Laboratory investigation into the dielectric properties of a L-chondrite (NWA 12857)

Abstract

Ground Penetrating Radar (GPR) is a terrestrial geophysical exploration method that has recently become one of the most promising technique for planetary, asteroidal and cometary subsurface exploration. The capability of GPR to sound Solar System's bodies relies on the electromagnetic properties of the constitutive materials. Enstatite and ordinary chondrites represent class of asteroids occurring in the inner asteroid belt whereas carbonaceous chondrites and their icy mixtures are reasonable analogues for cometary material as well as constituent of shallow part of some Jovian satellite crusts. Therefore, the knowledge of electromagnetic properties of meteorites is very important because it allows to estimate the radar response in terms of signal velocity and attenuation. In this work we measured the real and imaginary parts of the permittivity of a L5 chondrite meteorite as a function of frequency (20 Hz-1 MHz) by using a capacitive cell connected to a self-balancing bridge. We studied the spatial variability of dielectric properties of the sample that exhibits areas with different textures characterized by a darker appearance. In general, the meteorite sample shows a stronger dispersive behavior compared to terrestrial rocks with higher values for both real and imaginary part of permittivity. In particular, the occurrence of very small grains (<10 μm) of FeNi metal, troilite and chromite scattered in some areas of the meteorite seems to be the cause of such behavior.