Density and Planetary Differentiation

• 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.

Density of Earth in g/cm^3

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.

Elements Settled

• While Earth was hot, elements began to settle by density.

• Denser elements sank and less dense elements floated.

• 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.

• 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.

Layers vs No Layers

• Scientists can infer that a planet with out layers must have been cooler than Earth when formed.

Which moon(s) of Jupiter formed molten?