There is a clear distinction between the
Terrestrials, Jovians, and Icy planets
(also, as not apparent from the Table, however, another distinction is that
all of the Jovian planets have extensive satellite and
ring systems). We note that there is also a dichotomy in the
properties of the Jovian planets, Jupiter/Saturn and Uranus/Neptune. The
cause of the differences between
Jupiter/Saturn and Uranus/Neptune is probably due to the timing problem we
discussed earlier when we talked about the formation of the Solar System. The
reason Jupiter and Saturn are so massive and large is due to the fact that they
formed where water ice could exist and thus they were able to grow to large
masses rather quickly. Their large masses enabled them to capture the abundant
hydrogen and helium gas which explains their composition and their overly large
masses. Uranus and Neptune forming slightly farther out in the Solar Nebula,
also formed where water ice existed but everything happened more slowly. Before
they reached the point where they could capture significant amounts of hydrogen
and helium gas, the young Sun ignited became bright, and generated an
intense Solar Wind and cleared the gas out of the Solar Nebula. This
halted the formation process of Uranus and Neptune not allowing them to reach
their full glories.
