The excitation of a primordial cold asteroid belt as an outcome of the planetary instability

TL;DR

This paper proposes a new mechanism where the giant planet instability, specifically the 'Jumping Jupiter' scenario, excites the primordial asteroid belt's orbits, and subsequent Solar System evolution reduces this excitation to current levels.

Contribution

It introduces a novel excitation mechanism for the asteroid belt during the planetary instability phase, linking Jupiter's orbital jumps to belt excitation and subsequent orbital evolution.

Findings

Jupiter's high eccentricity and inclination during instability excite the asteroid belt.

The asteroid belt's excitation level is initially higher than current observations.

Solar System evolution can reduce the belt's excitation and deplete its mass significantly.

Abstract

The main asteroid belt (MB) is low in mass but dynamically excited. Here we propose a new mechanism to excite the MB during the giant planet ('Nice model') instability, which is expected to have featured repeated close encounters between Jupiter and one or more ice giants ('Jumping Jupiter' -- JJ). We show that, when Jupiter temporarily reaches a high enough level of excitation, both in eccentricity and inclination it induces strong forced vectors of eccentricity and inclination across the MB region. Because during the JJ instability Jupiter's orbit `jumps' around, the forced vectors keep changing both in magnitude and phase throughout the whole MB region. The entire cold primordial MB is thus excited as a natural outcome of the JJ instability. The level of such an excitation, however, is typically larger than the current orbital excitation observed in the MB. We show that the subsequent evolution of the Solar System is capable of reshaping the resultant over-excited MB to its present day orbital state, and that a strong mass depletion ($\sim$90$\%$) is associated to the JJ instability phase and its subsequent evolution throughout the age of the Solar System.