New constraints on the magnetic history of the CV parent body and the solar nebula from the Kaba meteorite

Jérôme Gattacceca, Benjamin P. Weiss, Matthieu Gounelle

Earth and Planetary Science Letters
In Press, Corrected Proof, Available online 6 October 2016



• Kaba meteorite is a high-fidelity recorder of the CV parent body paleomagnetism.
• No stable field >0.3 μT was present 4–6 Myr after Solar System Formation (SSF).
• This indicates that the nebular field had already dissipated by this time.
• A ∼3 μT stable field was present during cooling of Kaba later than 6 Myr after SSF.
• This field was internally generated, indicating a partially differentiated parent body.”

“Recent paleomagnetic studies of Allende CV chondrite as well as thermal modeling suggest the existence of partially differentiated asteroids with outer unmelted and variably metamorphosed crusts overlying differentiated interiors. To further constrain the magnetic history of the CV parent body, we report here paleomagnetic results on Kaba CV chondrite. This meteorite contains 11 wt% pseudo-single domain magnetite, making it a rock with an excellent paleomagnetic recording capacity. Kaba appears to carry a stable natural remanent magnetization acquired on its parent body upon cooling in an internally generated magnetic field of about 3 μT3 μT from temperatures below 150 °C during thermal metamorphism about 10 to several tens of Myr after solar system formation. This strengthens the case for the existence of a molten advecting core in the CV parent body. Furthermore, we show that no significant magnetic field (i.e. lower than ∼0.3 μT∼0.3 μT) was present when aqueous alteration took place on the Kaba parent body around 4 to 6 Myr after solar system formation, suggesting a delay in the onset of the dynamo in the CV parent body and confirming that nebular fields had already decayed at that time.”