Chapter 8 – Moons, Rings, and PlutoidsGalilean Moons of JupiterAll four Jovian planets have extensive moon systems, and more are continually beingdiscovered. We split them into three groups based on the diameter:-Large: 2500 km-Medium: 400km - 1600km-Small: less than 300kmThe formation of Jupiter and its moon is a reference of how the Sun brought togetherthe Solar SystemIo, Europa, Ganymede, Callisto are the big moons of Jupiter.Io and Callisto are simplistic interiors and Ganymede and Europa are more complex interiorsand may have water.-Iois the innermost of Jupiter’s moons and the most geologically active object in thesolar system.-It has many active volcanoes, and its surface can be changed in a few weeks-Iohas no craters; they fill in too fast – youngest surface of any solar system object.-Not tidally locked with Jupiter-The tidal forces are huge, and provide the energy for the volcanoes-Europahas few craters; surface is water ice, possibly with liquid water below-Tidal forces stress and crack ice; water flows, keeping the surface relatively flat.-Europa has a weak magnetic field that is constantly changing strength and direction-We would expect this if Jupiter’s magnetism acted on electrically conducting fluidbelow the surface.-Ganymedeis the largest moon in our solar system – larger than Mercury-It has a history similar to Earth’s moon, but with water ice instead of lunar rock-
