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| Titel |
Shallow Magma Ocean on Vesta and Implications for the HEDs |
| VerfasserIn |
Wladimir Neumann, Doris Breuer, Tilman Spohn |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250096263
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| Publikation (Nr.) |
 EGU/EGU2014-11760.pdf |
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| Zusammenfassung |
| The asteroid 4 Vesta is widely held as a differentiated object and as the parent body of the
HED meteorites. However, the origin of the HEDs, which is closely linked to the
differentiation processes, is still a subject of debate. In particular, various differentiation
scenarios have been proposed (e.g. partial melt[1] and residual melt[2,3] scenario) to explain
the process of HEDs’ formation. Here we present results of numerical calculations of the
early thermo-chemical evolution of Vesta, placing constraints on the possible differentiation
scenario and on the occurrence and depth of the Vestan mantle magma ocean. We use a
numerical heat conduction code[4] that considers accretion, compaction, melting, associated
changes of the material properties, partitioning of 26Al, advective heat transport,
differentiation by porous flow, and effective cooling of a magma ocean by convection. We
show that partitioning of 26Al and its transport with the silicate melt is crucial for the
formation of a magma ocean. Previous models that neglect this effect[5,6,7] infer a
whole-mantle magma ocean beneath a solid crust. We show that in contrast to these models a
deep magma ocean does not form if partitioning of 26Al is considered: Radioactive
nuclides are enriched in the melt and relocated towards the surface. Due to the
over-production of the radiogenic heat in a shallow layer, the melt fraction increases rapidly
above a critical melting threshold (here we assume 50 % of melt) for which the
rheology is dominated by the liquid phase, i.e. a magma ocean forms. For formation
times of Vesta |
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