Planetary Embryo Bow Shocks as a Mechanism for Chondrule Formation

TL;DR

This study investigates whether planetary embryo bow shocks could have formed chondrules by simulating shock conditions around Mars-sized bodies, considering atmospheres and radiative effects, and compares results with chondrule formation constraints.

Contribution

It introduces radiation hydrodynamics simulations of planetary embryo bow shocks, including atmospheres and radiative transfer, to assess their role in chondrule formation, a novel approach in this context.

Findings

High-mass atmospheres can produce temperatures consistent with chondrule formation.

Cooling rates are often too high, challenging the viability of bow shocks as the sole formation mechanism.

Radiative conditions significantly influence shock thermal profiles.

Abstract

We use radiation hydrodynamics with direct particle integration to explore the feasibility of chondrule formation in planetary embryo bow shocks. The calculations presented here are used to explore the consequences of a Mars-size planetary embryo traveling on a moderately excited orbit through the dusty, early environment of the solar system. The embryo's eccentric orbit produces a range of supersonic relative velocities between the embryo and the circularly orbiting gas and dust, prompting the formation of bow shocks. Temporary atmospheres around these embryos, which can be created via volatile outgassing and gas capture from the surrounding nebula, can non-trivially affect thermal profiles of solids entering the shock. We explore the thermal environment of solids that traverse the bow shock at different impact radii, the effects that planetoid atmospheres have on shock morphologies, and the stripping efficiency of planetoidal atmospheres in the presence of high relative winds. Simulations are run using adiabatic and radiative conditions, with multiple treatments for the local opacities. Shock speeds of 5, 6, and 7 km/s are explored. We find that a high-mass atmosphere and inefficient radiative conditions can produce peak temperatures and cooling rates that are consistent with the constraints set by chondrule furnace studies. For most conditions, the derived cooling rates are potentially too high to be consistent with chondrule formation.