Low-velocity impact response of lunar and Martian regolith simulants: Implications for lunar and Martian surface explorations

The granular mechanics of lunar and Martian regolith remain inadequately understood, impeding progress in successful exploration, landing, drilling, sampling, and construction activities on extraterrestrial surfaces. This study aims to bridge this knowledge gap by investigating the granular behavior of the lunar and Martian regolith under impact conditions. Impact cratering experiments were conducted for the lunar highlands, lunar mare, Martian regolith simulants (LHS-1, LMS-1, and MGS-1, respectively), and terrestrial silica sand with similar particle sizes as target granular materials, with a sphere projectile dropping at low velocities. A systematic analysis was undertaken to elucidate the influence of parameters, including the fall height of the projectile, impact velocity, kinetic energy of the projectile, porosity, cohesion, and internal friction angle, on the resulting crater depths. Our findings demonstrate that the crater depths of regolith layers of the lunar highlands and Martian surfaces are greater than those of the lunar mare regolith and terrestrial silica sand layers. For example, the crater depth of the lunar highland regolith layer is about two times greater than that of the terrestrial silica sand layer at an impact velocity of 40–70 cm/s. Additionally, our power-law scaling highlights less resistance to crater impact in the lunar and Martian regolith layers than in the terrestrial sand layer. Our study highlights a significant difference in granular behavior between the Earth's sand layer and the lunar and Martian regolith layers, providing valuable insights for future exploration, coring, drilling, and resource utilization endeavors on the lunar and Martian surfaces.