Active volcanoes in the Solar SystemThe Earth is not the only place with volcanic activity in our Solar System. Although there are significant differences in the type and style of volcanic activity from that on Earth, several other planets and moons have or had in the geologic past volcanic activity as well:
Currently, there there are 4 known bodies of our Solar System with still active volcanic activity:
1) Our Earth
2) Io, a moon of Jupiter
3) Triton, a moon of Neptune
4) Enceladus, a moon of Saturn
Mars, Venus and the Jupiter moon Europa might still have volcanic activity as well, but there have been no direct observations of eruptions as evidence so far.
Most volcanism outside Earth seems to have occurred in the early ages of the Solar System, when the planets were still hotter: our moon had volcanic activity in the remote geologic past, between 3-4 billion years ago, when it still was hot enough to allow basaltic lava flows to erupt through the broken crust of impact craters, the maars.
Mount Olympus on Mars is the largest known volcano in the entire Solar System, Venus is dotted with thousands of volcanic features, and Io is the volcanically most active place in the System.
Most of the knowledge of volcanic activity outside Earth comes from recent space research using modern telescopes and space craft.