A new method for identifying dynamical transitions in rubble-pile asteroid scenarios

Context. Evidence supports the idea that asteroids are rubble piles, that is, gravitational aggregates of loosely consolidated material.This makes their dynamics subject not only to the complex N-body gravitational interactions between its constituents, but also to the laws of granular mechanics, which is one of the main unsolved problems in physics.Aims. We aim to develop a new method to identify dynamical transitions and predict qualitative behavior in the granular N-bodyproblem, in which the dynamics of individual bodies are driven both by mutual gravity, contact and collision interactions.Methods. The method has its foundation in the combination of two elements: a granular N-body simulation code that can resolve thedynamics of granular fragments to particle-scale precision, and a theoretical framework that can decode the nature of particle-scaledynamics and their transitions by means of ad hoc indicators.Results. We present here a proof-of-concept of the method, with application to the spinning rubble-pile asteroid problem. We investigate the density-spin parameter space and demonstrate that the approach can identify the breakup limit and reshape region forspinning rubble-pile aggregates.Conclusions. We provide the performance of several ad hoc indicators and discuss whether they are suitable for identifying andpredicting the features of the dynamical problem.