4.4 Formation of the Solar System

Why Are the Planets so Diverse?

If the planets all formed in the same process, why are they all so different from each other?

As it turns out, the position of each planet in the nebula determined many of its characteristics. This has a lot to do with the temperature in various parts of the nebula.

Near the centre, where the Sun formed, the temperatures were very high. This means that ices were vapourized, and light atoms such as hydrogen and helium were kept from condensing. In this area, particles of rock and metal gathered to form small, rocky planets. These planets are known as the “terrestrial planets:”

- Mercury,
- Venus,
- Earth, and
- Mars.

Further out from the Sun, ices survived and joined with other particles to form the cores of planets. At these colder temperatures, hydrogen, helium, and other gases were able to condense. Particles, too, were sucked into these giant planets known as the “Jovian planets.” These giants are:

- Jupiter,
- Saturn,
- Uranus, and
- Neptune.