Evolution of a simulation with low-mass giant planets. 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 at 25 microns as a function of time. The rough observational limit of the MIPS instrument on NASA’s Spitzer Space Telescope 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/scatter_lowmass_54.mpg.