Recent research brings a surprising twist to our understanding of planetary science. This new study indicates that a significant weakening of Earth’s magnetic field around 590 million years ago might have played a critical role in the development of complex life forms.
Although the first life on Earth appeared at least 4 billion years ago, prior to this anomaly in the magnetic field, life forms were microscopic, primitive, and largely static.
The 26-Million-Year Anomaly That Changed the Course of Life
The Earth’s magnetic field has flipped its direction multiple times over millions of years. But between 591 and 565 million years ago it experienced an extended period of weakening.
According to a new study published in Communications Earth & Environment, this prolonged weakening of the magnetic field might have been instrumental in allowing for significant changes in Earth’s atmosphere. In turn, this would have supported the evolution of more complex life forms.
The study’s findings are based on an analysis of plagioclase crystals from the Passo da Fabiana Gabbros in Brazil, which date back to the beginning of this critical period. Crystals preserve ancient magnetic fields by capturing and locking in the orientation of magnetic minerals at the time of their formation, allowing scientists to study the Earth’s magnetic history.
These crystals suggest that the geomagnetic field strength was at its lowest — only one-thirtieth of today’s levels and considerably weaker than any previously recorded. Such a drastic decrease in geomagnetic strength is thought to have lasted for at least 26 million years, covering one of the most crucial epochs in the history of life on Earth.
The Connection Between Magnetic Fields and Life
While the primary role of Earth’s magnetic field has been to shield our planet from solar wind and cosmic radiation, thus protecting our atmosphere, the study proposes that its temporary weakening might have actually benefited our biosphere.
Although counter-intuitive, this makes sense. The diminished field could have led to an increased escape of hydrogen from the atmosphere. This process could decrease the amount of hydrogen available to bond with oxygen. And so, this might have led to higher oxygen levels in the atmosphere.
Oxygen is critical for the development of complex life and the first truly mobile and complex creatures, known as the Ediacaran fauna, emerged shortly after this period of reduced magnetic field strength. These creatures represented a significant departure from the mostly microscopic and stationary life forms that had dominated the Earth previously.
Ediacaran fauna are remarkable. The disk-shaped Aspidella could be early ancestors of jellyfish. The leaf-like Charnia was an iconic frondose organism whose precise biological associations remain mysterious but might suggest a relation to algae or early animals. Another intriguing example is the half-billion-year-old Dickinsonia, an oval, ribbed creature that grew by adding segments.
Ongoing study of life
The increased oxygen that might have resulted from this magnetic weakening is still a subject of intense research and debate. Theoretical models vary widely, predicting an increase in hydrogen loss ranging from 30% to an astonishing 1,000%.
The study also touches upon other secondary effects of a weaker magnetic field. For example, increased levels of nitrogen oxides from heightened solar radiation. This could have led to the creation of ozone holes, similar to those caused by human-made chlorofluorocarbons (CFCs), further altering Earth’s atmospheric chemistry.
While the direct cause of Earth’s magnetic field weakening during this period remains unclear, the potential consequences of such an event provide fascinating insights into the complex interplay between geomagnetic fields and life. This research not only deepens our understanding of Earth’s geological and biological history but also might guide the search for life on other planets.
