A Near-Earth Object Model Calibrated to Earth Impactors

TL;DR

This study develops a debiased model of near-Earth meteoroids from 10g to 150kg, revealing size-dependent collisional lifetimes and the dominant sources of small impactors, informing planetary defense and meteoroid origin understanding.

Contribution

It introduces a new size-specific model of Earth-impacting meteoroids based on global fireball observations, extending dynamical understanding to smaller sizes than previous models.

Findings

Collisional half-life decreases from 3Myr at 0.6kg to 1Myr below this size.

Inner main belt dominates small meteoroid delivery via specific resonances.

Physical processes like thermal stresses may influence impactor populations.

Abstract

The population of Earth-impacting meteoroids and its size-dependent orbital elements are key to understanding the origin of meteorites and informing on planetary defence efforts. Outstanding questions include the role of collisions in depleting meteoroids on highly evolved orbits and the relative importance of delivery resonances. Those depend on size, with current dynamical models considering only asteroids larger than 10m in diameter. Based on 1,202 sporadic meteoroids observed by the Global Fireball Observatory, we created a debiased model of the near-Earth meteoroid population in the 10g - 150kg in size (approximately 1cm - 0.5m) as they dynamically evolved from the main asteroid belt onto Earth-crossing orbits. The observed impact population is best matched with a collisional half-life decreasing from 3Myr for meteoroids of 0.6kg (7cm) or higher, to 1Myr below this size, extending to the model lower bound of 10g. Placing our results in context with near-Earth object models for larger sizes, we find that the inner main belt continues to dominate feeding the small 1m to 10m diameter population primarily via the $\nu_6$ secular resonance and the 3:1J mean motion resonance. We also evaluated the potential significance of physical processes other than collisions on Earth-impacting meteoroids, such as low-perihelion disruptions from thermal stresses.