Why Does Earth Have an Iron Core?

[Chemist@]

Why is Earth's nucleus mostly made from iron?

 

[snorkack]

Why is Earth's nucleus mostly made from iron?

1) Iron is the most common siderophile
2) Earth does not contain enough oxygen to bind to all iron. While a lot of iron is bound to oxygen and found in rocks, some of it concentrated in iron ores and some scattered, much iron is left over as metal.
3) Iron with siderophile alloying elements is denser than rocks and sinks to centre. Everything else is either siderophile and mixed with iron, or lithophile which mixes with less dense rocks and floats in top of iron.

 

[mikeph]

http://en.wikipedia.org/wiki/Iron_catastrophe

The iron catastrophe was a major event early in the history of Earth. After accumulation of the Earth's material into a spherical mass, the material was mostly uniform in composition. While residual heat from the collision of the material that formed the Earth was significant, heating from radioactive materials in this mass further increased the temperature until a critical condition was reached, when the material was molten enough to allow movement. At this point, the denser iron and nickel, evenly distributed throughout the mass, sank to the centre of the planet to form the core - an important process of planetary differentiation. The gravitational potential energy released by the sinking of the dense NiFe globules increased the temperature of the protoplanet above the melting point resulting in a global silicate magma which accelerated the process. This event occurred at about 500 million years into the formation of the planet.

 

[mikelepore]

We have a second generation solar system, which means that much of the material came from the death of a previously-existing star. As stars gradually reach the end of their life, their chemical composition changes in the direction of the element that has the lowest amount of nuclear potential energy, which is iron. Iron is to nuclear reactions what ash is to combustion, an end product out of which no more energy can be extracted.

 

[Chemist@]

The catastrophe looks like Archimedes' law. Thanks for every answers. It is nice to understand nature as much as it is possible.