I am going to use a simple principles of chemistry to disprove why the earth can not have an iron core. It more than likely contains an solid oxygen core. .

What an solid iron (nickel) core implies is that somehow iron is able to hold more electrons than is natural within chemistry, inspite of all the highly electronegative oxygen present in the mantle. This would imply that an iron core should be highly reduced (has a lot of extra electrons that oxygen would like to have).

The surface of the earth is an oxidizing environment. This implies that a strong electro-chemical potential would exist between the core and the surface. This means the core should be oxidized by the surface potential, i.e, rusting away, and/or its potential to surface should be reducing the surface. If we had oceans of oil, an iron core would make sense, but with water and an oxygen atmosphere on the surface the surface is showing no signs of being reduced by a huge core that is maybe 1000 times larger. The sun creates a surface reduction potential (photosynthesis into C-H ), but even this is oxidized by metabolism and fire.

What makes more sense is an solid oxygen core. The high electronegativity of oxygen would allow it to hold a extra negative charge in a stable way, i.e, anion, without generating much or any reduction potential on the surface. If we add a light extra sprinkle of electron density, a stable potential could exist between the core and surface. The petroleum deposits suggest a least a small reduction potential between the core and surface at one time. The modern magnetic field suggests that a dipole potential still exists to some extent. The slight negative charge within the oceans also suggests a slight reduction potential stemming from the core. Not a huge reduction potential that iron core should be able to generate. Hydrogen sulfide from the mantle is also due to a slight reduction potential within the mantle.

Thank you for your insight.

Hi MDT and BrianKP,

You have an interesting theory there. What I would like to add is that there is a lot of evidence for an iron core. I will give a couple of dot points here...
* The earths magnetism could not be explained by an "oxygen" core. The center of the earth is the equivalent of a self-exciting homo-polar generator made of strongly magnetic material.
* There are many meteorites that appear to have come from the core of other worlds. They are composed of Nickel Iron. Remember all that Nickel Iron has come from Supernovas of distant stars and a lot of this debris are the result of these titanic processes.
* The propagation of sound through the body of the Earth (massive earthquakes) matches the model of the Nickel Iron Core.
* Inspection of phase diagrams of nickel iron mixtures with an olivine outer core at those high interior temperatures and pressures support chemistry models of the core being Nickel Iron.

It is possible that other materials might be the reason for this special phenomenon of the Earth's Magnetism but I would not hold out too much hope. Iron is probably the answer. A ready supply of Iron is found among the "loose change" lying around in our Solar System... this still supports this view... since the planet's themselves condensed from large collections of these particles that were in huge numbers previously about 5 Billion Years ago but are now currently more rare in our area of space. Still, the majority of them are Nickel Iron like our core. The Earth's early atmosphere had no free oxygen and it is unlikely that too much oxygen has "oozed" into the region of the core due to it's low density and the high temperatures and pressures there produced by substantially denser material.

Cheers

How about a uranium core operating as a fission reactor producing extra
heat to keep the earth warmer than otherwise from its formation more
than 4 billion years ago?

How about a solid iron core that came along and knocked the Moon out of the centre of the Earth while our planet was still forming. See NASA photo of Moons' St Pierre-Aitken crater.

And another thing. How about that core (which would have been spinning madly) turning the Earth into one BIG hydrogen fuel cell and creating water as a by product while using up all Earths pure hydrogen and oxygen! Hydrogen is the most abundant element in the universe and Earth now has none naturally occuring. The oxygen was gradually replaced by plants etc. as we all know.