Rilles are long, narrow depressions that can be formed by a few different processes, including:
* Lava flows: Many rilles are believed to be formed by the flow of molten lava.
* Tectonic activity: Some rilles might be formed by the movement of the Moon's crust, similar to how faults are formed on Earth.
* Impact craters: In some cases, rilles can be created by the impact of asteroids or other celestial objects.
Although they resemble valleys, rilles are distinct from valleys on Earth, which are primarily formed by erosion from water.
