Numerical simulation and ground-penetrating radar response analysis of lunar lava tubes

Lava tubes are considered prime candidates for future lunar habitats. However, their identification using Ground Penetrating Radar remains constrained by interpretative frameworks largely derived from high-loss terrestrial analog environments. This study employs two-dimensional Finite-Difference Time-Domain simulations at a center frequency of 60 MHz to systematically investigate the Ground Penetrating Radar response of lunar lava tubes and to contrast these responses with those from terrestrial analog models, thereby elucidating the role of dielectric environments in shaping radar signatures. The results reveal a fundamental divergence between the two settings. In terrestrial environments, high electrical conductivity acts as a low-pass filter that strongly suppresses deep reflections. In contrast, the low-loss lunar environment permits efficient electromagnetic wave propagation. In particular, lunar models exhibit pronounced surface-to-ceiling multiple reflections whose amplitudes are approximately two orders of magnitude greater than those observed in terrestrial models at comparable depths. We argue that these multiple reflections, traditionally treated as noise in terrestrial radar interpretation, constitute critical kinematic indicators of intact subsurface void structures. The presence of pronounced multiple reflections implies smooth interfaces and minimal scattering, thereby offering a diagnostic indicator for assessing the structural stability of lava tubes for potential future utilization.