it is known that giant planets can open cavities in the inner part of the disk (Rice et al., 2003; Varniere et al., 2006; Crida and Morbidelli, 2007). If this happened in this case, Jupiter and Saturn could not migrate outward. Thus, we think that it is important to re-simulate the dynamics of Jupiter and Saturn using our new, trustable algorithm.

-   the evolution of Jupiter presented in MS01 is probably inconsistent with the solar system architecture. In fact, after Jupiter and Saturn lock in their mutual 2:3 resonance, their outward migration is rather fast. Jupiter increases its orbital radius by $\sim 40$% in 1,000 orbits. If this really occurred in the Solar System, Jupiter would have been at some time in the middle of the asteroid belt. The properties of the asteroid belt (in particular the quite tight zoning of the taxonomic types) exclude this possibility. Thus, we need to find orbital evolutions that are much more stationary than the one presented in MS01.

-   MS01 claim that the trapping of Jupiter and Saturn into the 2:3 resonance is the most likely outcome of their evolution in the gas disk. This might be problematic in the context of the 