(Photo: Wikimedia Commons/NASA, ESA and A. Schaller)
The magnetic field observed on Earth billions of years ago and today has similarities, according to a new study.
Earth's Magnetic Field Remains The Same?
A team of researchers at the University of Oxford, UK, and the Massachusetts Institute of Technology in the US suggests that ancient species preserved in the oldest fossils on Earth may have experienced a planetary magnetic field similar to our own.
Team leader Claire Nichols of Oxford's Department of Earth Sciences found the results interesting because the Sun was generating intense solar wind. The study suggested that the planet had the same strength of magnetic field 3.7 billion years ago. The same intense magnetic field would have offered less shielding for emerging life at the time because the magnetosphere, which provides a protective bubble around Earth, was much smaller.
As the magnetosphere shields us from solar wind and cosmic radiation, many scientists believe that life as we know it would not have been conceivable without it. However, the exact date and strength of its appearance remained unknown to experts until recently.
The team examined rocks from southwest Greenland's northernmost point on the Isua Supracrustal Belt for the new study. Heat-induced magnetite crystals developed in these rocks billions of years ago, and iron oxide particles inside stored the direction and strength of the surrounding magnetic field.
The researchers found that just three major heat episodes occurred throughout the history of this stretch of land. The first and hottest one, which occurred 3.7 billion years ago, reached 550 °C and heated the bedrock. The Earth's magnetic field is preserved in the 3.7 billion-year-old record because the two subsequent heating events were not as strong and did not raise the temperature of the rocks above 400 °C. This is because the first event is locked in the magnetic field.
The findings imply that the process that creates the magnetic field on Earth today was just as effective as the planet's primordial magnetic dynamo. This discovery could provide insight into plate tectonics and mantle convection by enabling scientists to determine when the Earth's solid core first formed.
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Is Magnetic Field Key Criteria For Habitability?
The prospect of extraterrestrial life is the most significant implication, though. According to Nichols, determining whether magnetic fields are necessary for habitability requires an understanding of the Earth's oldest magnetic field record. She is particularly curious about why Earth seems so special and whether the magnetic field plays a role.
The magnetosphere is a magnetic "bubble" created by Earth's magnetic field. It is a key element in human protection as it deflects and shields high-energy, damaging cosmic ray radiation constantly emitted during solar storms and traverses the universe.
Another component that interacts with the magnetosphere is the solar wind, a magnetic gas from the Sun. The magnetized solar wind interacts with the ionosphere and magnetosphere to cause space weather. In most cases, there is usually gentle solar wind and little to no space weather, thanks to the magnetosphere.
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