Earth’s magnetic field 3.7 billion years ago was probably as strong as it is today, pushing back the earliest date for this planet’s protective bubble by 200 million years.
Magnetic fields came into play at the same time that life first appeared. Earth. Earth’s oldest fossils—bacterial mats called stromatolites— 3.5 billion years agosome researchers claim to have discovered that the history of stromatolites is related to 3.7 billion years.
The new study suggests that there was a protective magnetic bubble surrounding the Earth at that time that deflected cosmic radiation and destroyed charged particles from the sun.
However, the solar stream of charged particles was much stronger at that time, says Claire NichollsGeoscientist at the University of Oxford and lead author of the study, which was published on April 24 in ” Journal of Geophysical Research. Strong “solar winds” can strip away Earth’s protective magnetosphere, meaning Earth is far less shielded than it is today.This discovery contributes to the search for alien life.
“When we look for life on other planets, having a magnetic field is not necessarily the key,” Nichols told LiveScience. “Because actually, life still seems to be able to develop in a much smaller magnetosphere.”
The search for extraterrestrial life is just one reason to be curious Earth’s magnetic field. Not every planet has a magnetosphere, and researchers aren’t quite sure what makes Earth tick in the first place. Today, the magnetic field is driven by the stirring of the liquid portion of the Earth’s core and the transfer of heat from the solid inner core to the convective outer core as it cools.But researchers think the core isn’t until about a billion years ago.
Nichols and her team searched relentlessly for signs of ancient magnetic fields — 93 miles (150 kilometers) inland from Nuuk, Greenland, in a spot on the edge of the ice sheet that can only be reached by helicopter.
The rocks in this area, known as the Isua Crust Belt, are one of the oldest surviving parts of Earth’s crust. They contain iron-rich formations that preserve information about the direction and strength of magnetic fields when the rocks were formed.
Researchers can also look at folds in rocks caused by subsequent geological upheavals to see if the direction of the magnetic field matches that of the rocks. If not, then the magnetic field predates those geological events, whose ages researchers generally know.
Using these methods, the researchers found that 3.7 billion years ago, magnetic field strengths were at least 15 microtesla. This is half of today’s average magnetic field strength. But that’s a lower estimate, so the field could have been just as strong then as it is now, Nichols said.
“Whatever is driving the core’s magnetic field is just as strong before the core solidifies,” Nichols said.
Researchers are now interested in delving deeper into the connection between ancient magnetic fields and Earth’s atmosphere. About 2.5 billion years ago, the atmosphere suddenly experienced massive oxidation.This is partly due to photosynthesisBut the strength of the magnetic field affects which gases stay in the atmosphere and which escape into space, Nichols said.
“I really wanted to know whether magnetic fields played a role in the evolution of Earth’s atmosphere over time,” Nichols said.
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