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| Titel |
The efficiency of magma heat transport in accreting planetesimals |
| VerfasserIn |
Wladimir Neumann, Doris Breuer, Tilman Spohn |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250056446
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| Zusammenfassung |
| Compositional differences between meteorites have been interpreted as being indicative of
wide variations in the degree of differentiation of their parent bodies (planetesimals).
Differentiated planetesimals must have undergone (partial) melting which suggests that
melting was a wide-spread phenomenon in the early solar system. The heat sources that have
been suggested to be capable of providing sufficient thermal energy to the planetesimal are
the decays of the short lived nuclides 26Al and 60Fe. Thermal models have shown that
planetesimals may experience differing degrees of partial melting depending on the onset
time of accretion relative to the time of formation of the Ca-Al-rich inclusions (CAIs), the
accretion time, and the final size of the planetesimal [1]. Even the presence of a magma ocean
for these bodies has been suggested in the case of rapid accretion. One problem with these
thermal models is, however, that they assume the planetesimals to cool mainly by thermal
conduction and that they neglect the influence of magma transport on their thermal
evolution. We study numerically this processes using 1D thermal energy balance
models of an accreting body that further include magma heat transport. We have
improved the 1D thermal model of [1] by considering additionally the change of
thermal conductivity, specific heat capacity and density due to porosity, porosity loss
due to sintering, redistribution of heat sources etc. to study the influence of those
factors on the thermal evolution. The heat transport by melt segregation is modeled
assuming melt flow in porous media and by supplementing the heat conduction
equation with an advection term. This expression is calculated using the Darcy flow
equation and is valid for melt fractions large enough such that the melt forms an
interconnected network but lower than the rheological critical melt fraction. The
efficiency of the heat transport depending on the melt fraction, the permeability,
the enrichment factor of 26Al and 60Fe in the melt over the solid phase will be
discussed.
[1] Merk, R. et al. (2002) Icarus, 159, 183–191. |
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