"There's something strange going on below the surface of Saturn's )|Death Star-looking moon Mimas. Mimas' rotation and its orbit around Saturn make the moon look like it's rocking and back forth and oscillating similar to the way a pendulum swings. The rocking motion is called Llibration, and it's commonly observed in moons that are influenced by the gravity from neighboring planets. However, using images of the moon captured by the Cassini spacecraft, Radwan Tajeddine, a research associate at Cornell University, discovered that the satellite's libration was much more exaggerated in one spot than predicted."