Breakup and Structure of an H-Chondrite Parent Body: The H-Chondrite Flux over the Last Million Years

Benoit, P. H.; Sears, D. W. G.

doi:10.1006/icar.1993.1017

Cited by 27 publications

(8 citation statements)

References 12 publications

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“…Should we expect to see a match between the observed meteorites in the terrestrial collection and the relative abundance of petrologic types in the undisrupted parent body? Finding a match would be fortuitous, given that the Earth's meteorite flux is believed to have changed over time (Benoit and Sears 1993) and if the parent body underwent partial disintegration, the lower petrologic types near the surface should be preferentially ejected (compared to higher petrologic types located in the interior of the body).…”

Section: Resultsmentioning

confidence: 99%

Importance of the accretion process in asteroid thermal evolution: 6 Hebe as an example

Ghosh

Weidenschilling

McSween

2003

Meteorit & Planetary Scien

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Importance of the accretion process in asteroid thermal evolution:6 Hebe as an example Abstract-Widespread evidence exists for heating that caused melting, thermal metamorphism, and aqueous alteration in meteorite parent bodies. Previous simulations of asteroid heat transfer have assumed that accretion was instantaneous. For the first time, we present a thermal model that assumes a realistic (incremental) accretion scenario and takes into account the heat budget produced by decay of 26 Al during the accretion process. By modeling 6 Hebe (assumed to be the H chondrite parent body), we show that, in contrast to results from instantaneous accretion models, an asteroid may reach its peak temperature during accretion, the time at which different depth zones within the asteroid attain peak metamorphic temperatures may increase from the center to the surface, and the volume of high-grade material in the interior may be significantly less than that of unmetamorphosed material surrounding the metamorphic core. We show that different times of initiation and duration of accretion produce a spectrum of evolutionary possibilities, and thereby, highlight the importance of the accretion process in shaping an asteroid's thermal history. Incremental accretion models provide a means of linking theoretical models of accretion to measurable quantities (peak temperatures, cooling rates, radioisotope closure times) in meteorites that were determined by their thermal histories.

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Section: Resultsmentioning

confidence: 99%

Importance of the accretion process in asteroid thermal evolution: 6 Hebe as an example

Ghosh

Weidenschilling

McSween

2003

Meteorit & Planetary Scien

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“…Relevant insight in this context may be also provided by evidence from meteorite types, thermal histories, Argon-Argon and cosmicrays exposure ages, as well as from comparisons between the Antarctic and non-Antarctic collections (which record different average fall times). For instance, Benoit and Sears (1993) have recently found indications that the flux of H-chondrites has significantly changed in the last several hundred thousand years. As for the cratering fluxes onto the Earth, the other inner planets and the Moon, our results indicate that significant (up to an order of magnitude) peaks over the 0.1 to 1 Myr time scales are possible from time to time.…”

Section: Discussionmentioning

confidence: 99%

The main belt as a source of near-Earth asteroids

1996

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We investigate the flux of main-belt asteroid fragments into resonant orbits converting them into near-Earth asteroids (NEAs), and the variability of this flux due to chance interasteroidal collisions. A numerical model is used, based on collisional physics consistent with the results of laboratory impact experiments. The assumed main-belt asteroid size distribution is derived from that of known asteroids extrapolated down to sizes of S 40 cm, modified in such a way to yield a quasi-stationary fragment production rate over times ZZ 100 Myr. The results show that the asteroid belt can supply a few hundred km-sizedNEAs per year, well enough to sustain the current population of such bodies. On the other hand, if our collisional physics is correct, the number of existing IO-km objects implies that these objects either have very long-lived orbits, or must come from a different source (i.e., comet,s). Our model predicts that the fragments supplied from the asteroid belt have initially a power-law size distribution somewhat steeper than the observed one, suggesting preferential removal of small objects. The component of t$he NEA population with dynamical lifetimes shorter than or of the order of 1 Myr can vary by a factor reaching up to a few tens, due to single large-scale collisions in the main belt; these fluctuations are enhanced for smaller bodies and faster evolutionary time scales. As a consequence, the Earth's cratering rate can also change by about an order of ma.gnitude over the 0.1 to 1 Myr time scales. Despite these sporadic spikes, when averaged over times of 10 Myr or longer the fluctuat,ions are unlikely to exceed a factor two.

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“…lb). In our original study, all members of the unusual subgroup were petrologic type 5 (Benoit and Sears, 1992), but Benoit and Sears (1993a) noted the presence of H4 and H6 chondrites in the unusual subgroup, although cosmic-ray exposure data were not available.…”

Section: The H4 and H6 Chondritesmentioning

confidence: 94%

Rapid changes in the nature of the H chondrites falling to Earth

Benoit

Sears

1996

Meteorit & Planetary Scien

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Abstract-We have previously identified a subgroup of Antarctic H chondrites that are significantly different from H chondrites among the modem falls in terms of induced thermoluminescence (TL), metallographic cooling rate, and cosmogenic inert gas contents. Here we examine their terrestrial and thermal history as apparent in their natural TL and radioactive cosmogenic isotope abundances. These meteorites have a tendency towards high 26A1 activities and fairly short 14C and 36Cl terrestrial ages (generally 1.2 AU to -1 AU within the last

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Breakup and Structure of an H-Chondrite Parent Body: The H-Chondrite Flux over the Last Million Years

Cited by 27 publications

References 12 publications

Importance of the accretion process in asteroid thermal evolution: 6 Hebe as an example

Importance of the accretion process in asteroid thermal evolution: 6 Hebe as an example

The main belt as a source of near-Earth asteroids

Rapid changes in the nature of the H chondrites falling to Earth

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