Assessment of Cr isotopic heterogeneities of volatile-rich asteroids based on multiple planet formation models

TL;DR

This study uses Cr isotopic variations in carbonaceous chondrites to estimate the formation regions of volatile-rich asteroids, considering planetary formation models, disk turbulence, and supernova influences.

Contribution

It introduces a novel approach to determine asteroid formation regions using Cr isotopic heterogeneities and models the effects of planetary gaps and supernovae on these regions.

Findings

Volatile-rich asteroids likely formed around 2 parsecs from supernovae.

Isotopic heterogeneities are preserved under weak turbulence conditions.

D-type asteroids are generally located beyond most C-complex asteroids.

Abstract

Describing the comprehensive evolutionary scenario for asteroids is key to explaining the various physical processes of the solar system. Bulk-scale carbonaceous chondrites (CCs) possibly record the primordial information associated with the formation processes of their parent bodies. In this study, we tried to estimate the relative formation region of volatile-rich asteroids by utilizing the nucleosynthetic Cr isotopic variation (54Cr/52Cr) in bulk-scale CCs. Numerical calculations were conducted to track the temporal evolution of isotopically different (solar and presolar) dust and 54Cr/52Cr values for mixed materials with disk radius. First, we found that isotopic heterogeneities in CC formation regions would be preserved with a weak turbulence setting that would increase the timescales of the advection and diffusion in the disk. Second, we assessed the effects of gaps formed by giant planets. Finally, the distance from the injected supernovae and Cr isotopic compositions of the presolar grains were investigated in terms of the estimated formation region of CCs. In our results, a plausible formation region of four types of CCs can be obtained with the supernova from approximately 2 pc and typical Cr isotopic compositions of presolar grains. Among the parent bodies of CCs (i.e., volatile-rich asteroids), B-type asteroids formed in the outermost region, which is inconsistent with the present population, showing that D-type asteroids are generally located beyond most of the C-complex asteroids. Both the initial and present orbits of asteroids might be explained by the scatter attributed to the inward-outward migration of Jupiter and Saturn.