Simulation of Impact-induced seismic shaking on asteroid (25143) Itokawa to address its resurfacing process

TL;DR

This study uses seismic wave simulations to show impact-induced shaking can explain surface variations on asteroid Itokawa, providing insights into its internal structure and resurfacing processes.

Contribution

It introduces a 3D seismic wave propagation model to assess impact effects on asteroid surface and internal structure, a novel approach for understanding asteroid resurfacing.

Findings

Seismic shaking can destabilize surface materials even at low energy levels.

Simulated boulder displacements match observed space weathering patterns.

Itokawa's interior likely contains large blocks and is a strongly scattering medium.

Abstract

The surface of asteroid (25143) Itokawa shows both fresh and mature terrains, despite its short space weathering timescale of approximately 1000 years, as inferred from recent studies. Seismic shaking triggered by the impact that formed the 8-meter Kamoi crater has been proposed as a possible explanation for the diversity. This study aims to examine whether the seismic shaking induced by the impact could account for the observed spatial variations in space weathering and further constrain the internal structure of Itokawa. Assuming that the Kamoi crater was formed by a recent impact, we conducted three-dimensional seismic wave propagation simulations and applied a simplified landslide model to estimate surface accelerations and boulder displacements. Our results show that even a low-energy case (1 % of the nominal seismic energy) produces surface accelerations sufficient to destabilize the surface materials. The simulated boulder displacements are consistent with the observed distribution of space weathering degrees even on the opposite hemisphere. We estimate the seismic diffusivity to be 1000-2000 m2 s-1 and the seismic efficiency to be in the range of 5.0 x 10-8 to 5.0 x 10-7, implying that Itokawa's interior contains blocks tens of meters across and acts as a strongly scattering medium.