Fine-grained rim formation via kinetic dust aggregation in shock waves around evaporating icy planetesimals

TL;DR

This paper investigates the formation of fine-grained rims around chondrules through kinetic dust aggregation in shock waves caused by evaporating icy planetesimals, using one-dimensional modeling to simulate dust growth.

Contribution

It introduces a new model for FGR formation via dust aggregation in shock waves from icy planetesimals, supported by calculations matching observed rim thicknesses.

Findings

FGRs of 10-100 μm can form in shock waves around icy planetesimals.

Kinetic dust aggregation is a viable process for FGR formation.

Shock wave conditions are suitable for non-porous rim growth.

Abstract

Fine-grained rims (FGRs) are frequently found around chondrules in primitive chondrites. The remarkable feature of FGRs is their submicron-sized and non-porous nature. The typical thickness of FGRs around chondrules is 10--100 $\mu$m. Recently, a novel idea was proposed for the origin of FGRs: high-speed collisions between chondrules and fine dust grains called the kinetic dust aggregation process. Experimental studies revealed that (sub)micron-sized ceramic particles can stick to a ceramic substrate in a vacuum when the impact velocity is approximately in the range of 0.1--1 km/s. In this study, we examine the possibility of FGR formation via kinetic dust aggregation in chondrule-forming shock waves. When shock waves are created by undifferentiated icy planetesimals, fine dust grains would be released from the planetary surface due to evaporation of icy planetesimals. We consider the dynamics of chondrules behind the shock front and calculate the growth of FGRs via kinetic dust aggregation based on simple one-dimensional calculations. We found that non-porous FGRs with the thickness of 10--100 $\mu$m would be formed in shock waves around evaporating icy planetesimals.