1.   In this mission, scientists hope to learn what makes up Saturn, the planet encircled by rings, and Titan, the largest moon in the system.

2.   More surprising to scientists are the hints that Callisto, the outermost of the largest Jovian moons, may also have a subsurface ocean.

3.   That demolishes a long-held idea that Pluto and Triton, the largest moon of Neptune, were virtual twins.

4.   The four largest moons of Jupiter are worlds unto themselves.

5.   Their eagerness to keep Galileo going has been fed by its most recent observations, especially those revealing the four largest Jovian moons to be spectacularly diverse worlds.