Early Initiation of Inner Solar System Formation at Dead-Zone Inner Edge

TL;DR

This paper proposes that the inner solar system's structure originated from rocky planetesimals forming at the dead-zone inner edge of the protosolar disk early in its evolution, explaining the current orbital configuration and composition.

Contribution

It introduces a novel model where rocky planetesimals form rapidly at the dead-zone inner edge, influencing the early dynamical development of the inner solar system.

Findings

Rocky planetesimals formed around 1 au within 0.1 Myr.

Protoplanets grew without significant orbital migration.

Model explains orbital structure and rocky composition of inner solar system.

Abstract

The inner solar system possesses a unique orbital structure in which there are no planets inside the Mercury orbit and the mass is concentrated around the Venus and Earth orbits. The origins of these features still remain unclear. We propose a novel concept that the building blocks of the inner solar system formed at the dead-zone inner edge in the early phase of the protosolar disk evolution, where the disk is effectively heated by the disk accretion. First, we compute the dust evolution in a gas disk with a dead zone and obtain the spatial distribution of rocky planetesimals. The disk is allowed to evolve both by a viscous diffusion and magnetically-driven winds. We find that the rocky planetesimals are formed in concentrations around $\sim$ 1 au with a total mass comparable to the mass of the current inner solar system in the early phase of the disk evolution within $\lesssim0.1$ Myr. Based on the planetesimal distribution and the gas disk structure, we subsequently perform \textit{N}-body simulations of protoplanets to investigate the dynamical configuration of the planetary system. We find that the protoplanets can grow into planets without significant orbital migration because of the rapid clearing of the inner disk by the magnetically-driven disk winds. Our model can explain the origins of the orbital structure of the inner solar system. Several other features such as the rocky composition can also be explained by the early formation of rocky planetesimals.