The properties of cm–sized iron meteoroids

Vojáček, Vlastimil; Borovička, J.; Spurný, Pavel; Čapek, D.

doi:10.1016/j.pss.2020.104882

Cited by 12 publications

(12 citation statements)

References 17 publications

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“…All of them are of type I according to the classification of Ceplecha and McCrosky (1976) and were therefore produced by stony meteoroids, most probably ordinary chondrites. We cannot exclude presence of enstatite chondrites or some strong achondrites but the presence of carbonaceous chondrites, which typically belong to type II, is unlikely, and irons, which belong to type III (Vojáček et al 2020), can be excluded. On statistical basis, 13 of the 14 type I fireballs should be ordinary chondrites, since from ordinary and enstatite chondrites and achondrites, ordinary chondrites form 93% of meteorite falls.…”

Section: Additional Fireballsmentioning

confidence: 96%

Two Strengths of Ordinary Chondritic Meteoroids as Derived from their Atmospheric Fragmentation Modeling

Borovička,

Spurný,

Shrbený

2020

Preprint

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The internal structure and strength of small asteroids and large meteoroids is poorly known. Observation of bright fireballs in the Earth's atmosphere can prospect meteoroid structure by studying meteoroid fragmentation during the flight. Earlier evaluations showed that meteoroid strength is significantly lower than that of the recovered meteorites. We present detailed study of atmospheric fragmentation of seven meteorite falls, all ordinary chondrites, and 14 other fireballs, where meteorite fall was predicted but the meteorites, probably also ordinary chondrites, were not recovered. All observations were made by the autonomous observatories of the European Fireball Network and include detailed radiometric light curves. A model, called the semi-empirical fragmentation model, was developed to fit the light curves and decelerations. Videos showing individual fragments were available in some cases. The results demonstrated that meteoroids do not fragment randomly but in two distinct phases. The first phase typically corresponds to low strengths of 0.04 -0.12 MPa. In 2/3 of cases, the first phase was catastrophic or nearly catastrophic with at least 40% of mass lost. The second phase corresponds to 0.9 -5 MPa for confirmed meteorite falls and to somewhat lower strengths, from about 0.5 MPa for smaller meteoroids. All these strengths are lower than tensile strengths of ordinary chondritic meteorites cited in the literature, 20 -40 MPa. We interpret the second phase as being due by cracks in meteoroids and the first phase as separation of weakly cemented fragments, which reaccumulated at surfaces of asteroids after asteroid collisions.

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Section: Additional Fireballsmentioning

confidence: 96%

Two Strengths of Ordinary Chondritic Meteoroids as Derived from their Atmospheric Fragmentation Modeling

Borovička,

Spurný,

Shrbený

2020

Preprint

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“…This can be partly a selection effect because asteroids with high-inclination orbits have a lower probability of being discovered (Tricarico 2017). Of the nine centimeter-sized iron meteoroids identified by Vojáček et al (2020), three had high inclinations from 30 • to 70 • . The silicate absorption band in the dust spectrum excludes the possibility that the Bering Sea asteroid was an iron object, however.…”

Section: Discussionmentioning

confidence: 99%

Satellite observation of the dust trail of a major bolide event over the Bering Sea on December 18, 2018

