It's December the 23rd. On this day in 1672 Italian-born French astronomer Giovanni Domenico Cassini (1625-1712) discovered a new moon of Saturn. Cassini had already discovered one of Saturn's moons and would discover two more. He didn't bother to name them - except to christen the quartet
Sidera Lodoicea (the stars of Louis) to honor King Louis XIV. It was another 175 years before John Herschel suggested names for them.
Cassini the spacecraft has studied the moon Rhea that Cassini the astronomer discovered. In
this photo of Rhea centered on the south pole you can see the two very different types of terrain on the moon.