How small pebbles and dust strengthen small asteroids

What is it about?

In a micro-gravity environment, cohesive and adhesive forces between the pebbles and dust that form an asteroid become comparable in magnitude to the weight of these particles. In this paper, we analyze the contribution of these small forces (the same that make dust stick to everything else) to the strength of an asteroid. Notice that these forces are always there, it is gravity that is reduced and so the effects of cohesion and adhesion are visible. We find that the smaller the size of the grains, the greater the tensile strength of the granular system (the asteroid). Which would imply that the small pebbles and dust form a sort of Van der Waals cement that keeps the larger boulders and rocks in place.

Featured Image

Why is it important?

This helps us understand the existence of asteroids that are not monolithic and still rotate faster than the ~2.3h rotation period limit that has been observed for larger asteroids. This limit is easily explained for larger asteroids, where cohesion is not as important, as a gravitational spin limit. For exploration and planetary defense missions, this provides some insight into the strength of asteroids and how to deal with them if we have to at some point in the future. Landing, sampling and penetrometry operations need this kind of information.

Perspectives