- Gravity causes dense material (e.g. iron) to separate from
lighter material (e.g. rock) of a liquid planet.
- The dense material sinks toward the center.
The lighter material floats to the top.
- Shortly after they formed, most planets
due to radioactive heating and the heat from impacts.
- Iron and rock are two of the most abundant
substances in the inner solar system.
- Terrestrial planets have iron cores and rocky surfaces.
Created May 2, 1996