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A time-resolved paleomagnetic record of Main Group pallasites: Evidence for a Psyche-like parent body
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  • Claire Isobel O'Bryen Nichols,
  • James F J Bryson,
  • Rory D Cottrell,
  • Roger R Fu,
  • Richard J Harrison,
  • Julia Herrero-Albillos,
  • Florian Kronast,
  • John A Tarduno,
  • Benjamin P Weiss
Claire Isobel O'Bryen Nichols
University of Oxford, University of Oxford

Corresponding Author:[email protected]

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James F J Bryson
University of Oxford, University of Oxford
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Rory D Cottrell
University of Rochester, University of Rochester
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Roger R Fu
Harvard University, Harvard University
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Richard J Harrison
University of Cambridge, University of Cambridge
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Julia Herrero-Albillos
Departamento de Ciencia y Tecnología de Materiales y Fluidos, Universidad de Zaragoza, Departamento de Ciencia y Tecnología de Materiales y Fluidos, Universidad de Zaragoza and Instituto de Nanociencia y Materiales de Aragón (INMA), Universidad de Zaragoza-CSIC, Zaragoza, Spain
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Florian Kronast
Helmholtz Zentrum Berlin, Helmholtz Zentrum Berlin
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John A Tarduno
University of Rochester, University of Rochester
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Benjamin P Weiss
Massachusetts Insitute of Technology, Massachusetts Insitute of Technology
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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