Five hundred and sixty-five million years ago, Earth's magnetic field almost disappeared.

But a geological phenomenon might have saved it, a new study suggests. Earth's then-liquid core likely began to solidify around that time, which strengthened the field, the group reported yesterday (Jan. 28) in the journal Nature Geoscience. This is important because the magnetic field protects our planet and its inhabitants from harmful radiation and solar winds — streams of plasma particles thrown our way by the sun.

Scientists figured out what our planet's core was like back then by looking at crystals the size of grains of sand.

They picked up samples of plagioclase and clinopyroxene — minerals that were formed 565 million years ago — in what is now eastern Quebec, Canada. These samples contain tiny magnetic needles about 50 to 100 nanometers in size, which, in molten rock, orient themselves in the direction of the magnetic field at the time.


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