The Jovian planets are miniature solar systems
• Because planets captured gas as they were forming
they had small “solar” nebulae tests of nebula theory
– Regular satellite systems
• Large moons in direct (i.e. counterclockwise), equatorial orbits
• Preserve solid material from time of formation
• Jupiter shows solar-system like density gradients
– Rings
• Moons unusual and interesting objects in their own right
– Io – most volcanically active body in solar system
– Europa – may have liquid water ocean (and life!)
– Titan – only satellite with a thick atmosphere
• Many properties are due to tidal forces and resonances