ORCID Profile
0000-0002-1243-6915
Current Organisation
University of Leeds
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Publisher: American Geophysical Union (AGU)
Date: 04-2021
DOI: 10.1029/2020JE006726
Abstract: Modeling the planetary heat transport of small bodies in the early Solar System allows us to understand the geological context of meteorite s les. Conductive cooling in planetesimals is controlled by thermal conductivity, heat capacity, and density, which are functions of temperature ( T ). We investigate if the incorporation of the T ‐dependence of thermal properties and the introduction of a nonlinear term to the heat equation could result in different interpretations of the origin of different classes of meteorites. We have developed a finite difference code to perform numerical models of a conductively cooling planetesimal with T ‐dependent properties and find that including T ‐dependence produces considerable differences in thermal history, and in turn the estimated timing and depth of meteorite genesis. We interrogate the effects of varying the input parameters to this model and explore the nonlinear T ‐dependence of conductivity with simple linear functions. Then we apply non‐monotonic functions for conductivity, heat capacity, and density fitted to published experimental data. For a representative calculation of a 250 km radius pallasite parent body, T ‐dependent properties delay the onset of core crystallization and dynamo activity by ∼40 Myr, approximately equivalent to increasing the planetary radius by 10%, and extend core crystallization by ∼3 Myr. This affects the range of planetesimal radii and core sizes for the pallasite parent body that are compatible with paleomagnetic evidence. This approach can also be used to model the T ‐evolution of other differentiated minor planets and primitive meteorite parent bodies and constrain the formation of associated meteorite s les.
Publisher: Springer Science and Business Media LLC
Date: 18-05-2011
DOI: 10.1038/NATURE10068
Abstract: The Earth's magnetic field is generated by a dynamo in the liquid iron core, which convects in response to cooling of the overlying rocky mantle. The core freezes from the innermost surface outward, growing the solid inner core and releasing light elements that drive compositional convection. Mantle convection extracts heat from the core at a rate that has enormous lateral variations. Here we use geodynamo simulations to show that these variations are transferred to the inner-core boundary and can be large enough to cause heat to flow into the inner core. If this were to occur in the Earth, it would cause localized melting. Melting releases heavy liquid that could form the variable-composition layer suggested by an anomaly in seismic velocity in the 150 kilometres immediately above the inner-core boundary. This provides a very simple explanation of the existence of this layer, which otherwise requires additional assumptions such as locking of the inner core to the mantle, translation from its geopotential centre or convection with temperature equal to the solidus but with composition varying from the outer to the inner core. The predominantly narrow downwellings associated with freezing and broad upwellings associated with melting mean that the area of melting could be quite large despite the average dominance of freezing necessary to keep the dynamo going. Localized melting and freezing also provides a strong mechanism for creating seismic anomalies in the inner core itself, much stronger than the effects of variations in heat flow so far considered.
Publisher: ACM
Date: 18-06-2021
Publisher: Wiley
Date: 24-11-2020
Publisher: Wiley
Date: 02-2021
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Jon Mound.