  Using numerical simulations, we show that smooth migration of the giant
planets through a planetesimal disk leads to an orbital architecture that is
inconsistent with the current one: the resulting eccentricities and
inclinations of their orbits are too small. The crossing of mutual mean motion
resonances by the planets would excite their orbital eccentricities but not
their orbital inclinations. Moreover, the amplitudes of the eigenmodes
characterising the current secular evolution of the eccentricities of Jupiter
and Saturn would not be reproduced correctly; only one eigenmode is excited by
resonance-crossing. We show that, at the very least, encounters between Saturn
and one of the ice giants (Uranus or Neptune) need to have occurred, in order
to reproduce the current secular properties of the giant planets, in particular
the amplitude of the two strongest eigenmodes in the eccentricities of Jupiter
and Saturn.
