Interpretation of (596) Scheila's Triple Dust Tails

Strange-looking dust cloud around asteroid (596) Scheila was discovered on 2010 December 11.44-11.47. Unlike normal cometary tails, it consisted of three tails and faded within two months. We constructed a model to reproduce the morphology of the dust cloud based on the laboratory measurement of high-velocity impacts and the dust dynamics. As a result, we succeeded in reproducing the peculiar dust cloud by an impact-driven ejecta plume consisting of an impact cone and downrange plume. Assuming an impact angle of 45°, our model suggests that a decameter-sized asteroid collided with (596) Scheila from the direction of (α_im, δ_im) = (60°, -40°) in J2000 coordinates on 2010 December 3. The maximum ejection velocity of the dust particles exceeded 100 m s^-1. Our results suggest that the surface of (596) Scheila consists of materials with low tensile strength.