Core solidification and dynamo evolution in a mantle-stripped planetesimal

A. Scheinberg, L. T. Elkins-Tanton, G. Schubert and D. Bercovici

Journal of Geophysical Research: Planets
Article first published online: 5 JAN 2016 | DOI: 10.1002/2015JE004843


“The physical processes active during the crystallization of a low-pressure, low-gravity planetesimal core are poorly understood but have implications for asteroidal magnetic fields and large-scale asteroidal structure. We consider a core with only a thin silicate shell, which could be analogous to some M-type asteroids including Psyche, and use a parameterized thermal model to predict a solidification timeline and the resulting chemical profile upon complete solidification. We then explore the potential strength and longevity of a dynamo in the planetesimal’s early history. We find that cumulate inner core solidification would be capable of sustaining a dynamo during solidification, but less power would be available for a dynamo in an inward dendritic solidification scenario. We also model and suggest limits on crystal settling and compaction of a possible cumulate inner core.