Shock wave, a possible source of magnetic fields?

One possible effect due to impact cratering is the transformation of part oT the kinetic energy of the projectile to energy in the electromagnetic field. Shock-induced polarization of piezoand dielectric material could be the mechanism by which this is accomplished. Although the estimates show that the fraction of kinetic energy transformed by this mechanism is rather small, the effect could be sufficient to form some magnetic features of planets that have even a slight planetary magnetic field oT their own. The possible limits of this effect are still uncertain. The mechanism suggested is attractive because it gives a possible explanation for the high values of remanent magnetization displayed by some lunar samples, without calling for the hypothesis of a strong global magnetism for the moon in the past epochs. CRATERING IS the most prominent but probably not the most interesting effect of impacts or explosions. Other physical and chemical processes are also induced by shock waves. Results of these processes should be found during investigations of planets that have impacl-cratered surfaces. Several effects due to shock wave are well known, such as shock metamorphism, shock melting, chemical differentiation in impactites, etc. (see for example Dence, 1971; Masaytis et a/„ 1975; Parfenova and Yakovlev, 1976). One more possible effect due to impact cratering is the transformation of part of the kinetic energy of the projectile to electromagnetic energy. The possibility of the latter transformation was first recognized during the analysis of the magnetic profiling data taken by Lunokhod-2 at Le Monier area (Ivanov et al., 1976). Lunokhod-2 profiling revealed quasisinusoidal magnetic anomalies associated with impact craters with impact diameters 50-400 m (see Fig. 1). These anomalies represent the quasisinusoidal variations of magnetic field intensity around the certain level which is the local background. In searching for the mechanism of formation of these anomalies the suggestion was made that crater excavation and anomaly induction are both caused by the same phenomenon—shock wave propagation, as the result of a magnetic field impulse produced by shock-induced electric polarization in the target rocks. Shock-induced polarization can be considered as an electric current flowing through the shock wave front. This current is capable of causing some magnetic effects on adjacent materials. When a shock wave is passing through materials containing shock-polarized and ferromagnetic components, the induced elec'Schmidt Institute of Physics of the Earth. Shirshov Institute of Oceanology. Vernadsky Institute of Geochemistry and Analytical Chemistry.