Comparison between the planets in the solar
system.
The Planets:
When we look at the solar system it is apparent that planets fall into
two distinct groups, controlled by where they developed in relation to
the sun: a) the small dense inner planets and b)the large gas giants. This
is quite apparent when we compare the characteristics of the two sets of
planets.
Inner Planets
|
Outer Planets
|
Solid |
Gaseous |
Craters |
No Craters |
Denser |
Less Dense |
Massive molecule atmosphere (relatively) |
H, He atmosphere |
Small |
Large |
Nearly spherical |
Oblate |
Rapid Revolution |
Slower Revolution |
Slower Rotation |
Rapid Rotation |
No rings |
Rings |
Few moons (satellites) |
Many moons |
The outer planets
Still resembling the original planets in many ways, the giant, massive,
outer planets condensed in an area of the solar system were temperatures
were low and allowed Hydrogen, Helium and other light materials to accumulate.
Based on data received from the Voyager probes and calculations, we know
they share common characteristics.
They all contain dense, rocky cores surrounded by a liquid layer of
either hydrogen or water and are enveloped in thick atmospheres of Hydrogen
and Helium, (and methane also, in the case of Uranus and Neptune). Compared
to the inner planets, they are rapidly rotating giants, with rings and
are accompanied by many moons. Their composition (along with that of the
sun) gives us insight in what the original nebular material must have been
like.
The inner planets
Like the outer planets, the inner planets represent variations on a basic
theme. Depleted in light materials because of higher nebular temperatures,
they are richer in heavier elements, dense, rocky, slowly rotating, small
and warm, and have few moons. Depending on the intensity of their gravitational
field they may have atmospheres. Except for Mercury and the Moon, they
have geologically active surfaces.
The remainder of the objects in the Solar System are smaller than the
planets and are covered on the next page. |