Saturn has a two-tone moon.
Saturn’s moon Iapetus is a study in contrasts, with a very dark hemisphere and a very light hemisphere. It’s unlike anything else in the solar system and has sparked speculation as to what is really going on.
Some scientists believe that particles from Phoebe (another, darker moon) may be falling on its surface. Others speculate that it’s due to volcanic eruptions of hydrocarbons, which would create dark patches.