Estimation of space weathering timescale on (25143) Itokawa: Implications on its rejuvenation process

TL;DR

This study estimates the space weathering timescale on asteroid Itokawa's surface to be around 1,000 years, using image analysis and impact modeling, indicating rapid surface evolution and recent exposure events.

Contribution

It provides a new estimate of the space weathering timescale on Itokawa using bright mottles and impact flux comparison, linking surface features to recent seismic activity.

Findings

Space weathering timescale on Itokawa is approximately 10^3 years.

Surface exposure is due to recent seismic shaking from impacts.

Results align with space weathering by solar wind ions.

Abstract

Context. The space weathering timescale of near-Earth S-type asteroids has been investigated by several approaches (i.e., experiments, sample analyses, and theoretical approaches), yet there are orders of magnitude differences. Aims. We aim to examine the space weathering timescale on a near-Earth S-type asteroid, Itokawa using Hayabusa-AMICA images and further investigate the evolutional process of the asteroid. Methods. We focused on bright mottles on the boulder surfaces generated via impacts with interplanetary dust particles (IDPs). We compared the bright mottle size distribution with an IDP flux model to determine the space weathering timescale. Results. As a result, we found that the space weathering timescale on Itokawa's boulder surfaces is 10$^3$ years (in the range of 10$^2$-10$^4$ years), which is consistent with the timescale of space weathering by light ions from the solar wind. Conclusions. From this result, we conclude that Itokawa's surface has been weathered shortly in 10$^3$ years but portions of the surface are exposed via seismic shaking triggered by a recent impact that created the Kamoi crater.