The spherical Brazil Nut Effect and its significance to asteroids

Abstract

Many asteroids are likely rubble-piles that are a collection of smaller objects held together by gravity and possibly cohesion. These asteroids are seismically shaken by impacts, which leads to excitation of their constituent particles. As a result it has been suggested that their surfaces and sub-surface interiors may be governed by a size sorting mechanism known as the Brazil Nut Effect. We study the behavior of a model asteroid that is a spherical, self-gravitating aggregate with a binary size-distribution of particles under the action of applied seismic shaking. We find that above a seismic threshold, larger particles rise to the surface when friction is present, in agreement with previous studies that focussed on cylindrical and rectangular box configurations. Unlike previous works we also find that size sorting takes place even with zero friction, though the presence of friction does aid the sorting process above the seismic threshold. Additionally we find that while strong size sorting can take place near the surface, the innermost regions remain unsorted under even the most vigorous shaking.

References in corpus (9)

• Density of asteroids
• The Strength of Regolith and Rubble Pile Asteroids
• Numerical simulations of granular dynamics. I. Hard-sphere discrete element method and tests
• The Brazil-nut effect and its application to asteroids
• Asteroid Models from Multiple Data Sources
• Granular convection and the Brazil nut effect in reduced gravity
• Numerical Simulations of Collisional Disruption of Rotating Gravitational Aggregates: Dependence on Material Properties
• Micro-meteoroid seismic uplift and regolith concentration on kilometric scale asteroids
• On the rotation rates and axis ratios of the smallest known near-Earth asteroids---the archetypes of the Asteroid Redirect Mission targets

Cited by in corpus (7)

• Creep stability of the proposed AIDA mission target 65803 Didymos: I. Discrete cohesionless granular physics model
• Small Solar System Bodies as granular media
• Impact Excitation of a Seismic Pulse and Vibrational Normal Modes on Asteroid Bennu and Associated Slumping of Regolith
• Q-type asteroids: Possibility of non-fresh weathered surfaces
• The fast spin of near-Earth asteroid (455213) 2001 OE84, revisited after 14 years: constraints on internal structure
• Propagation and attenuation of pulses driven by low velocity normal impacts in granular media
• Boulder Stranding in Ejecta Launched by an Impact Generated Seismic Pulse