Scientists Uncover 3.7-Billion-Year-Old Record Of Earth’s Magnetic Field

Researchers at the University of Oxford and MIT have discovered a record of the Earth’s magnetic field dating back 3.7 billion years.

There has been an ongoing debate regarding the origin of the planet’s magnetic field, which protects its inhabitants from the relentless bombardment of charged particles emitted by the Sun.

Without the protective shield, charged particles or solar wind would have stripped away the Earth’s atmosphere.

To determine the time of the magnetic field’s formation, the researchers examined ancient iron-containing rocks from Isua, Greenland.

The Isua Supracrustal Belt is gradually emerging from the Greenland ice sheet, slowly revealing some of the oldest and best-preserved rocks found anywhere on Earth.

Finding evidence of magnetic field’s origin

Rebuilding the Earth’s magnetic field so far back in time has been challenging because various geological processes typically alter the preserved signals.

Interestingly, the Isua Supracrustal Belt has some exceptions. It is based on a strong continental crust that shields the rocks from intense tectonic activity and deformation. 

These rocks found here hold secrets about its strength and stability. This is because iron particles can act as tiny magnets, preserving the intensity of the magnetic field during the crystallization process.

As per the press release, the rocks dating back 3.7 billion years ago had a “magnetic field strength of at least 15 microtesla.” Interestingly, this intensity is “comparable” to today’s, which is 30 microtesla.

This discovery establishes the earliest estimate of the intensity of the Earth’s magnetic field. 

“Extracting reliable records from rocks this old is extremely challenging, and it was really exciting to see primary magnetic signals begin to emerge when we analyzed these samples in the lab,” said Claire Nichols, lead researcher from the University of Oxford. “This is a really important step forward as we try and determine the role of the ancient magnetic field when life on Earth was first emerging.”

It may have protected early life forms

The findings indicate that the Earth’s magnetic field has stayed relatively stable through billions of years. This stability played an important role in the emergence and evolution of life on our planet.

The research also indicates that the solar wind was likely much more powerful in ancient times. Over time, the strengthening of the Earth’s magnetic field may have protected the surface from the solar wind.

As a result, early life forms would have been able to leave the safety of oceans and migrate to the surface.

Furthermore, the research suggests that it may have influenced the development of our atmosphere. 

It is driven by the solidification of its liquid iron core. However, the planet’s core is estimated to have begun hardening just one billion years ago, implying that different processes existed before this point.

“A better understanding of the ancient strength and variability of Earth’s magnetic field will help us to determine whether planetary magnetic fields are critical for hosting life on a planetary surface and their role in atmospheric evolution,” the press release mentioned.

The findings have been published in the Journal of Geophysical Research.