Two-faced Japetus

Caption NASA originale:"The dark material that coats one hemisphere of Saturn's moon Iapetus is very dark, as these two processed views of the same frame can demonstrate.
The image on the left has been cleaned of cosmic rays and magnified; in this otherwise un-enhanced view, only a small part of the moon's surface, at the bottom, is visible because it is part of the bright side of Iapetus. (Only the right hand side of Iapetus is illuminated by sunlight.) The same image, shown on the right, has been contrast-enhanced to make visible the part of the illuminated side of Iapetus that is coated with dark material".