Granular processes on Itokawa, a small near-Earth asteroid: implications for resource utilization

Crucial questions for possible utilization of Near Earth Asteroids include how to break asteroid materials down to particle sizes that can be processed. This remained difficult to answer because of the limited number and resolutions of images previous obtained through asteroid missions. Recently, the Hayabusa spacecraft obtained unprecedentedly high-resolution images of a ~300m-sized asteroid, Itokawa, which gives unique opportunity to discuss the nature of surface materials on a small asteroid. Hayabusa reveals that the asteroid is covered by fine- and coarse-grained materials, including granules, pebbles, cobbles, and boulders up to tens of meters. Gravels on this small asteroid appear to be loosely deposited along the gravitational equipotential surfaces. The existence of smooth areas as well as boulder-rich rough areas indicate that gravels should have experienced migrations and segregations. Thus, the issue regarding the breaking of asteroid materials appears to have been resolved naturally, at least for this asteroid, which has important implications for future robotic missions dedicated to resource exploration and utilization.