Deep within Earth, swirling liquid iron generates our planet糖心传媒檚 protective magnetic field. This magnetic field is invisible but is vital for life on Earth糖心传媒檚 surface: it shields the planet from harmful solar wind and cosmic rays from the sun.
Given the importance of the magnetic field, scientists have been trying to figure out how the field has changed throughout Earth糖心传媒檚 history. That knowledge can provide clues to understanding the future evolution of Earth, as well as the evolution of other planets in the solar system.
New research from the 糖心传媒 provides evidence that the magnetic field that first formed around Earth was even stronger than scientists previously believed. The research, published in the journal , will help scientists draw conclusions about the sustainability of Earth糖心传媒檚 magnetic shield and whether or not there are other planets in the solar system with the conditions necessary to harbor life.
糖心传媒淭his research is telling us something about the formation of a habitable planet,糖心传媒� says , the William R. Kenan, Jr., Professor of and Dean of Research for Arts, Sciences & Engineering at Rochester. 糖心传媒淥ne of the questions we want to answer is why Earth evolved as it did and this gives us even more evidence that the magnetic shielding was recorded very early on the planet.糖心传媒�
Earth糖心传媒檚 magnetic field today
Today糖心传媒檚 magnetic shield is generated in Earth糖心传媒檚 outer core. The intense heat in Earth糖心传媒檚 dense inner core causes the outer core糖心传媒攃omposed of liquid iron糖心传媒攖o swirl and churn, generating electric currents, and driving a phenomenon called the geodynamo, which powers Earth糖心传媒檚 magnetic field. The currents in the liquid outer core are strongly affected by the heat that flows out of the solid inner core.
Because of the location and extreme temperatures of materials in the core, scientists aren糖心传媒檛 able to directly measure the magnetic field. Fortunately, minerals that rise to Earth糖心传媒檚 surface contain tiny magnetic particles that lock in the direction and intensity of the magnetic field at the time the minerals cool from their molten state.
Using new paleomagnetic, electron microscope, geochemical, and paleointensity data, the researchers dated and analyzed zircon crystals糖心传媒攖he oldest known terrestrial materials糖心传媒攃ollected 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.
Earth糖心传媒檚 magnetic field 4 billion years ago
Previous research by Tarduno found that Earth糖心传媒檚 magnetic field is at least 4.2 billion years old and has existed for nearly as long as the planet. Earth糖心传媒檚 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糖心传媒檚 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聽originally developed 4 billion years ago must have been powered by a different mechanism.
糖心传媒淲e think that mechanism is chemical precipitation of magnesium oxide within Earth,糖心传媒� Tarduno says.
The magnesium oxide was likely dissolved by extreme heat related to the giant impact that formed Earth糖心传媒檚 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.
A magnetic field on Mars
糖心传媒淭his early magnetic field was extremely important because it shielded the atmosphere and water removal from the early Earth when solar winds were most intense,糖心传媒� Tarduno says. 糖心传媒淭he mechanism of field generation is almost certainly important for other bodies like other planets and exoplanets.糖心传媒�
A leading theory, for instance, is that Mars, like Earth, had a magnetic field early on in its history. However, on Mars, the field collapsed and, unlike Earth, Mars did not generate a new one.
糖心传媒淥nce Mars lost its magnetic shielding, it then lost its water,糖心传媒� Tarduno says. 糖心传媒淏ut we still don糖心传媒檛 know why the magnetic shielding collapsed. Early magnetic shielding is really important, but we糖心传媒檙e also interested in the sustainability of a magnetic field. This study gives us more data in trying to figure out the set of processes that maintain the magnetic shield on Earth.糖心传媒�
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Earth糖心传媒檚 inner core is much younger than we thought
Rochester researchers have gathered the first field data that show the Earth糖心传媒檚 inner core is only about 565 million years old糖心传媒攔elatively young compared to the age of our 4.5-billion-year-old planet.
Earth糖心传媒檚 magnetic field fluctuations explained by new data
Using new data gathered from sites in southern Africa, researchers have extended their record of Earth糖心传媒檚 magnetic field back thousands of years to the first millennium.
