Effects of pebble accretion on the growth and composition of planetesimals in the inner Solar System

TL;DR

This study uses N-body simulations to evaluate how pebble accretion influences the growth and composition of planetesimals in the inner Solar System, considering gas disc effects and Jupiter's formation.

Contribution

It provides new insights into the limited role of pebble accretion in terrestrial planet formation by analyzing its impact during the gas disc phase.

Findings

Pebble accretion can significantly increase solid mass in the disc.

The isotopic composition implications challenge pebble accretion's role.

Pebble accretion likely played little or no role in forming terrestrial planets.

Abstract

Recent work has shown that aside from the classical view of collisions by increasingly massive planetesimals, the accretion of mm- to m-sized 'pebbles' can also reproduce the mass-orbit distribution of the terrestrial planets. Here, we perform N-body simulations to study the effects of pebble accretion onto growing planetesimals of different diameters located in the inner Solar System. The simulations are run to occur during the lifetime of the gas disc while also simultaneously taking Jupiter's growth into account. We find that pebble accretion can increase the mass in the solid disc by at least a few times its initial mass with reasonable assumptions that pebbles fragment to smaller-sized grains at the snow line and that gas-disc-induced orbital migration effects are in force. Such a large contribution in mass by pebbles would seem to imply that the isotopic composition of the inner Solar System should be similar to the pebble source (i.e. outer Solar System). This implication appears to violate the observed nucleosynthetic isotopic dichotomy of the sampled Solar System. Thus, pebble accretion played little or no role in terrestrial planet formation.