| Summary: | The thermal and magnetic histories of planetesimals provide unique insights into the formation
and evolution of Earth’s building blocks. These histories can be gleaned from meteorites by
using numerical models to translate measured properties into planetesimal behaviour. In this
paper, we present a new 1D planetesimal thermal evolution and dynamo generation model. This
magnetic field generation model is the first of a differentiated, mantled planetesimal that includes
both mantle convection and sub-eutectic core solidification. We have improved fundamental
aspects of mantle heat transport by including a more detailed viscosity model and stagnant lid
convection parametrisations consistent with internal heating. We have also added radiogenic
heating from 60Fe in the metallic Fe-FeS core. Additionally, we implement a combined thermal
and compositional buoyancy flux, as well as the latest magnetic field scaling laws to predict
magnetic field strengths during the planetesimal’s thermal evolution until core solidification is
complete. We illustrate the consequences of our model changes with an example run for a 500 km
radius planetesimal. These effects include more rapid erosion of core thermal stratification and
longer duration of mantle convection compared to previous studies. The additional buoyancy
from core solidification has a marginal effect on dynamo strength, but for some initial core sulfur
contents it can prevent cessation of the dynamo when mantle convection ends. Our model can
be used to investigate the effects of individual parameters on dynamo generation and constrain
properties of specific meteorite parent bodies. Combined, these updates mean this model can
predict the most reliable and complete magnetic field history for a planetesimal to date, so is a
valuable tool for deciphering planetesimal behaviour from meteorite properties.
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