Thermomagnetic properties, natural magnetic moments, and magnetic anisotropies of some chondritic meteorites

Thermomagnetic analyses, thermal demagnetization of natural and laboratory-induced remanent magnetic moments, and measurements of magnetic anisotropy have been carried out on a number of chondritic stony meteorites. Eighty to ninety per cent of the saturation magnetic moments were due to α-phase iron-nickel (kamacite) containing 5 to 6 per cent of nickel, and this phase was also responsible for most of the observed remanence and magnetic anisotropy. Minor magnetic constituents were determined with much less certainty. The natural magnetic moments of the Mt. Browne, Homestead, and Farmington chondrites had two components of quite different origins; in each case the important component appears to have been induced thermally in an extraterrestrial field. The Mokoia carbonaceous chondrite was found to have only a small moment, consistent with isothermal induction in the earth's field. The magnetic anisotropies of eight chondrites were found to be related to the degree of metamorphism indicated by their porosities. The magnetic evidence is consistent with the supposition that the chondrites once formed parts of the mantle of a body with a fluid metal core which produced a magnetic field of terrestrial type.