Fe-C Snoek peak in iron and stony meteorites: Metallurgical and cosmological aspects

In two types of meteorites, an iron meteorite with 8% nickel (Gibeon) and a recently fallen stony meteorite (Neuschwanstein), a chondrite of class EL6, the Snoek peak in the ferritic bcc (kamacite) phase was studied by internal friction measurements. The iron meteorite shows no Snoek peak in the as-fallen state, i.e. no carbon in solid solution. This indicates an extremely low cooling rate (50 K in 106 years) in space as being characteristic of the molten cores of small planets. The Neuschwanstein meteorite shows a pronounced Snoek peak corresponding to about 0.02 wt.% carbon in solid solution. This high Fe-C Snoek peak in the ferritic phase of the chondrite meteorite indicates rapid cooling after local heating in collision with another asteroid.