Simulating regoliths in microgravity

TL;DR

This paper investigates the behavior of granular materials, or regolith, in microgravity environments, revealing transient weakening effects and implications for surface stability on small celestial bodies.

Contribution

It provides the first measurements of transient weakening of granular material after shear reversal in microgravity, highlighting potential differences in surface stability of small bodies.

Findings

Granular force networks may be weaker in microgravity.

Surface stability of small bodies could be more fragile.

Impact and landing effects vary with impact angle and history.

Abstract

Despite their very low surface gravities, the surfaces of asteroids and comets are covered by granular materials - regolith - that can range from a fine dust to a gravel-like structure of varying depths. Understanding the dynamics of granular materials is, therefore, vital for the interpretation of the surface geology of these small bodies and is also critical for the design and/or operations of any device planned to interact with their surfaces. We present the first measurements of transient weakening of granular material after shear reversal in microgravity as well as a summary of experimental results recently published in other journals, which may have important implications for small-body surfaces. Our results suggest that the force contact network within a granular material may be weaker in microgravity, although the influence of any change in the contact network is felt by the granular material over much larger distances. This could mean that small body surfaces are even more unstable than previously imagined. However, our results also indicate that the consequences of, e.g., a meteorite impact or a spacecraft landing, may be very different depending on the impact angle and location, and depending on the prior history of the small body surface.