The Jovian planets each have a large number of moons, and each planet+moons group is like a small solar system.

• the moons range from larger than our Moon to 10 kilometers in size

• some are cold and icy – why?

• some are warm, with liquid oceans or volcanoes – why?

• what source of energy could fuel the moons' heat? (tidal forces, friction)

• where did the moons come from?
  • could some have formed when the planets formed?
  • could some be accreted planetoids?
  • could some be comets or asteroids, caught by the gravity of the major planets?

• the Cassini-Huygens spacecraft visited the moons of Saturn in summer 2004

Images of the larger moons of the solar system. [NASA, T. Parker, P. Schenk, & R. Herrick]