The near collapse of Earth’s magnetic field 591 million years ago may have allowed complex life to flourish

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Earth’s magnetic field plays a major role in making our planet habitable. A protective bubble above the atmosphere protects the planet from solar radiation, wind, cosmic rays and extreme temperature fluctuations.

However, Earth’s magnetic field nearly collapsed 591 million years ago, and ironically, this change may have played a pivotal role in the flourishing of complex life, a new study has found.

“In general, the field is protective. If we had not had a field early in Earth’s history, water would have been stripped from the planet by Earth.” Solar wind “(A stream of energetic particles flowing from the Sun toward Earth),” said John Tarduno, a professor of geophysics at the University of Rochester in New York and senior author of the new study.

“But in the Ediacaran, we had a remarkable period in the evolution of the deep Earth when the processes that create the magnetic field…became so inefficient after billions of years that the field almost completely collapsed.”

The study was published in the journal Earth and Environment Communications On May 2, it was found that the Earth’s magnetic field, created by Movement of molten iron in the Earth’s outer coreIt has been much weaker than its current strength for at least 26 million years. The discovery of the continuing weakening of the Earth’s magnetic field also helped solve an enduring geological mystery about when the Earth’s solid inner core formed.

This time frame is consistent with a period known as the Ediacaran Period, when the first complex animals appeared on the seafloor as oxygen in the atmosphere and oceans increased.

These strange animals hardly resemble life today, such as squash propellers, tubes, cakes, and discs Dickinsoniawhich reaches a size of 4.6 feet (1.4 metres), and Slow-like Kimberella.

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Before this time, life was largely single-celled and microscopic. The researchers believe that the weak magnetic field may have led to increased oxygen in the atmosphere, allowing early complex life to evolve.

Shuhai Xiao/Virginia Tech

An image shows a collection of a 560-million-year-old Dickinsonia costata fossil that was found in South Australia. With a length of more than a meter, this creature is the largest known animal of that period.

It is known that the intensity of the Earth’s magnetic field fluctuates over time, and crystals preserved in rocks contain small magnetic particles that are recorded in a record of the intensity of the Earth’s magnetic field.

The first evidence that Earth’s magnetic field weakened significantly during this period came in 2019 Study of rocks 565 million years old In Quebec, which indicated that the field was ten times weaker than it is today at that point.

The latest study collected more geological evidence indicating that the magnetic field was significantly weak, as information contained in a 591 million-year-old rock from a site in southern Brazil indicates that the magnetic field was 30 times weaker than it is today.

The weak magnetic field wasn’t always this way: the team examined similar rocks from South Africa dating back more than two billion years, and found that, back then, Earth’s magnetic field was as strong as it is today.

Unlike today, the innermost part of the Earth at that time was a liquid, not a solid, affecting the way the magnetic field was generated, Tarduno explained.

“Over billions of years, this process became less efficient,” he said.

“By the time we reached Ediacara, the field was on its last legs. It was about to collapse. But fortunately for us, it had gotten cold enough so that the inner core started generating (strengthening the magnetic field).”

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The emergence of the oldest complex life forms floating along the seafloor at this time is associated with rising oxygen levels. Some animals can survive at low levels of oxygen, such as sponges and microscopic animals, but larger animals with more complex bodies that move need more oxygen, Tarduno said.

Traditionally, the rise in oxygen during this time has been attributed to photosynthetic organisms such as cyanobacteria, which produced oxygen, allowing it to accumulate in the water steadily over time, explained study co-author Shuhai Xiao, a professor of geobiology at U.S. Virginia Tech.

However, the new research has proposed an alternative or complementary hypothesis that involves increased hydrogen loss to space when the Earth’s magnetic field is weak.

“The magnetosphere protects the Earth from the solar wind, thus keeping the atmosphere attached to the Earth. A weaker magnetosphere means the loss of lighter gases such as hydrogen from the Earth’s atmosphere,” Xiao added via email.

It is possible for multiple processes to occur simultaneously, Tarduno said.

“We do not challenge that one or more of these processes were occurring simultaneously. But the weak field may have allowed oxygen to exceed a threshold, which aided the evolution of animal radiation,” Tarduno said.

Peter Driscoll, a staff scientist at the Earth and Planetary Laboratory at the Carnegie Institution for Science in Washington, D.C., said he agreed with the study’s findings about Earth’s weak magnetic field, but the claim is that a weak magnetic field could affect oxygen in the atmosphere. Biological evolution has been difficult to assess. He did not participate in the study.

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“It is difficult for me to evaluate the validity of this claim because the impact that planetary magnetic fields may have on climate is not well understood,” he said via email.

Their hypothesis was “well-established,” Tarduno said, but proving causality would take decades of difficult work given how little is known about the animals that lived at the time.

Shuhai Xiao/Virginia Tech

A 565-million-year-old fossil of an Ediacaran animal, called Fractofusus Misrai, has been found in the False Point Formation in Newfoundland, Canada.

Geological analysis also revealed important details about the innermost part of the Earth’s center.

Estimates of when the planet’s inner core may have solidified — when iron first crystallized in the planet’s center — range from 500 million to 2.5 billion years ago.

the Research on the strength of the Earth’s magnetic field Indicates that age Earth’s inner core It is at the younger end of this time scale, where it solidified after 565 million years ago, allowing Earth’s magnetic shield to bounce back.

“The observations seem to support the claim that the inner core first formed shortly after this time, pushing the geodynamo (the mechanism that creates the magnetic field) from a weak, unstable state to a strong, stable dipole field,” Driscoll said.

The restoration of field strength after the Ediacaran, as the inner core grew, may have been important in preventing the water-rich Earth from drying out, Tarduno said.

As for the exotic animals of the Ediacaran period, they had all disappeared by the following Cambrian period, when The diversity of life exploded The branches of the tree of life familiar today were formed in a relatively short time.

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