While exploring planets I often find active volcanic fumaroles. These are openings in the planet’s surface that emit steam and volcanic gases, such as sulphur dioxide and carbon dioxide. They can occur as holes, cracks, or fissures in areas where magma has risen into the planet’s crust without erupting.
This video shows the sort of thing I have found.
Here is another video of my discoveries.
A video of the rover returning to the ship.