Formation of rims around chondrules via porous aggregate accretion

TL;DR

This paper models the formation of rims around chondrules by considering porous dust aggregate accretion and growth, providing estimates consistent with observed fine-grained rims but suggesting remelting influences thicker igneous rims.

Contribution

It introduces a model that accounts for dust aggregate growth during rim formation, improving understanding of rim thickness variations in chondrites.

Findings

Estimated rim thickness matches observed fine-grained rims.

Igneous rims are thicker than model predictions, implying remelting effects.

Porous aggregate growth influences rim formation processes.

Abstract

Chondrules are often surrounded by fine-grained rims or igneous rims. The properties of these rims reflect their formation histories. While the formation of fine-grained rims is modeled by the accretion of dust grains onto chondrules, the accretion should be followed by the growth of dust grains due to the shorter growth timescale than the accretion. In this paper, we investigate the formation of rims, taking into account the growth of porous dust aggregates. We estimate the rim thickness as a function of the chondrule fraction at a time when dust aggregate accretion onto chondrules is switched to collisions between these chondrules. Our estimations are consistent with the measured thicknesses of fine-grained rims in ordinary chondrites. However, those of igneous rims are thicker than our estimations. The thickness of igneous rims would be enlarged in remelting events.