The iron catastrophe was a major event early in the history of Earth. After accretion 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.
This large spinning mass of super-hot metal is responsible for the magnetosphere, which protects the Earth from solar wind and the most harmful components of solar radiation coming from our Sun. The magnetosphere protects both Earth's atmosphere and life to the present day and distinguishes the planet from its close celestial neighbour, Mars, which no longer has a significant magnetic field nor comparable atmosphere. Contrary to the implication of a catastrophe, this event was necessary for life to emerge and evolve on Earth for, without it, the atmosphere would have also been stripped from the Earth long before the present epoch.
Another theory, however, suggests Mars did once experience its own iron catastrophe and was once shielded by a magnetosphere. By this theory Mars has simply cooled faster than the Earth and has solidified its spinning iron center into sync with its continental crust, gradually shutting down its magnetosphere. The finding of signs of liquid water once existing on Mars suggests that it once had its own magnetic shield to keep the water in the atmosphere of the planet from being blown into space by solar wind.
- Charles Frankel, 1996, Volcanoes of the Solar System, Cambridge University Press, p. 7–8, ISBN 0-521-47770-0
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