Article Abstract:
There are large uncertainties involved in measurements of the flux of micrometeoroids due to the destruction of particles by weathering, poor age constraint, low particle counts or inefficient magnetic collection or separation techniques. The collection of thousands of preserved and dated micrometeorites from the bottom of the South Pole water well attempts to resolve those problems. Precise estimates of flux and mass distribution for 50-700 mum melted micrometeorites were determined, and results suggest that around 90% of incoming submillimetre particles evaporate during atmospheric entry.
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Article Abstract:
The average oceanic-mantle Os/Ir ratio cannot be distinguished from that in the Cl-type carbonaceous chondrites. However, ratios of Ru/Ir, Pt/Ir and Pd/Ir are around 40% higher. It is possible that mixing of differentiated outer-core material back into the mantle following core separation is the explanation for the observed noble-metal ratios. Evidence from this work tends to support the view that deep-seated mantle plumes account for all or most of the upward convective mass transfer in the mantle.
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Article Abstract:
Laboratory experiments on thermochemical convection with a fluid with stratified density and viscosity indicate that even small chemical heterogeneities can totally change the style of convection when the material is heterogeneous in both viscosity and density. This research gives an insight into the forms that convection may take if Earth's mantle is chemically heterogeneous. It is likely that thermochemical convection has a significant impact on the dynamics of the core.
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