Borovička

Setvák

Roesli³

et al. 2020

A&A

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Context. One of the most energetic bolide events in recent decades was detected by the US Government sensors (USGS) over remote areas of the Bering Sea on December 18, 2018, 23:48 UT. No ground-based optical observations exist. Aims. Using the satellite imagery of the dust trail left behind by the bolide, we tried to reconstruct the bolide trajectory. In combination with the bolide speed reported by the USGS, we computed the pre-atmospheric orbit. Observations in various spectral bands from 0.4 to 13.3 μm enabled us to study the dust properties. Methods. Images of the dust trail and its shadow obtained from various angles by the Multi-angle Imaging SpectroRadiometer (MISR) on board the Terra polar satellite and geostationary satellites Himawari-8 and Geostationary Operational Environmental Satellite 17 (GOES-17) were used. The initial position and orientation of the trail was varied, and its projections into the geoid coordinate grid were computed and compared with real data. Trail motion due to atmospheric wind was taken into account. Radiances and reflectances of selected parts of the dust trail were taken from the Moderate-resolution Imaging Spectroradiometer (MODIS) on board Terra. Reflectance spectra were compared with asteroid spectra. Results. The bolide radiant was found to be 13° ± 9° from that reported by the USGS, at azimuth 130° (from south to west) and zenith distance 14°. The bolide position was confirmed, including the height of maximum dust deposition around 25 km. The incoming asteroid had to be quite strong to maintain a high speed down to this height. The speed of 32 km s−1, reported by the USGS, was found to be plausible. The orbit had a high inclination of about 50° and a perihelion distance between 0.95–1 AU. The semimajor axis could not be restricted well but was most probably between 1–3 AU. The dust reflectance was much lower in the blue than in the red, consistent with the material of A- or L-type asteroid. The absorption at 11 μm confirms the presence of crystalline silicates in the dust.

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“…This can be partly a selection effect because asteroids with high-inclination orbits have a lower probability of being discovered (Tricarico 2017). Of the nine centimeter-sized iron meteoroids identified by Vojáček et al (2020) asteroid was an iron object, however. The strong decrease in reflectance from red to blue wavelengths suggests that the material was similar to that of asteroids of rare spectral types A or L. A-type asteroids are dominated by olivine and account for less than 0.16% of all main-belt objects larger than 2 km (DeMeo et al 2019).…”

Section: Discussionmentioning

confidence: 99%

Satellite observation of the dust trail of a major bolide event over the Bering Sea on December 18, 2018

Borovicka,

Setvak,

Roesli

et al. 2020

Preprint

View full text Add to dashboard Cite

Context. One of the most energetic bolide events in recent decades was detected by the US Government sensors (USGS) over remote areas of the Bering Sea on December 18, 2018, 23:48 UT. No ground-based optical observations exist. Aims. Using the satellite imagery of the dust trail left behind by the bolide, we tried to reconstruct the bolide trajectory. In combination with the bolide speed reported by the USGS, we computed the pre-atmospheric orbit. Observations in various spectral bands from 0.4 µm to 13.3 µm enabled us to study the dust properties. Methods. Images of the dust trail and its shadow obtained from various angles by the Multi-angle Imaging SpectroRadiometer (MISR) on board the Terra polar satellite and geostationary satellites Himawari-8 and Geostationary Operational Environmental Satellite 17 (GOES-17) were used. The initial position and orientation of the trail was varied, and its projections into the geoid coordinate grid were computed and compared with real data. Trail motion due to atmospheric wind was taken into account. Radiances and reflectances of selected parts of the dust trail were taken from the Moderate-resolution Imaging Spectroradiometer (MODIS) on board Terra. Reflectance spectra were compared with asteroid spectra. Results. The bolide radiant was found to be 13 • ± 9 • from that reported by the USGS, at azimuth 130 • (from south to west) and zenith distance 14 • . The bolide position was confirmed, including the height of maximum dust deposition around 25 km. The incoming asteroid had to be quite strong to maintain a high speed down to this height. The speed of 32 km s −1 , reported by the USGS, was found to be plausible. The orbit had a high inclination of about 50 • and a perihelion distance between 0.95-1 AU. The semimajor axis could not be restricted well but was most probably between 1-3 AU. The dust reflectance was much lower in the blue than in the red, consistent with the material of A-or L-type asteroid. The absorption at 11 µm confirms the presence of crystalline silicates in the dust.

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The properties of cm–sized iron meteoroids

Cited by 12 publications

References 17 publications

Two Strengths of Ordinary Chondritic Meteoroids as Derived from their Atmospheric Fragmentation Modeling

Two Strengths of Ordinary Chondritic Meteoroids as Derived from their Atmospheric Fragmentation Modeling

Satellite observation of the dust trail of a major bolide event over the Bering Sea on December 18, 2018

Satellite observation of the dust trail of a major bolide event over the Bering Sea on December 18, 2018

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