1. Density and Planetary Differentiation

2. Planetary Differentiation is the separating of a planet into different layers due to differences in density.
Seismic waves tell scientists Earth has four layers of different densities because of their speed.

3. Density of Earth in g/cm^3

4. Early Earth Scientists infer Earth was formed 4.6 billion years ago.
When Earth first formed, it was extremely hot!
The entire planet was a ball of molten elements held together by gravity.

6. Elements Settled
While Earth was hot, elements began to settle by density.
Denser elements sank and less dense elements floated.

8. Iron, Nickel, and several other heavy elements (metals) sank to form the inner and outer cores.
Elements such as Magnesium and Iron silicates (denser rocks) settled in the middle forming the mantle.

10. Lighter elements such as Sodium and Potassium Silicates (less dense rocks) settled on the surface forming the crust.
Liquids (water) formed the oceans above the crust and gasses formed the atmosphere.

12. Layers vs No Layers
Scientists can infer that a planet with out layers must have been cooler than Earth when formed.

13. Which moon(s) of Jupiter formed molten?