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

¹ Department of Physics and Astronomy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea
² SNU Astronomy Research Center, Department of Physics and Astronomy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea
³ Korea Astronomy and Space Science Institute (KASI), 776 Daedeok-daero, Yuseong-gu, Daejeon 34055, Republic of Korea

^★ Corresponding authors: sjin@kasi.re.kr; ishiguro@snu.ac.kr

Received: 6 June 2025
Accepted: 8 September 2025

Abstract

Context. The surface of asteroid (25143) Itokawa shows both fresh and mature terrains, despite its short space-weathering timescale of approximately 10³ years, as inferred from recent studies. Seismic shaking triggered by the impact that formed the 8-meter crater Kamoi has been proposed as a possible explanation for the diversity.

Aims. This study aims to examine whether the seismic shaking induced by the impact might account for the observed spatial variations in space weathering and might further constrain the internal structure of Itokawa.

Methods. 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.

Results. 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 × 10⁻⁸ to 5.0 × 10⁻⁷, implying that the interior of Itokawa contains blocks tens of meters across and acts as a strongly scattering medium.

Conclusions. Our findings provide unique dynamical evidence, based on seismic wave propagation modeling, that supports the hypothesis that the interior of Itokawa truly is a rubble pile.