Meteorites are fragments of asteroids that survive the journey through space and land on Earth. Many of them contain iron–nickel metal grains, which can preserve microscopic structures formed during ancient impact events. By studying these structures, scientists can reconstruct the violent history of asteroid collisions in the early Solar System.
In this study, researchers examined metal grains from ten L-group ordinary chondrite meteorites, one of the most common types of meteorites found on Earth. The team used a technique called electron backscattered diffraction (EBSD) to analyze the crystal structures of iron–nickel metals within the meteorites. This technique allows scientists to map the internal orientation of metal crystals at very high resolution.
The researchers discovered that different types of microscopic structures appear depending on the intensity of the impact events experienced by the meteorite’s parent asteroid. For example, Neumann bands, parallel lines within iron crystals, indicate relatively weak impact shocks. These structures form when the metal lattice is suddenly deformed by stress during small collisions.
As impact energy increases, the metal can undergo additional transformations. In moderate shock events, new structures called net plessite form as the metal partially changes its crystal structure. In more intense impacts, the metal is heated enough to completely transform into a different phase and later cools to form complex patterns such as martensite and various types of plessite.
These microscopic metal structures act like geological fingerprints of past impacts. By comparing them with known shock stages in silicate minerals, scientists can better classify the shock history of meteorites and even apply this method to iron meteorites.
Understanding these impact signatures helps scientists reconstruct the collision history of asteroids and provides new insights into how planetary bodies evolved during the early formation of the Solar System.
Reference
Y. Luo et al., “EBSD analysis of iron-nickel metal in L type ordinary chondrites: 1. The microstructural shock signatures,” Journal of Geophysical Research: Planets, vol. 129, 2024, doi: 10.1029/2023JE007938
