10/4/201Chapter 12Rings, Moons, and PlutoAstronomy 1F0311Moons of the Solar Systems2Credit: OpenStax figure 12.2•Number: 200+ and counting•Composition: rocky, icy, organic compounds•Orbits: 1/3 prograde, 2/3 retrograde2Galilean Moons•Named after discoverer Galileo (1610)•Spacecraft visits–Pioneer 10 and 11 (first visit; early 1970s flyby)–Voyager 1 and 2 (late 1970s flyby)–Galileo orbiter (1995-2008)–Juno (arrived 4 July 2016)•Increasing distance from Jupiter: Io, Europa, Ganymede and Callisto3Jupiter’s moonsCredit: NOTEXAMINABLE3Io•Left: Image from Cassini flyby (on its way to Saturn)•Below: No impact craters but lots of volcanic activity4Jupiter’s moonsCredit: Credit: (moon)4Io’s Constant ResurfacingEntire surface is very young; no craters5Jupiter’s moonsCredit: (moon)5Io’s Internal Heat Source•Io is about the same size as the Moon•Why is it not geologically dead like the Moon?•Io must have another source of heat6Credit: (moon)Jupiter’s moons6
