The recent discovery of remnant magnetizations of angrites and the CV meteorite Allende suggests that magnetic fields were generated in the iron-rich cores of their parent bodies. It has been speculated that thermal convection in a magma ocean above the iron core may have sufficiently cooled the iron-rich core to initiate thermal convection in the core and thus powered a dynamo to generate the magnetic field. The isotope chemistry of the angrites supports rapid core formation within 4 Ma after the formation of the CAIs. Such a dynamo should have lasted about 10 Ma to explain the observed magnetization. Numerical models support both possibilities. Although both classes of meteorites are similar in their magnetization, they are likely to have experienced strikingly differing differentiation histories. The magnetized CV meteorites are generally considered to be relics of metamorphic primordial crusts covering the differentiated interior of planetesimals. These crusts would be insulating and it is likely that eruptive magmatism accompanied by efficient interior cooling through magma heat transport was absent from these parent bodies. Angrites are generally considered to be relics of basaltic crusts and their formation must have invoked melt that was able to rise to the surface and efficiently cool the interior.
Figure 1: A close-up of the melt fraction in the sub-surface magma ocean of a Vesta-like body which formed at 0.5 Ma after the CAIs. Figure from: Neumann, W., Breuer, D., Spohn, T., 2013. Differentiation of Vesta: Implications for a shallow magma ocean. Submitted to EPSL.