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Updated: Jul 12, 2026

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Scattering And Absorption of Light in Planetary Regoliths
Published on: July 1, 2019
Origins for the near-Earth asteroids
Summary
Near-Earth asteroids (NEAs) are replenished by main-belt asteroids, according to new research. Physical properties of small main-belt asteroids closely resemble NEAs, supporting this origin theory.
Area of Science:
- Planetary Science
- Asteroid and Comet Research
Background:
- Near-Earth asteroids (NEAs) have short dynamical lifetimes and require replenishment.
- Two hypothesized sources for NEAs are main-belt asteroids and extinct comet nuclei.
- Distinguishing between these sources is challenging due to difficulties in measuring physical properties of small (D < 5 km) main-belt asteroids and comet nuclei.
Purpose of the Study:
- To compare the physical properties of small main-belt asteroids with those of NEAs.
- To assess the contribution of main-belt asteroids versus comet nuclei to the NEA population.
Main Methods:
- Conducted a new survey of physical properties for main-belt asteroids with diameters less than 5 kilometers.
- Analyzed spin rate and shape distributions of these main-belt asteroids.
- Compared these distributions with known data for NEAs and available data for comet nuclei.
Main Results:
- The spin rate and shape distributions of small main-belt asteroids are similar to those of NEAs.
- This similarity strongly supports a main-belt origin for the majority of NEAs.
- Analysis of limited comet nucleus data suggests that comet nuclei constitute between 0% and 40% of the total NEA population.
Conclusions:
- The physical characteristics of small main-belt asteroids are consistent with them being the primary source for replenishing near-Earth asteroids.
- The contribution of extinct comet nuclei to the NEA population is likely limited, based on current data.
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