Spectroscopic analysis of hydrogen and silicon in bright fireballs: New insights into meteoroid composition

TL;DR

This study uses spectroscopic analysis of fireballs to explore meteoroid composition, revealing that hydrogen abundance correlates with mass and is preserved in larger cometary meteoroids, informing models of water delivery to Earth.

Contribution

It provides new insights into volatile element preservation in meteoroids and links spectral data to meteoroid size and composition, advancing understanding of Solar System materials.

Findings

Hydrogen abundance is largely independent of meteor velocity.

Larger meteoroids show higher hydrogen preservation.

Hydrogen levels in large cometary meteoroids are comparable to or exceed those in Halley's dust.

Abstract

We present a study of the high-temperature spectral component in meteor fireballs, with a particular focus on neutral hydrogen at 656.28 nm and ionised silicon doublet at 634.71 nm and 637.14 nm. By analysing spectra from the European Fireball Network (EN) that exhibit H$\alpha$ and Si~II emissions, we investigated the relationship between H and Si abundances across different meteoroid types. The plasma temperature of the high-temperature component remains independent of meteor velocity. This allows us to directly compare relative intensities of volatile hydrogen with less volatile silicon in bodies with different velocities. Our results confirmed that the H/Si value remains largely independent of meteor velocity. We show a positive correlation with photometric mass for cometary meteoroids, suggesting that larger bodies better preserve their volatile content, namely hydrogen. This correlation persists across the meteor showers, showing a physical process related to volatile preservation rather than specific parent body composition. Our data suggest that the abundance of hydrogen in large cometary meteoroids is not only higher than in CI chondrites, but is also comparable to or higher than the measured abundances in small particles of dust from Halley's comet, depending on the assumed plasma conditions. This work brought new constraints on the distribution and preservation of volatile elements in Solar System bodies and new insights into the potential delivery mechanisms of water to Earth. The prevalence of hydrogen in larger cometary meteoroids supports models where comets could be significant contributors to Earth's volatile inventory.