Nice Model - Solar System Features - Trojans and The Asteroid Belt

Trojans and The Asteroid Belt

During the period of orbital disruption following Jupiter and Saturn reaching the 2:1 resonance, the combined gravitational influence of the migrating giant planets would have quickly destabilized any existing Trojan groups in the L₄ and L₅ Lagrange points of Jupiter and Neptune. During this time, the Trojan co-orbital region is termed "dynamically open". Under the Nice model, the planetesimals leaving the disrupted disk cross this region in large numbers, temporarily inhabiting it. After the period of orbital instability ends, the Trojan region is "dynamically closed", capturing planetesimals present at the time. The present Trojan populations are then these acquired scattered planetesimals of the primordial asteroid belt. This simulated population matches the libration angle, eccentricity and the large inclinations of the orbits of the Jupiter Trojans. Their inclinations had not previously been understood.

This mechanism of the Nice model similarly generates the Neptune trojans.

A large number of planetesimals would have also been captured in the outer asteroid belt, at distances greater than 2.6 AU, and in the region of the Hilda family. These captured objects would then have undergone collisional erosion, grinding the population away into smaller fragments that can then be acted on by the solar wind and YORP effect; removing more than 90% of them according to Bottke et al. The size frequency distribution of this simulated population following this erosion are in excellent agreement with observations. This suggests that the Jupiter Trojans, Hildas and some of the outer asteroid belt, all spectral D-type asteroids, are the remnant planetesimals from this capture and erosion process, possibly also including the dwarf planet Ceres.