A collaborative study by the University of Oxford and MIT has uncovered a remarkable discovery regarding Earth’s ancient magnetic field. The researchers have found a 3.7-billion-year-old magnetic field record from Greenland, which demonstrates that Earth’s magnetic field was as strong as it is today. This finding is crucial because the magnetic field plays a vital role in protecting life by shielding once morest cosmic and solar radiation.
The study examined an ancient sequence of iron-containing rocks from Isua, Greenland. These rocks contain iron particles that act as tiny magnets, recording both the magnetic field strength and direction during the process of crystallization. The researchers discovered that rocks dating from 3.7 billion years ago captured a magnetic field strength of at least 15 microtesla, comparable to the modern magnetic field’s strength of 30 microtesla.
This new study provides the oldest estimate of Earth’s magnetic field strength derived from whole rock samples. Previous studies relied on individual crystals, which were less accurate and reliable. The similarity between the ancient magnetic field and the present-day magnetic field indicates that Earth’s magnetic field strength has remained relatively constant over time.
While the magnetic field strength has remained consistent, the solar wind, which is a stream of charged particles emitted by the Sun, is known to have been significantly stronger in the past. This suggests that Earth’s surface protection from the solar wind has increased over time, allowing life to move onto the continents and away from the oceans’ protection.
Earth’s magnetic field is generated by the mixing of molten iron in the fluid outer core. As the inner core solidifies, buoyancy forces create a dynamo that generates the magnetic field. During Earth’s early formation, when the solid inner core had not yet formed, there were questions regarding how the early magnetic field was sustained. The new results suggest that the mechanism driving Earth’s early dynamo was as efficient as the process that generates Earth’s magnetic field today.
Understanding how Earth’s magnetic field strength has varied over time is also crucial for determining when Earth’s inner core began to form. This information is essential for understanding processes such as plate tectonics and how heat escapes from Earth’s deep interior.
Reconstructing Earth’s magnetic field from billions of years ago is challenging due to events that can alter the preserved magnetic field information. However, the unique geology of the Isua Supracrustal Belt in Greenland, with its thick continental crust, has protected the rocks from extensive geological activity and deformation. This allowed the researchers to build a clear body of evidence supporting the existence of the 3.7-billion-year-old magnetic field.
The implications of this research extend beyond Earth’s ancient magnetic field. It may provide new insights into the role of our magnetic field in shaping Earth’s atmosphere. Scientists have been studying the unexplained loss of the gas xenon from our atmosphere over 2.5 billion years ago. One possibility is that charged xenon particles were removed from the atmosphere by the magnetic field.
In the future, researchers hope to expand our knowledge of Earth’s magnetic field by examining other ancient rock sequences in Canada, Australia, and South Africa. A better understanding of the ancient strength and variability of Earth’s magnetic field will help determine its role in hosting life on a planetary surface and shaping atmospheric evolution.
The findings from this study have significant implications for our understanding of Earth’s magnetic field and its role in supporting life. They highlight the importance of continued research into the ancient magnetic field and its interactions with Earth’s atmosphere. By studying Earth’s magnetic history, scientists can gain insights into the processes that have shaped our planet and potentially apply this knowledge to other planetary bodies. This research opens up new possibilities for future discoveries and advances in our understanding of Earth’s magnetic field.