Size and composition are the two major characteristics shared by Jupiter, Saturn, Uranus, and Neptune.
The smallest outer planet, with the exception of Pluto, which is in a category by itself, is Neptune, and Neptune is almost four times larger than Earth.
The outer planets have small cores and huge gaseous outer surfaces.
When the Sun developed into a main sequence star, the lightest elements, gases, that were expelled into space traveled the farthest, and they soon became planets.
The heavier elements were incorporated into the inner, or terrestrial planets.
The outer planets also all have many satellites orbiting them, from Neptune’s eight moons to more than twenty orbiting Saturn.
The gas giants, Jupiter, Saturn, Uranus, and Neptune, have small, rocky cores, semisolid mantles, and large outer layers of gases.
While Saturn is best known as the ringed planet, all gas giants have ring systems.
If the theory of the big bang was slightly correct which we don’t know, then the mass or content of each of the planets would deem to be from the same source, the gases which surround the rest do we know for sure that hydrogen & oxygen make liquid as we know as water, for the earth to this day still have eruptions surely this indicates that earth is relative young, not like the moon being cold and without gases, Can the gases be classified and if so what do the match on our planet ,the whole system did it start or was formed form 1 single or several collisions, how has the earth got everything in harmony and why each day do we discover newer forms of materials and plant life its like everything adapts to every day change no matter what,very interesting and the theorys have still a long way to go,