Cosmic History and a Candidate Parent Asteroid for the Quasicrystal-bearing Meteorite Khatyrka

TL;DR

This study investigates the origin of the unique quasicrystal-bearing meteorite Khatyrka, suggesting its parent body is the asteroid 89 Julia, based on cosmic-ray exposure ages, shock history, and spectral analysis.

Contribution

It provides new measurements of cosmic-ray exposure and shock ages for Khatyrka, and proposes a specific asteroid parent body, linking mineral evidence to celestial origin.

Findings

Cosmic-ray exposure age of 2-4 million years.

Recent shock event (<600 million years ago) in Khatyrka.

Likely parent asteroid is 89 Julia, based on spectral and orbital data.

Abstract

The unique CV-type meteorite Khatyrka is the only natural sample in which "quasicrystals" and associated crystalline Cu,Al-alloys, including khatyrkite and cupalite, have been found. They are suspected to have formed in the early Solar System. To better understand the origin of these exotic phases, and the relationship of Khatyrka to other CV chondrites, we have measured He and Ne in six individual, ~40-{\mu}m-sized olivine grains from Khatyrka. We find a cosmic-ray exposure age of about 2-4 Ma (if the meteoroid was <3 m in diameter, more if it was larger). The U,Th-He ages of the olivine grains suggest that Khatyrka experienced a relatively recent (<600 Ma) shock event, which created pressure and temperature conditions sufficient to form both the quasicrystals and the high-pressure phases found in the meteorite. We propose that the parent body of Khatyrka is the large K-type asteroid 89 Julia, based on its peculiar, but matching reflectance spectrum, evidence for an impact/shock event within the last few 100 Ma (which formed the Julia family), and its location close to strong orbital resonances, so that the Khatyrka meteoroid could plausibly have reached Earth within its rather short cosmic-ray exposure age.