Iron Rain: measuring the occurrence rate and origin of small iron meteoroids at Earth. (arXiv:2109.10265v1 [astro-ph.EP])

Iron Rain: measuring the occurrence rate and origin of small iron meteoroids at Earth. (arXiv:2109.10265v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Mills_T/0/1/0/all/0/1">Tristan Mills</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brown_P/0/1/0/all/0/1">P. G. Brown</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mazur_M/0/1/0/all/0/1">M. J. Mazur</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vida_D/0/1/0/all/0/1">D. Vida</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gural_P/0/1/0/all/0/1">Peter S. Gural</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Moorhead_A/0/1/0/all/0/1">Althea V. Moorhead</a>

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.

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.

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