Sinuous rilles are long, winding channels found on the surface of the Moon, particularly in the lunar maria. These features are believed to have formed from ancient lava flows that created meandering paths as they cooled and solidified. Their unique shapes resemble river valleys on Earth, but they are much larger and lack water. Scientists study sinuous rilles to understand the Moon's volcanic history and geological processes. By analyzing their structure and formation, researchers can gain insights into the Moon's past activity and the conditions that existed during its development.