Reason for Jovian Planets
		• Because you cannot condense O by itself (but only in compounds also containing Si, Mg, Fe), you don’t have much material available for making terrestrial planets.  You are limited by the low abundance of Si, Mg, Fe:  Terrestrial planets are relatively small • Once solid H2O becomes available you have lots more material • Starting at Jupiter you can make a big enough core from solid H2O that you can gravitationally hold onto the H and He gas