Segregation on small rubble bodies due to impact-induced seismic shaking

TL;DR

This paper develops a framework to analyze how impact-induced seismic shaking causes regolith segregation on small rubble-pile asteroids, combining impact modeling, stochastic collisional history, and discrete element simulations.

Contribution

It introduces a comprehensive framework linking impact seismicity to regolith segregation on rubble-pile asteroids, incorporating impact modeling, stochastic impact history, and granular simulations.

Findings

Seismic shaking can drive size segregation on rubble-pile asteroids.

Segregation effectiveness depends on impact energy, location, wave speed, and seismic diffusivity.

Impact-driven seismicity is sufficient to cause regolith segregation.

Abstract

We present a framework to study regolith segregation on rubble-pile asteroids (self-gravitating granular aggregates) due to seismic shaking induced by impacts sustained during their lifetimes. We first relate the amplitude and frequency of surface vibrations to the location and severity of an impact, and the rubble body's geometry and bulk properties. For clarity, the body is taken to be an ellipsoid with size and spin close to that of Itokawa, although other asteroids are also easily incorporated. We then model the body's collisional history stochastically given the variability in the impact activity on an asteroid. Finally, we utilize discrete element simulations to investigate the regolith's response to impacts. In these simulations, in any sample collisional history, every time an impact occurs, a bin filled with a grain mixture and located at the region of interest on the asteroid is vibrated at that impact's associated amplitude and frequency. Utilizing this framework we find that impact-driven seismicity is sufficient to drive size segregation on small rubble-piles, but the segregation quality depends on several aspects, e.g. total impact energy supplied, placement of the region of interest, bulk wave speed, and seismic diffusivity.