Evolution of a reference mixed simulation in which the giant planets underwent a violent instability after 42.8 Myr of evolution. The initial giant planet masses were, in order of increasing orbital distance, 0.96, 0.46 and 0.64   M_J. Left: orbital eccentricity vs. semimajor axis of each body in the simulation. The size scales with the mass^1/3 and the color corresponds to the water content, using initial values taken to solar system data (Raymond et al. 2004) and re-calculated during impacts by mass balance. The giant planets are shown as the large black bodies and are not on the same size scale. Top right: the spectral energy distribution of the dust during five simulation snapshots, as observed from a distance of 10 pc. The dashed line represents the stellar photosphere. Bottom right: the ratio of the dust-to-stellar flux F/F_star at 25   μm as a function of time. The rough Spitzer observational limit is shown with the dashed line (Trilling et al. 2008). A movie of this simulation is available online or at http://www.obs.u-bordeaux1.fr/e3arths/raymond/scatterSED_199.mpg.