Microwave Permittivity and Permeability Measurement on Lunar Soils

There has been interest in finding ways to process the lunar regolith since the early analyses of lunar samples returned from the Apollo moon missions. This fact has led to proposals for using microwaves to perform in-situ processing of the lunar soil to support future colonization of the moon. More recently, there has been speculation that the excellent microwave absorption of lunar soil came from the nanophase iron content in the regolith. The motivation for the present study was to begin obtaining a more fundamental understanding of the dielectric and magnetic properties of the regolith at microwave frequencies. A major objective of this study was to obtain information that would help answer the question about whether nanophase iron plays a major role in heating lunar soils. These new measurements over a wide frequency range can also determine the magnitude of the dielectric and magnetic absorption and if there are any resonant features that could be used to enhance processing of the regolith in the future. In addition, these microwave measurements would be useful in confirming that new simulants being developed, particularly those containing nanophase iron, would have the correct composition to simulate the lunar regolith. The results of this study suggest that nanophase iron does not play a major role in heating lunar regolith.