Transmission of a Seismic Wave Generated by Impacts on Granular Asteroids

In this paper, we use a soft-sphere discrete element method code to simulate the transmission and study the attenuation of a seismic wave. Then, we apply our findings to the different space missions that have had to touch the surface of different small bodies in the solar system. Additionally, we do the same in regard to the seismic wave generated by the hypervelocity impacts produced by the DART and Hayabusa2 missions once the shock wave transforms into a seismic wave. We find that even at very low pressures, such as those present in the interior of asteroids, the seismic wave speed can still be on the order of hundreds of meters per second depending on the velocity of the impact that produces the wave. As expected from experimental measurements, our results show that wave velocity is directly dependent on P (1/6), where P is the total pressure (confining pressure plus wave-induced pressure). Regardless of the pressure of the system and the velocity of the impact (in the investigated range), energy dissipation is extremely high. These results provide us with a way to anticipate the extent to which a seismic wave could have been capable of moving some small particles on the surface of a small body upon contact with a spacecraft. Additionally, this rapid energy dissipation would imply that even hypervelocity impacts should perturb only the external layer of a self-gravitating aggregate on which segregation and other phenomena could take place. This would, in turn, produce a layered structure of which some evidence has been observed.

Automated summary

In this paper, a soft-sphere discrete element method code is used to simulate the transmission and study the attenuation of a seismic wave. The results are then applied to different space missions and impacts on small bodies in the solar system. The findings show that the seismic wave speed is directly dependent on the velocity of the impact and the total pressure. It is also observed that energy dissipation is high regardless of the pressure and impact velocity. These findings provide insights into the movement of particles on the surface of small bodies and the potential effects of hypervelocity impacts.