Science and Exploration

Iron Rain: Measuring The Occurrence Rate And Origin Of Small Iron Meteoroids At Earth

By Keith Cowing
Press Release
September 21, 2021
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Iron Rain: Measuring The Occurrence Rate And Origin Of Small Iron Meteoroids At Earth
Density of iron-like meteors, binned by accumulated energy per area and velocity. Plotted meteors have F parameters of less than 0.31 and luminous trajectories shorter than 9 km. An energy per area line of ?S = 4 MJm?2 for vertical entry is plotted in green, under which are the majority of iron candidates meeting our trail length and F parameter criteria.

We report results of a four-year survey using Electron Multiplied Charged Coupled Device (EMCCD) cameras recording 34761 two-station video meteor events complete to a limiting magnitude of +6.
The survey goal was to characterize probable iron meteoroids. Using only physical properties of the meteor trajectories including early peaking light curves, short luminous trajectories, and high energies accumulated per area at beginning, we identified 1068 iron meteors. Our iron candidates are most abundant at slow speeds < 15 km/s, where they make up approximately 20% of the mm-sized meteoroid population. They are overwhelmingly on asteroidal orbits, and have particularly low orbital eccentricities and smaller semi-major axes when compared to non-irons between 10-20 km/s. Our iron population appears to be more numerous at fainter magnitudes, comprising 15% of slow (10-15 km/s) meteors with peak brightness of +3 with the fraction rising to 25% at +6 to +7, our survey limit. The iron orbits are most consistent with an asteroidal source and are in highly evolved orbits, suggesting long collisional lifetimes (107 years). Metal-rich chondrules (nodules) found in abundance in EL Chondrites are one possible source for this population. We also propose a possible technique using R-band colours to more robustly identify fainter iron meteors with very high confidence. Tristan Mills, P. G. Brown, M. J. Mazur, D. Vida, Peter S. Gural, Althea V. Moorhead Comments: Accepted for publication in MNRAS on September 21st, 2021. 13 pages, 21 figures Subjects: Earth and Planetary Astrophysics (astro-ph.EP) Cite as: arXiv:2109.10265 [astro-ph.EP] (or arXiv:2109.10265v1 [astro-ph.EP] for this version) Submission history From: Tristan Mills [v1] Tue, 21 Sep 2021 15:46:13 UTC (9,749 KB)

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