3.7 Billion-Year-Old Rocks in Greenland Preserve Earth's Ancient Magnetic Field

In a groundbreaking discovery, geologists from MIT and Oxford University have found 3.7 billion-year-old rocks in Greenland that preserve Earth's ancient magnetic field. The findings, published in the Journal of Geophysical Research, suggest that the magnetic field surrounding our planet was already in place at least 3.7 billion years ago, potentially extending the field's age by 200 million years.

The ancient magnetic field, with a strength of at least 15 microtesla, appears remarkably comparable to the field surrounding Earth today. This discovery sheds light on the early habitability of our planet, as a strong magnetic field helps protect it from harmful solar radiation, making it more hospitable for life to emerge and thrive.

The researchers sampled rock formations from the Isua Supracrustal Belt in Greenland, which contain iron oxide minerals that can preserve the orientation of the magnetic field at the time of their formation. By studying the iron particles in these ancient rocks, which acted as natural magnets, the team was able to determine the magnetic field's strength and direction 3.7 billion years ago.

Why this matters: This discovery provides the oldest estimates of Earth's magnetic field strength and suggests that the magnetic field has remained comparable over the last billions of years, potentially allowing life to emerge from the oceans to land. Understanding the evolution of Earth's magnetic field and its role in supporting life on early Earth is vital for our knowledge of planetary habitability.

The findings raise questions about how Earth's early magnetic field was generated, as the solid inner core had not yet formed at that time. The researchers plan to excavate ancient rocks from other locations to further study the evolution of the magnetic field and its potential influence on the development of Earth's atmosphere, particularly the major oxygenation event around 2.5 billion years ago.

"This is the oldest undisputed evidence of Earth's magnetic field, potentially extending its age by 200 million years," said one of the researchers involved in the study. "The findings shed light on the early Earth's habitability, as the magnetic field is essential for protecting life from harmful cosmic radiation."

Key Takeaways

• Geologists found 3.7 billion-year-old rocks in Greenland with Earth's ancient magnetic field
• The magnetic field's strength was comparable to today's, potentially extending its age by 200 million years
• A strong magnetic field helps protect Earth from harmful solar radiation, supporting early life
• The findings raise questions about how the early magnetic field was generated without a solid inner core
• Researchers plan to study more ancient rocks to understand the magnetic field's evolution and impact on Earth's atmosphere