Tiny crystals (pictured) found in Australia help scientists understand the ancient history of our planet's first magnetic field, which disappeared hundreds of millions of years ago. Examination of these crystals showed that this field was actually much more powerful than previously thought. This, in turn, can help to get an answer to the question about the causes of life on Earth.
These tiny, ancient crystals are encased in stones over half a billion years old, according to scientists' estimates. At that time, tiny magnetic particles floated in molten rocks. However, when the stones cooled down, these particles, oriented along the lines of the magnetic field, lost their mobility. This led to the fixation of the spatial orientation of magnetic particles, induced by the ancient magnetic field, and the preservation of information about its intensity to the present day. This field turned out to be much more powerful than was thought, according to a new study.
Modern science believes that the Earth's magnetic field is formed as a result of the rotation of a solid iron core inside a liquid shell, also composed of iron and called the outer core. This magnetic field protects the planet from harmful particles of the solar wind and cosmic rays.
The Earth's magnetic field is roughly 4.2 billion years old, according to this new study. However, up to 565 million years ago, long before the dinosaurs appeared, and on the eve of the famous "explosion" of the diversity of complex life forms at the beginning of the Cambrian period, the mechanism of the formation of this field was different from the modern one. At this time, the Earth did not have an inner core. However, magnesium oxide, dissolved in a completely liquid core, was slowly transferred from the core to the mantle as a result of the same giant collision that formed the Moon. This movement of magnesium caused the Earth to develop an early magnetic field.
When the reserves of magnesium oxide in the core came to an end, the associated magnetic field completely disappeared, but around this time a solid inner core had already formed - and it saved life on our planet.
Until now, scientists believed that the ancient magnetic field of the Earth, associated with the transition of magnesium from the core to the mantle, was much weaker than the modern magnetic field. However, the study of these tiny crystals of zircon, which formed during the period of dominance of the first magnetic field of the Earth, showed that this position was erroneous.
The study was published January 20 in the journal Proceedings of the National Academy of Sciences; lead author John Tarduno of the University of Rochester, USA.