A time-resolved paleomagnetic record of Main Group pallasites: Evidence
for a Psyche-like parent body
Abstract
Several paleomagnetic studies have been conducted on five main group
pallasites: Brenham, Marjalahti, Springwater, Imilac and Esquel. These
pallasites have distinct cooling histories, meaning that their
paleomagnetic records may have been acquired at different times during
the thermal evolution of their parent body. Here we compile new and
existing data to present the most complete time-resolved paleomagnetic
record for a planetesimal, which includes a period of quiescence prior
to core solidification as well as dynamo activity generated by
compositional convection during core solidification. We present new
paleomagnetic data for the Springwater pallasite, which constrains the
timing of core solidification. Our results suggest that in order to
generate the observed strong paleointensities (∼ 65 - 95 μT), the
pallasites must have been relatively close to the dynamo source. Our
thermal and dynamo models predict that the main group pallasites
originate from a planetesimal with a large core (> 200 km)
and a thin mantle (< 70 km). The density of our model
large-cored planetesimals is similar to the predicted density of the
asteroid (16) Psyche. We therefore suggest that it is plausible that the
main group pallasites originated from a Psyche-like parent body. 1