Terrestrial planet and asteroid belt formation by Jupiter-Saturn chaotic excitation

TL;DR

This study demonstrates that chaotic excitation caused by a near-resonant Jupiter-Saturn configuration can produce a narrow protoplanetary disk, enabling the formation of terrestrial planets and the asteroid belt with realistic properties.

Contribution

It introduces a new mechanism involving Jupiter-Saturn chaos that simultaneously explains terrestrial planet formation and asteroid belt characteristics.

Findings

Reproduced current orbits and masses of Venus, Earth, and Mars.

Depleted disk beyond 1.5 au within 5-10 Myr.

Produced asteroid belt with realistic orbital structure and composition.

Abstract

The terrestrial planets formed by accretion of asteroid-like objects within the inner solar system's protoplanetary disk. Previous works have found that forming a small-mass Mars requires the disk to contain little mass beyond ~1.5 au (i.e., the disk mass was concentrated within this boundary). The asteroid belt also holds crucial information about the origin of such a narrow disk. Several scenarios may produce a narrow disk. However, simultaneously replicating the four terrestrial planets and the inner solar system properties remains elusive. Here, we found that chaotic excitation of disk objects generated by a near-resonant configuration of Jupiter-Saturn can create a narrow disk, allowing the formation of the terrestrial planets and the asteroid belt. Our simulations showed that this mechanism could typically deplete a massive disk beyond ~1.5 au on a 5-10 Myr timescale. The resulting terrestrial systems reproduced the current orbits and masses of Venus, Earth and Mars. Adding an inner region disk component within ~0.8-0.9 au allowed several terrestrial systems to simultaneously form analogues of the four terrestrial planets. Our terrestrial systems also frequently satisfied additional constraints: Moon-forming giant impacts occurring after a median ~30-55 Myr, late impactors represented by disk objects formed within 2 au, and effective water delivery during the first 10-20 Myr of Earth's formation. Finally, our model asteroid belt explained the asteroid belt's orbital structure, small mass and taxonomy (S-, C- and D/P-types).