GPR and EMI characterization of the hyperarid study site of Yungay, Chile: Implications of applying geophysical methods on Mars

To unequivocally discover the actual presence of life or even of near surface liquid water on extraterrestrial planetary bodies would be a key scientific breakthrough for humankind. For this reason, studying similar environments on Earth is essential to understanding the processes shaping such extraterrestrial objects. The Yungay area in the Chilean part of the Atacama Desert is deemed to be particularly suitable as a terrestrial analog of Mars (TAM). In this study, we deployed multi-frequency ground penetrating radar (GPR) and a six-coil electromagnetic induction (EMI) system with a maximum depth of investigation of 1.8 m over an area of 0.66 hectares (110 x 60 m). By applying a LOWESS algorithm to the GPR envelope data, we aimed to extrapolate the strongest amplitudes indicating physical contrasts to 3D. The results were constrained with two existing pits 100 m apart. Whereas clay content was mostly responsible for GPR signal attenuation, changes in texture and stratigraphy were linked with strong amplitude reflections. EMI showed very low apparent electrical conductivity (ECa) values between 0 and 5 mS/m. The ECa variability could be linked to changes in clay content with depth. This agreed with the surface obtained from the LOWESS algorithm. Although soil samples are still necessary to constrain the measured signals, we showed the benefits of applying geophysics for large-scale characterization and can conclude that these two methods are suitable for such hyperarid TAM environments. A similar routine if applied on the surface of Mars could deliver promising results for similar characteristics