Earth’s ancient weak magnetic field may have fueled the rise of life

Fossil impression of Dickinsonia, an example of Ediacaran fauna, found in present-day Australia. Credit: Shuhai Xiao/Virginia Tech.

Millions of years ago, during a period called the Ediacaran, from about 635 to 541 million years ago, Earth experienced a dramatic increase in complex, multicellular life forms.

This time marked a critical turning point, paving the way for the diverse life we see today. But what caused this surge in life forms?

Recent research points to an unexpected factor: a weak magnetic field.

Published in Nature Communications Earth & Environment, the study led by Professor John Tarduno from the University of Rochester, suggests that fluctuations in Earth’s ancient magnetic field may have played a crucial role in creating conditions favorable for life to flourish.

The research team focused on the intriguing Ediacaran fauna, some of the earliest large-scale life forms, which displayed characteristics similar to modern animals and required more oxygen than their predecessors.

Usually, Earth is shielded by a strong magnetic field generated by liquid iron swirling around in the planet’s outer core.

This magnetic field protects the Earth from harmful solar radiation. However, the data from ancient rocks suggests that during the Ediacaran Period, the magnetic field was up to 30 times weaker than today and remained exceptionally low for about 26 million years.

A weak magnetic field would allow more solar radiation to reach Earth, stripping away hydrogen atoms from the atmosphere.

This process potentially left behind more oxygen, as hydrogen would typically react with oxygen to form water vapor.

With less hydrogen, more oxygen could accumulate in the atmosphere and the oceans, possibly supporting the development of more complex life forms that thrived during this period.

Using advanced techniques, Tarduno’s team examined the strength of the ancient magnetic field. They analyzed magnetism preserved in feldspar and pyroxene crystals from anorthosite rocks, using tools like a CO2 laser and a superconducting quantum interference device (SQUID) magnetometer.

These methods allowed them to pinpoint the magnetic field’s intensity throughout the Ediacaran Period with great accuracy.

The findings suggest that the weak magnetic field could have been a catalyst for increasing oxygen levels, setting the stage for the evolution of diverse and complex organisms.

Interestingly, the magnetic field strength recovered in the subsequent Cambrian Period, a time when even more animal groups appeared, indicating a restored and more protective magnetic field conducive to life proliferation.

The study not only sheds light on a pivotal time in Earth’s biological history but also highlights the interconnectedness of geological and biological processes.

Understanding how Earth’s interior and its magnetic field have influenced life’s evolution provides valuable insights into the conditions necessary for life both on our planet and potentially on others.

Supported by the National Science Foundation, this research underscores the importance of Earth’s core processes in the broader narrative of life’s history and suggests intriguing possibilities for life’s potential on other planets with similar conditions.

Source: University of Rochester.