Seismic Efficiency for Simple Crater Formation in the Martian Top Crust Analog

The first seismometer operating on the surface of another planet was deployed by the NASA InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission to Mars. It gives us an opportunity to investigate the seismicity of Mars, including any seismic activity caused by small meteorite bombardment. Detectability of impact generated seismic signals is closely related to the seismic efficiency, defined as the fraction of the impactor's kinetic energy transferred into the seismic energy in a target medium. This work investigated the seismic efficiency of the Martian near surface associated with small meteorite impacts on Mars. We used the iSALE‐2D (Impact‐Simplified Arbitrary Lagrangian Eulerian) shock physics code to simulate the formation of the meter‐size impact craters, and we used a recently formed 1.5 m diameter crater as a case study. The Martian crust was simulated as unfractured nonporous bedrock, fractured bedrock with 25% porosity, and highly porous regolith with 44% and 65% porosity. We used appropriate strength and porosity models defined in previous works, and we identified that the seismic efficiency is very sensitive to the speed of sound and elastic threshold in the target medium. We constrained the value of the impact‐related seismic efficiency to be between the order of ∼10‐7 to 10‐6 for the regolith and ∼10‐4 to 10‐3 for the bedrock. For new impacts occurring on Mars, this work can help understand the near‐surface properties of the Martian crust, and it contributes to the understanding of impact detectability via seismic signals as a function of the target media. Plain Language Summary Impact cratering is a common geological process on solid planetary bodies. When impact occurs, it releases shock waves into the target medium. The impactor's kinetic energy is spent on internal energy change (heating), plastic (irreversible) and elastic (reversible) deformation in the target. Seismic efficiency describes how much of the impact's kinetic energy is transferred into seismic energy. Having estimates for the values of the seismic efficiency in such events can help in further describing the properties of the Martian surface, particularly if impact conditions are known. In this work, we are using the iSALE‐2D (Impact‐Simplified Arbitrary Lagrangian Eulerian) shock physics code to simulate meter‐size crater formation on Mars. Our results show that the pressure wave behaves differently in different target properties. Th