Investigation Of The Electromagnetic Properties Of Magnetite As A Function Of Grain Size

Ground-penetrating radar (GPR) can be used to find subsurface water on Mars. The electromagnetic properties of the soil, specifically dielectric permittivity and magnetic permeability, strongly affect the depth of penetration of GPR. Attenuation of electromagnetic waves is higher in soils with high magnetic permeability and dielectric permittivity values. Previous research suggests that the electromagnetic properties of magnetite, a mineral present in the global Martian dust layer, may vary with grain size at low frequencies. In this paper these properties were measured at radar frequencies to determine whether grain size will affect GPR. The measurements indicated that grain size has an effect on these properties. Dielectric permittivity decreased with decreasing grain size, while magnetic permeability increased with decreasing grain size. The time constant of the magnetic relaxation also increases with decreasing grain size. The<br>changes in dielectric permittivity are small and will have little effect on GPR results. However, the changes in magnetic permeability and the time constant of magnetic relaxation will have a larger effect. These results indicate that grain size should be taken into account when interpreting GPR data obtained on Mars.