Primitive Achondrite Paleomagnetism

Meteorites are typically divided into three distinct types: chondrites, which are unmelted accretion aggregates; achondrites, which form as the result of melting and differentiation on their parent bodies; and primitive achondrites, which come from bodies that were partially melted. Primitive achondrites provide a unique window into planetary evolution by allowing us to study how early solar system bodies transformed from pristine nebular material into radially-layered bodies like the Earth. 

Acapulcoites and Lodranites are two meteorites groups that are thought to have formed on the same parent body. These unique meteorites show evidence for partial melting, with some samples even containing mm- to cm-scale metal veins that might have been traveling to an ancient core (see top image)! To determine if the parent body had a sizable metal core, we conducted a paleomagnetic investigation of Acapulco, the eponymous meteorite of the Acapulcoite group. The presence of a remanent magnetization indicated of formation in an ancient field would provide direct evidence that the parent body had a core. This can help us constrain the formation times of cores on small bodies and determine if unmelted and melted meteorites could come from the same parent body. This study included a paleomagnetic analysis on bulk samples and on individual, metal-bearing olivine and pyroxene grains. This is the first paleomagnetic study of a primitive achondrite, and the results are published in Mansbach et al 2023.