Chaotic capture of Jupiter's Trojan asteroids in the early Solar System.

TLDR: It is shown that the Trojans could have formed in more distant regions and been subsequently captured into co-orbital motion with Jupiter during the time when the giant planets migrated by removing neighbouring planetesimals.

Abstract: A collection of three papers in this issue, tackling seemingly unrelated planetary phenomena, marks a notable unification of Solar System dynamics. The three problems covered are the hard-to-explain orbits of giant planets, the evolution of the orbits of Jupiter's Trojan asteroids, and the cause of the ‘Late Heavy Bombardment’ that peppered the Moon with meteors, comets and asteroids some 700 million years after the planets were formed. Key to all these events, on this new model, was a rapid migration of the giant planets (Saturn, Jupiter, Neptune and Uranus) after a long period of stability within the Solar System. Jupiter's Trojans are asteroids that follow essentially the same orbit as Jupiter, but lead or trail the planet by an angular distance of ∼60 degrees (co-orbital motion). They are hypothesized to be planetesimals that formed near Jupiter and were captured onto their current orbits while Jupiter was growing1,2, possibly with the help of gas drag3,4,5,6 and/or collisions7. This idea, however, cannot explain some basic properties of the Trojan population, in particular its broad orbital inclination distribution, which ranges up to ∼40 degrees (ref. 8). Here we show that the Trojans could have formed in more distant regions and been subsequently captured into co-orbital motion with Jupiter during the time when the giant planets migrated by removing neighbouring planetesimals9,10,11,12. The capture was possible during a short period of time, just after Jupiter and Saturn crossed their mutual 1:2 resonance, when the dynamics of the Trojan region were completely chaotic. Our simulations of this process satisfactorily reproduce the orbital distribution of the Trojans and their total mass.