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January 21, 2020 07:00 am

New Research Provides Evidence of Strong Early Magnetic Field Around Earth

New research from the University of Rochester provides evidence that the magnetic field that first formed around Earth was even stronger than scientists previously believed. The research, published in the journal PNAS, will help scientists draw conclusions about the sustainability of Earth's magnetic shield and whether or not there are other planets in the solar system with the conditions necessary to harbor life. Phys.Org reports: Using new paleomagnetic, electron microscope, geochemical, and paleointensity data, the researchers dated and analyzed zircon crystals -- the oldest known terrestrial materials -- collected from sites in Australia. The zircons, which are about two-tenths of a millimeter, contain even smaller magnetic particles that lock in the magnetization of the earth at the time the zircons were formed. Previous research by [John Tarduno, Professor of Earth and Environmental Sciences and Dean of Research for Arts, Sciences, and Engineering at Rochester] found that Earth's magnetic field is at least 4.2 billion years old and has existed for nearly as long as the planet. Earth's inner core, on the other hand, is a relatively recent addition: it formed only about 565 million years ago, according to research published by Tarduno and his colleagues earlier this year. While the researchers initially believed Earth's early magnetic field had a weak intensity, the new zircon data suggests a stronger field. But, because the inner core had not yet formed, the strong field that originally developed 4 billion years ago must have been powered by a different mechanism. "We think that mechanism is chemical precipitation of magnesium oxide within Earth," Tarduno says. The magnesium oxide was likely dissolved by extreme heat related to the giant impact that formed Earth's moon. As the inside of Earth cooled, magnesium oxide could precipitate out, driving convection and the geodynamo. The researchers believe inner Earth eventually exhausted the magnesium oxide source to the point that the magnetic field almost completely collapsed 565 million years ago. But the formation of the inner core provided a new source to power the geodynamo and the planetary magnetic shield Earth has today.

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