Structure-dependent fragmentation risk of rubble-pile asteroids on low-impacts

A key strategy in defending against stray asteroids is deflection from a collision trajectory by a low-momentum impact. This is to avoid a potential rain of large hazardous fragments, which high-momentum blasts may generate. Using a proof-of-principle numerical model, we show that even low-momentum impacts on rubble pile asteroids (RPAs), which most asteroids are, may lead to their fracturing into large fragments because of their internal non-uniform chain-like stress distribution. Since stress chains occur in three- and two-dimensional (2D) loose aggregates, we study low-momentum impacts on gravity-aggregated clusters in 2D. We establish that stresses are indeed supported by chains and show that the post-impact dynamic shear stress and displacement rates are highest along the chains, increasing significantly the risk of fracturing there. Our simulations suggest that this phenomenon is independent of the cluster's particle size distribution. We conclude that future studies must be carried out to quantify the relations between the risk of fracturing and stress chain statistics in RPAs.