How did Earth’s inner core freeze solid?
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A high concentration of carbon within Earth’s inner core could explain a long-standing mystery about how the deepest part of our planet froze solid – a process that kick-started the magnetic field protecting life on the surface.
Earth’s inner core presents a paradox for geophysicists: it first formed as a massive liquid ball of mostly iron, then began to solidify within the last billion years. In order for that freezing process to start in a pure iron object, it would have had to cool by at least 700 kelvin in…