# Chondrules as fallout from vaporizing impacts in the solar nebula

**Authors:** Nick Choksi, Eugene Chiang, Harold C. Connolly Jr., Zack Gainsforth, Andrew J. Westphal  
**arXiv:** [2009.10093](https://arxiv.org/abs/2009.10093)  
**Date:** 2020-09-21  
**Summary page:** https://www.summarizepaper.com/en/paper/2009.10093v1/

## Key points

- Choksi et al. study the formation of chondrules in the early solar nebula through planetesimal collisions
- Hot silicate vapor from collisions expands into cold hydrogen environment, entraining collisional debris and proto-chondrules
- Vapor, dust, and proto-chondrules reach a common temperature as cloud expands, with cooling process influenced by condensation and radiative losses
- Particles within specific size range swept back into cavity left by condensed vapor; re-agglomerate with parent bodies based on location in solar system
- Model predicts older chondrules would have larger sizes if asteroids were initially larger and gas densities decayed monotonically
- Research addresses challenges in understanding chondrule production efficiency and origin of calcium-aluminum-rich inclusions (CAIs) within meteorites

## Summary

In their study, Choksi et al. explore the formation of chondrules - mm-sized spheres found in the oldest meteorites - as a result of planetesimal collisions in the early solar nebula. They focus on the process by which hot and dense silicate vapor released from these collisions expands into the cold and rarefied nebular hydrogen environment. The authors propose that collisional particle debris, including chondrule precursors, is entrained by the vapor cloud and melted through gas conduction and radiation emitted by dust grains that condense out of the cloud. Through a combination of conduction and radiation, the vapor, dust, and proto-chondrules are locked to a common temperature that decreases as the cloud expands. Initially, latent heat released by condensation slows down the cooling process; however, radiative losses eventually accelerate it until all remaining vapor condenses. This leaves behind a cavity devoid of pressure which is then filled with nebular gas. The authors suggest that particles within a specific size range are swept back into this cavity; those that are not too small can sediment onto the remains of planetesimals before being torn away by solar tides. As a result, particles that re-agglomerate with their parent bodies have distinct size ranges depending on their location in the solar system. By analyzing thermal histories of chondrules in asteroids and comet 81P/Wild-2, Choksi et al. were able to replicate these processes for colliding planetesimals around 100 km in radius - consistent with sizes observed in minor bodies within our Solar System. Their model also predicts that older chondrules would have larger maximum sizes and cooled more slowly if asteroids were initially larger and nebular gas densities decayed monotonically. The study also addresses challenges such as understanding the efficiency of chondrule production and the origin of calcium-aluminum-rich inclusions (CAIs) within meteorites. Overall, this research provides valuable insights into how chondrules may have formed as fallout from vaporizing impacts in the primordial solar nebula.