A Nice Story: I am going to try to convince you that: And
everyone lived happy ever after. - The 4 giant planets formed
within 15AU or 20AU of the Sun. - Beyond them was a massive disk
that extended to ~30AU. - The 4 giant planets slowly spread due
to leakage from this disk. - Jupiter and Saturn crossed the 1:2
mean motion resonance at 700Myr - Uranus and Neptune went
unstable and scattered into the disk. - Producing the Trojans,
Kuiper belt, irregular satellites, Primitive main belt
asteroids, and lunar Late Heavy Bombardment (LHB). - Uranus and
Neptune evolve onto current orbits due to interactions with the
disk.