Earth’s magnetic field or earlier than expected

Researchers have found more evidence that our planet had a strong magnetic field 4.2 billion years ago, 350 million years after Earth formed, 750 million years earlier than previously thought, Science reported. Magnetic fields will shield the Earth, protecting the atmosphere from the sun’s high-energy particles, and helping life to gain a foothold.

Earth’s magnetic field, which formed earlier than expected, was 4.2 billion years ago, helping to protect the planet’s atmosphere

Earth's magnetic field or earlier than expected

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With little remaining rock to study, geologists have struggled to reconstruct the Earth’s ancient period, which was seen 4.55 billion to 4 billion years ago. But scientists can find fragmented but controversial clues from the young rocks of Mount Jack 3 billion years ago in western Australia. The rocks contain tiny crystals of a hard mineral called zircon, which fell off from the older block, the ancient formation of the ancient zeazhou rock formed 4.2 billion years ago by cooling magma.

An international team of researchers led by geophysicist John Tarduno of the University of Rochester in New York said the crystals also preserved evidence of the ancient Earth’s magnetic field. But not all researchers believe the results, as it pushed the recognized Earth’s magnetic field “birthday” forward by 750 million years. “There are a lot of research groups trying to prove our findings wrong,” Tarduno said. “

Tarduno and colleagues first reported the findings in Science in 2015. There are about 24 zircons in the rock, tiny particles of magnetite, an iron-containing mineral that effectively turns each crystal into a miniature strip magnet. The researchers found that the magnetic fields contained in these particles were consistent, and only when the magnetite cooled and was exposed to the magnetic field.

Tarduno’s team says the magnetization was a mark from 4.2 billion years ago, when the original rock containing zircon cooled for the first time. At any given moment, however, if magnetite particles become hot enough – more than about 600 degrees Celsius – they lose their magneto-arrangement and regain the new magnetization when they cool down again.

Benjamin Weiss, a geologist at the Massachusetts Institute of Technology, questioned Tarduno’s claim that “a heating event like this may have occurred 2.6 billion years ago.” He said, “These zircons have an incredibly long and unknown history. “

In a recent issue of the Proceedings of the National Academy of Sciences, Tarduno’s team collected a new set of evidence that magnetization occurred in ancient times rather than long after. There are areas rich in lithium-ion in zircon crystals that, when heated, seep into adjacent areas over time through a process known as chemical diffusion. Tarduno and colleagues measured the concentration of lithium at these regional boundaries in three zircon crystals. In both crystals, they found limited evidence of diffusion. This suggests that they have never been heated above 600 degrees Celsius in their 4.2 billion-year history — their magnetic properties are primitive, Tarduno said. “I think it’s a remarkable discovery. “

What’s more, on the other hand, the zircon crystal, which shows signs of heating, is an exception: it retains an unusually weak magnetic signal. In 2015, Tarduno and colleagues concluded that this may be evidence of strange changes in magnetic fields 4.2 billion years ago. But now he thinks the particular zircon appears to have been magnetic later, and the faint signal it retains is negligible when discussing the Earth’s earliest magnetic fields. Tarduno says this suggests that in ancient times, the Earth actually had a magnetic field, with a geomagnetic generator at its core that was as powerful as it is today.

Mark Harrison, a geologist at the University of California, Los Angeles, is not convinced by the new study. Because lithium ions penetrate the boundary, it takes high temperatures and a long time. If the heating causes the zircon to exceed 600 degrees Celsius, it will be enough to reset the magnetism of the zircon and non-proliferation of lithium, even though it has only been preserved for 10,000 years (for geologists, it is a flash). “I don’t think it’s conclusive evidence. He said.

Claire Nichols, a geologist at the Massachusetts Institute of Technology who was not involved in any of the Jack’s studies, said that by analyzing the rocks of Greenland, the Earth’s magnetic field existed at least 3.7 billion years ago. “It’s good that different research teams are pushing each other to use more and more advanced technology. “This gives us the best chance to understand the earliest records of geomagnetic generators, ” she said. “