2D condensation model for the inner Solar Nebula: an enstatite-rich environment

TL;DR

This study models the two-dimensional distribution of dust in the inner Solar Nebula, revealing enstatite-rich zones that align with meteorite and infrared observations, advancing understanding of planet formation chemistry.

Contribution

First 2D thermodynamic model of dust condensation in the Solar Nebula, capturing vertical and radial distribution and dynamics of enstatite-rich dust zones.

Findings

Identified enstatite-rich zones within 1 AU of the Sun.

Supported link between Mercury, enstatite chondrites, and nebula chemistry.

Aligned model results with infrared observations of protoplanetary discs.

Abstract

Infrared observations provide the dust composition in the protoplanetary discs surface layers, but can not probe the dust chemistry in the midplane, where planet formation occurs. Meteorites show that dynamics was important in determining the dust distribution in the Solar Nebula and needs to be considered if we are to understand the global chemistry in discs. 1D radial condensation sequences can only simulate one disc layer at a time and cannot describe the global chemistry or the complexity of meteorites. To address these limitations, we compute for the first time the two dimensional distribution of condensates in the inner Solar Nebula using a thermodynamic equilibrium model, and derive timescales for vertical settling and radial migration of dust. We find two enstatite-rich zones within 1 AU from the young Sun: a band ~0.1 AU thick in the upper optically-thin layer of the disc interior to 0.8 AU, and in the optically-thick disc midplane out to ~0.4 AU. The two enstatite-rich zones support recent evidence that Mercury and enstatite chondrites shared a bulk material with similar composition. Our results are also consistent with infrared observation of protoplanetary disc which show emission of enstatite-rich dust in the inner surface of discs. The resulting chemistry and dynamics suggests that the formation of the bulk material of enstatite chondrites occurred in the inner surface layer of the disc, within 0.4~AU. We also propose a simple alternative scenario in which gas fractionation and vertical settling of the condensates lead to an enstatite-chondritic bulk material.