How did the terrestrial planets form?
The jovian planetesimals soon became the icy, dense cores we see today surrounded by huge clouds of accreted gas. Much like the collapse of the solar nebula, these balls of gas can grow large enough to induce gravitational collapse. Remember from the star formation section that gravitational collapse involves heating up, flattening out and rotating faster. It is possible that as the jovian protoplanets collapsed, smaller particles in the surrounding disk formed into some of the moons that now orbit the individual outer planets. This makes sense, since the outer planets all have many moons and rings that orbit in the same plane, just like the planets in our solar system orbit the Sun in the same plane.
