Characterization of achondritic meteoroid impactors: spectra, dynamics and ablation properties

Observing meteors through a combination of spectral and multi-station trajectory measurements presents unique opportunities for mapping the compositional diversity of small Solar System bodies from various orbital sources. This research is conducted by the AMOS (All-sky Meteor Orbit System) network, providing global coverage of meteors and their emission spectra from 17 stations in Slovakia, the Canary Islands, Chile, Hawaii, Australia, and South Africa. Recent advancements from our plasma wind tunnel ablation experiments helped characterize the diagnostic spectral features of various meteorite types, enabling more efficient identification of atypical meteoroid populations not commonly recognized by meteor surveys.

We first review the emission spectral properties of individual achondrite types obtained during meteorite ablation experiments, which serve as guides for meteor spectra interpretation (Matlovič et al., 2024). Then, we present the results of our search for achondritic meteoroid impactors captured by the AMOS stations over Hawaii and the Nullarbor Plain in collaboration with the Desert Fireball Network (Devillepoix et al., 2022).

Two achondrites – likely an aubrite and an eucrite – were identified, exhibiting distinct spectral and ablation properties. We discuss their emission spectra, dynamical properties including orbital integrations studying their source and evolution, and physical properties derived from light curve, deceleration, and fragmentation modeling.

For the aubrite, spectral analysis revealed strong emissions of Mg, Si, Mn, Ca, Ti, and Li, along with a notably low Fe content, consistent with an enstatite-enriched composition. The second achondrite displayed notably higher Fe content and even stronger intensities of refractory elements (Ca, Al and Ti), consistent with compositions similar to howardites or eucrites not significantly depleted in magnesium.

Dynamical analysis placed the eucrite on an asteroidal orbit with increased eccentricity (a = 2.09 au, e = 0.78, i = 3.7°), while the aubrite originated from a short-period orbit (a = 1.16 au, e = 0.31, i = 2.3°). Orbital integrations indicate relatively stable orbits for both bodies over the past 500 years. Fitting light curves and deceleration profiles proved challenging using standard ablation and fragmentation models. Preliminary results from an individual approach accounting for differential ablation are consistent with the assumed compact differentiated meteoroid material, indicating bulk densities > 3000 kg/m³.

Characterizing atypical meteoroid populations improves our understanding of the material distribution, diversity, and evolution of small Solar System bodies. The presented results support the future identification of achondritic meteoroids by meteor surveys through spectral and physical properties. Accurate prediction of meteoroid composition also proves crucial for modeling and locating meteorite impacts, as demonstrated by the Ribbeck aubrite fall in 2024 (Spurný et al., 2024).

 

References

Devillepoix H., Tóth J., Matlovič P., Cupák M., Towner M., Sansom E., Kornoš L., Paulech T., Zigo P. (2022). A Meteor Spectroscopic Survey in the Nullarbor, Research Notes of the AAS, 6 (7), 144

Matlovič P., Pisarčíková A., Pazderová V., Loehle S., Tóth J., Ferrière L., Čermák P., Leiser D., Vaubaillon J., Ravichandran R. (2024). Spectral properties of ablating meteorite samples for improved meteoroid composition diagnostics, Astronomy & Astrophysics, 689, A323, 19 pp.

Spurný P., Borovička J., Shrbený, L., Hankey M., Neubert R. (2024). Atmospheric entry and fragmentation of the small asteroid 2024 BX1: Bolide trajectory, orbit, dynamics, light curve, and spectrum, Astronomy & Astrophysics, 686, A67, 8 pp.