Frequency and temperature dependence in electromagnetic properties of Martian analog minerals

Abstract

Ground‐penetrating radar (GPR) has the potential to image the Martian subsurface to give geological context to drilling targets, investigate stratigraphy, and locate subsurface water. GPR depth of penetration depends strongly on the electromagnetic (EM) properties (complex dielectric permittivity, complex magnetic permeability, and DC resistivity) of the subsurface. These EM properties in turn depend on the mineralogical composition of the subsurface and are sensitive to temperature. In this study, the EM properties of Martian analog samples were measured versus frequency (1 MHz‐1 GHz) and at Martian temperatures (180–300 K). Results from the study found the following: gray hematite has a large temperature‐dependent dielectric relaxation, magnetite has a temperature‐independent magnetic relaxation, and JSC Mars‐1 has a broad temperature‐dependent dielectric relaxation most likely caused by absorbed water. Two orbital radars, MARSIS and SHARAD, are currently investigating the subsurface of Mars. On the basis of the results of our measurements, the attenuation rate of gray hematite is 0.03 and 0.9 dB/m, magnetite is 0.04 and 1.1 dB/m, and JSC Mars‐1 is 0.015 and 0.09 dB/m at MARSIS and SHARAD frequencies, respectively, and at the average Martian temperature of 213 K. With respect to using GPR for subsurface investigation on Mars, absorbed water will be a larger attenuator of radar energy as high concentrations of magnetite and gray hematite are not found globally on Mars.