Achondrites in meteor data: Spectra, dynamics, and physical properties of candidate aubrite and eucrite impactors

TL;DR

This study analyzes high-resolution meteor spectra to identify and characterize rare achondritic meteoroids, revealing their compositions, origins, and internal heterogeneity, thus enhancing understanding of small Solar System bodies.

Contribution

First detailed identification and analysis of achondritic meteoroids from meteor spectra, linking spectral features to composition and origin.

Findings

Identified two achondritic meteoroids with aubrite-like and eucrite-like compositions.

Detected internal heterogeneity through transient spectral features indicating localized inclusions.

Linked meteoroid origins to inner-main-belt and near-Earth asteroid sources.

Abstract

Meteor spectroscopy presents new opportunities for investigating the diversity of small Solar System bodies and capturing the real distribution of present material types. We analyze 180 higher-resolution meteor spectra from the All-sky Meteor Orbit System (AMOS) network to identify meteoroids with atypical compositions. In addition to several iron bodies, we identify the first two achondritic meteoroids in our database, both likely meteorite-dropping impactors, and compare them with a reference ordinary chondrite meteoroid observed under similar conditions. Their spectra show strong compositional departures: one case has strong Mg and Si with low Fe, while the other has strong Ca, Al and Ti with low Mg. Derived relative elemental abundances imply an aubrite-like and a eucrite-like composition. The aubrite-like meteoroid exhibits unexpected enhancements in Ca, Mn and Ti in short-lived intensity spikes, which we interpret as rapid release of localized inclusions rather than bulk enrichment. This indicates that transient spectral features can reveal internal heterogeneity in achondritic meteoroids beyond their average composition. Dynamical and physical properties are consistent with these classifications: the eucrite-like meteoroid originated from an inner-main-belt orbit influenced by the $\nu_6$ resonance and shows compact ablation with low erosion and an estimated bulk density of 3.16 $\pm$ 0.10 g cm -3; the aubrite-like meteoroid came from a short-period, low-eccentricity orbit similar to some E-type near-Earth asteroids. Both events show atypical light curves, but our results indicate that robust identification of achondritic meteoroids in surveys generally requires emission spectra. This work presents one of the first detailed studies of achondrites from meteor observations and provides reference properties of atypical meteors for future surveys.