, we just have to find them.