Rapid Timescales for Magma Ocean Crystallization on the Howardite-Eucrite-Diogenite Parent Body

Asteroid 4 Vesta has long been postulated as the source for the howardite-eucrite-diogenite (HED) achondrite meteorites. Here we show that Al-free diogenite meteorites record variability in the mass-independent abundance of 26Mg (26Mg*) that is correlated with their mineral chemistry. This suggests...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2011-10, Vol.740 (1), p.L22-jQuery1323915365083='48'
Main Authors: Schiller, Martin, Baker, Joel, Creech, John, Paton, Chad, Millet, Marc-Alban, Irving, Anthony, Bizzarro, Martin
Format: Article
Language:English
Subjects:
ABUNDANCE
ACHONDRITES
ALKALINE EARTH ISOTOPES
ALUMINIUM 26
ALUMINIUM 27
ALUMINIUM ISOTOPES
ASTEROIDS
BETA DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
CRYSTALLIZATION
ELEMENT ABUNDANCE
EVEN-EVEN NUCLEI
EVOLUTION
GEOSCIENCES
ISOTOPES
LIGHT NUCLEI
MAGMA
MAGNESIUM 24
MAGNESIUM 26
MAGNESIUM ISOTOPES
METEORITES
NUCLEI
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
PHASE TRANSFORMATIONS
RADIOISOTOPES
SEAS
SECONDS LIVING RADIOISOTOPES
SOLAR SYSTEM
SOLIDIFICATION
STABLE ISOTOPES
STONE METEORITES
SURFACE WATERS
VARIATIONS
YEARS LIVING RADIOISOTOPES
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Summary:Asteroid 4 Vesta has long been postulated as the source for the howardite-eucrite-diogenite (HED) achondrite meteorites. Here we show that Al-free diogenite meteorites record variability in the mass-independent abundance of 26Mg (26Mg*) that is correlated with their mineral chemistry. This suggests that these meteorites captured the Mg-isotopic evolution of a large-scale differentiating magma body with increasing 27Al/24Mg during the lifespan of the short-lived 26Al nuclide (t 1/2 ~ 730,000 yr). Thus, diogenites and eucrites represent crystallization products of a large-scale magma ocean associated with the differentiation and magmatic evolution of the HED parent body. The 26Mg* composition of the most primitive diogenites requires onset of the magma ocean crystallization within 0.6--0.4 + 0.5 Myr of solar system formation. Moreover, 26Mg* variations among diogenites and eucrites imply that near complete solidification of the HED parent body occurred within the following 2-3 Myr. Thermal models predict that such rapid cooling and magma ocean crystallization could only occur on small asteroids (
ISSN:2041-8205
2041-8213
DOI:10.1088/2041-8205/740/1/L22