The Morávka meteorite fall: 4. Meteoroid dynamics and fragmentation in the atmosphere

Borovička, J.; Kalenda, Pavel

doi:10.1111/j.1945-5100.2003.tb00296.x

Cited by 105 publications

(104 citation statements)

References 20 publications

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“…Here ρ is atmospheric density and v is meteoroid velocity. Ordinary chondrites Morávka (Borovička & Kalenda 2003) (Borovička & Spurný 1996). However, applying the same destruction depth model as for Šumava, we found that the terminal flare would be expected at 55 km, if 2008 TC 3 were a low density (≈100 kg m −3 ) cometary body like Šumava.…”

Section: Discussionmentioning

confidence: 95%

Meteosat observation of the atmospheric entry of 2008 TC$\mathsf{_{3}}$ over Sudan and the associated dust cloud

Borovička¹,

Charvát²

2009

A&A

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We analyzed serendipitous observations by the Meteosat 8 weather satellite of the fireball caused by the entry of the small asteroid (or large meteoroid) 2008 TC 3 over northern Sudan on October 7, 2008. Meteosat 8 scans the Earth in 5 min cycles. The fireball was captured in the 2:45 UT images in four visible-near infrared channels (0.6-1.6 μm) at a height of 45 km, and in eight mid infrared channels (3.9-13.4 μm) at a height of 33 km. The latter channels also detected at least two dust clouds deposited in the atmosphere at the heights of about 44 and 36 km. The dust deposition was a result of severe atmospheric fragmentation of the asteroid, accompanied by fireball flares, which could be detected in the light scattered by the Earth's surface. The fireball brightness was measured at two random heights, 45 and 37.5 km, where it reached −18.8 and −19.7 mag, respectively. The peak brightness was probably higher than −20 mag. The color temperature of the fireball at 45 km was 3650 ± 100 K. Infrared spectra of the fresh dust clouds were dominated by the 10 μm Si-O band caused by recondensed amorphous silicates. Five minutes later, the dust clouds were detected in absorption of thermal radiation of the Earth. At that time, the silicates were largely crystalline, suggesting silicate smoke temperatures exceeding 1000 K. The total mass of the silicate smoke was estimated to be 3100 ± 600 kg. More mass was probably contained in larger, micron sized, and colder dust particles resulting from incomplete sublimation of the asteroidal material and detected later by Meteosat 8 and 9 in scattered sunlight. Based on the heights of asteroid fragmentations, we guess that the bulk porosity of 2008 TC 3 was of the order of 50%, i.e. higher than the porosity of the recovered meteorite Almahata Sitta.

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Section: Discussionmentioning

confidence: 95%

Meteosat observation of the atmospheric entry of 2008 TC$\mathsf{_{3}}$ over Sudan and the associated dust cloud

Borovička¹,

Charvát²

2009

A&A

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“…Incoming meteoroids, on the other hand, easily fragment in the atmosphere under dynamic pressures two orders of magnitude smaller than the strength of meteorites (Petrovic 2001, Popova et al, in preparation). This is valid both for cmsized (Ceplecha et al 1993) and meter sized bodies Borovička & Kalenda 2003). The typical property of stony meteoroids is therefore presence of various internal cracks, which cause structural weakness of the body.…”

Section: Properties Of Stony Meteoroidsmentioning

confidence: 92%

Properties of meteoroids from different classes of parent bodies

Borovička

2006

Proc. IAU

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Abstract. Meteoroids observed to disintegrate in the terrestrial atmosphere can be directly linked to their parent bodies in case that they belong to certain meteor showers. We present a list of two dozens of parent bodies reliably associated with well recognized meteor showers. Among the parent bodies are long period comets, Halley-type comets, Jupiter family comets, comets of the inner solar system (such as 2P/Encke) and asteroids.Physical and chemical properties of meteoroids coming from various parents are compared on the basis of meteor heights, decelerations, light curves and spectra. Jupiter family comets produce meteoroids with the lowest strength, namely porous aggregates of dust grains with bulk densities of about 0.3 g cm −3 or less. Halley type material is somewhat stronger and the material related to comet Encke is even stronger. In addition, small strong constituents, perhaps similar to carbonaceous chondrites, can be encountered within the normal cometary material. The strength of cometary material is also enhanced by long-term exposure to cosmic rays and by solar heating in the vicinity to the Sun (r < 0.2 AU). Both these processes lead to the loss of volatile sodium. Southern δ-Aquariids, Geminids and partly also Quadrantids were influenced by solar radiation. We argue that these showers, the asteroids associated with them ((3200) Phaethon and 2003 EH 1), and the whole interplanetary complexes they belong to are of cometary origin. The argument is supported by lower than chondritic Fe/Mg ratio found in Geminids as well as in Halley type comets. The typical property of stony meteoroids of asteroidal origin is the presence of internal cracks which cause that the incoming meteoroids are much weaker than the recovered meteorites.

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“…This widely held belief was based on the observed fact that stony meteorites often hit the ground in showers of fragments (e.g. Jenniskens et al 1994), video-observed meteorite falls show extensive atmospheric fragmentation (Brown et al 1994;Borovička & Kalenda 2003), and detailed numerical modeling indicated that stony meteoroids always break-up in the atmosphere (Bland & Artiemeva 2006). In this paper, we discuss the Peruvian event in the context of data gathered from well-observed fireballs and perform simple modeling of the event.…”

Section: Introductionmentioning

confidence: 99%

The Carancas meteorite impact – Encounter with a monolithic meteoroid

Borovička¹,

Spurný²

2008

A&A

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The formation of a 13-m wide impact crater by a stony meteorite near Carancas, Peru, on September 15, 2007 was an unexpected event. Stony meteoroids usually disintegrate in the atmosphere in many pieces, each landing at low velocity. We present examples of well-observed fireballs, which have all experienced atmospheric fragmentation. Using a simple model, we find that the Carancas meteoroid may have avoided fragmentation, if its strength was 20−40 MPa; such a strength would be comparable to the tensile strength of stony meteorites, but is higher than the strength of other observed meteoroids. We conclude that Carancas was a rare example of a monolithic meteoroid that was free of internal cracks. This example demonstrates that meteoroid strength can vary significantly from case to case and does not depend on meteoroid size. We estimate that the initial size of Carancas meteoroid was 0.9−1.7 m. Our model predicts an impact velocity that was in the range 2−4 km s −1 .

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The Morávka meteorite fall: 4. Meteoroid dynamics and fragmentation in the atmosphere

Cited by 105 publications

References 20 publications

Meteosat observation of the atmospheric entry of 2008 TC$\mathsf{_{3}}$ over Sudan and the associated dust cloud

Meteosat observation of the atmospheric entry of 2008 TC$\mathsf{_{3}}$ over Sudan and the associated dust cloud

Properties of meteoroids from different classes of parent bodies

The Carancas meteorite impact – Encounter with a monolithic meteoroid

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