  Although the long-term numerical integrations of planetary orbits indicate
that our planetary system is dynamically stable at least +/- Gyr, the dynamics
of our Solar System includes both chaotic and stable motions: the large planets
exhibit remarkable stability on gigayear timescales, while the subsystem of the
terrestrial planets is weekly chaotic with a maximum Lyapunov exponent reaching
the value of 1/5 Myr. In this paper the dynamics of the
Sun--Venus--Earth--Mars-Jupiter--Saturn model is studied, where the mass of
Earth was magnified via a mass factor $\kappa_E$. The resulting systems
dominated by a massive Earth may serve also as models for exoplanetary systems
that are similar to our one. This work is a continuation of our previous study,
where the same model was used and the masses of the inner planets were
uniformly magnified. That model was found to be substantially stable against
the mass growth. Our simulations were undertaken for more then 100 different
values of K for a time of 20, in some cases for 100 Myrs. A major result was
the appearance of an instability window at K = 5, where Mars escaped. This new
result has important implications for the theories of the planetary system
formation process and mechanism. It is shown that with increasing K the system
splits into two, well separated subsystems: one consists of the inner, the
other one consists of the outer planets. According to the results the model
became more stable as K increases and only when K >= 540 Mars escaped, on a Myr
timescale. We found an interesting protection mechanism for Venus. These
results give insights also to the stability of the habitable zone of
exoplanetary systems, which harbour planets with relatively small
eccentricities and inclinations.
