  Deflection of stray asteroids by low-momentum impacts is an Earth's key
defense strategy. Using a proof-of-principle numerical model, we show that even
such impacts on rubble pile asteroids (RPAs) may lead to fragmentation because
of inherent internal stress chains. Such chains occur in three- and
two-dimensional (2D) aggregates and we study this phenomenon in 2D. We first
establish the existence of stress chains in our aggregates and then show that
the dynamic shear stress and displacements are highest along the chains,
increasing significantly the risk of fracturing there. Our simulations suggest
that this phenomenon is independent of the aggregate's particle size
distribution. We conclude that future studies are needed to quantitatively
assess fragmentation risk as a function of stress chain statistics in RPAs.
