Thermal evolution and sintering of chondritic planetesimals IV. Temperature dependence of heat conductivity of asteroids and meteorites

TL;DR

This study models the temperature-dependent heat conductivity of chondritic planetesimals using a phonon-based theoretical approach, incorporating mineral composition and micro-cracks, to better understand their thermal evolution.

Contribution

It introduces a comprehensive model predicting heat conductivity of chondritic materials across temperature ranges, accounting for micro-cracks and mineral mixtures, validated against meteorite data.

Findings

The model accurately reproduces experimental heat conductivity data.

Micro-cracks significantly influence the temperature dependence of heat conductivity.

Predictions cover a wide range of meteoritic compositions.

Abstract

Understanding the compaction and differentiation of the planetesimals and protoplanets from the Asteroid Belt and the terrestrial planet region of the Solar System requires a reliable modeling of their internal thermal evolution. An important ingredient for this is a detailed knowledge of the heat conductivity of the chondritic mixture of minerals and metal in planetesimals. The temperature dependence of the heat conductivity is evaluated here from the properties of its mixture components by a theoretical model. This allows to predict the temperature dependent heat conductivity for the full range of observed meteoritic compositions and also for possible other compositions. For this purpose, published results on the temperature dependence of heat conductivity of the mineral components found in chondritic material are fitted to the model of Callaway for heat conductivity in solids by phonons. For the Ni,Fe-alloy published laboratory data are used. The heat conductivity of chondritic material then is calculated by means of mixing-rules. The role of micro-cracks is studied which increase the importance of wall-scattering for phonon-based heat conductivity. The model is applied to published data on heat conductivity of individual chondrites. The experimental data for the dependence of the heat conductivity on temperature can be reproduced rather well by the model if the heat conductivity is calculated for the composition of the meteorites. It is found that micro-cracks have a significant impact on the temperature dependence of the heat conductivity because of their reduction of phonon scattering length.