Boulders on asteroid Toutatis as observed by Chang'e-2

TL;DR

This study uses Chang'e-2 images to analyze over 200 boulders on asteroid Toutatis, revealing a high degree of fragmentation and suggesting a rubble-pile structure with a surface age of about 1.6 billion years.

Contribution

It provides the first detailed boulder size distribution analysis of Toutatis, indicating its geological history and structural composition.

Findings

Boulder size distribution slope of -4.4 suggests high fragmentation.

Toutatis likely has a rubble-pile structure similar to Itokawa.

Surface crater retention age estimated at approximately 1.6 Gyr.

Abstract

Boulders are ubiquitously found on the surfaces of small rocky bodies in the inner solar system and their spatial and size distributions give insight into the geological evolution and collisional history of the parent bodies. Using images acquired by the Chang'e-2 spacecraft, more than 200 boulders have been identified over the imaged area of the near-Earth asteroid Toutatis. The cumulative boulder size frequency distribution (SFD) shows a steep slope of -4.4 $\pm$ 0.1, which is indicative of a high degree of fragmentation. Similar to Itokawa, Toutatis probably has a rubble-pile structure, as most boulders on its surface cannot solely be explained by impact cratering. The significantly steeper slope for Toutatis' boulder SFD compared to Itokawa may imply a different preservation state or diverse formation scenarios. In addition, the cumulative crater SFD has been used to estimate a surface crater retention age of approximately 1.6 $\pm$ 0.3 Gyr.