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A joint study by the University of Oxford and the Massachusetts Institute of Technology has uncovered a 3.7 billion-year-old magnetic field record in Greenland. It is due to
A joint study by the University of Oxford and the Massachusetts Institute of Technology has uncovered a 3.7 billion-year-old magnetic field record in Greenland. It is due to cosmic and solar effects. radiation.
A new study has restored a 3.7-billion-year-old record of Earth’s magnetic field and found that it is remarkably similar to the field surrounding Earth today. The findings were published today (April 24). Journal of Geophysical Research.
Life on Earth would be impossible without its magnetic field, as it protects us from harmful cosmic radiation and charged particles emitted by the Sun (“solar wind”). However, until now, the exact date when the modern magnetic field was first established was not known.
In a new study, researchers examined a sequence of ancient iron-bearing rocks found in Isua, Greenland. The iron particles effectively act like tiny magnets that can register the strength and direction of the magnetic field as the crystallization process locks them in place. The researchers found that rocks dating back 3.7 billion years ago captured a magnetic field of at least 15 microtesla, comparable to today’s magnetic field (30 microtesla).
These results provide the earliest estimate of the Earth’s magnetic field strength obtained from whole rock samples, providing a more accurate and reliable estimate than previous studies using single crystals.
Principal investigator Professor Clare Nicholls (Department of Earth Sciences, University of Oxford) said: “It is extremely difficult to get a reliable record from such ancient rocks, and it was really exciting to see primary magnetic signals start to emerge as we analyzed these samples in the laboratory. “It’s a really important step forward in trying to determine the role of the ancient magnetic field when life was just beginning on Earth.”
Although the magnetic field strength appears to have remained relatively constant, the solar wind is known to have been much stronger in the past. This suggests that Earth’s surface protection against the solar wind has increased over time, possibly allowing life to move to the continents and leave the protection of the oceans.
The Earth’s magnetic field is created by mixing molten iron with a liquid outer core, acting with buoyancy as the inner core solidifies, creating a dynamo. A solid inner core had not yet formed during Earth’s early formation, leaving open questions about how the early magnetic field was maintained. These new results show that the mechanism that drove Earth’s first dynamo was as effective as the solidification process that creates Earth’s magnetic field today.
Understanding how Earth’s magnetic field strength changes over time is also key to determining when Earth’s solid inner core began to form. This will help us understand how quickly heat escapes from deep within the Earth, which is key to understanding processes such as plate tectonics.
A significant difficulty in reconstructing the Earth’s magnetic field at a time in the past is that any event that heats the rock can alter the preserved signals. Rocks in the Earth’s crust often have a long and complex geological history that erases previous information about the magnetic field. However, the Isua Supracrustal Belt has a unique geology; It lies on top of a thick continental crust that protects it from major tectonic activity and deformation. This allowed researchers to establish clear evidence for the existence of a magnetic field 3.7 billion years ago.
The results may also provide new insights into the role of our magnetic field in shaping the development of the Earth’s atmosphere as we know it, particularly the escape of gases from the atmosphere. A currently unexplained event is the loss of inactive xenon gas in our atmosphere 2.5 billion years ago. Xenon is relatively heavy and therefore unlikely to fly away from our atmosphere. Recently, scientists have begun to investigate the possibility of removing charged xenon particles from the atmosphere by a magnetic field.
In the future, researchers hope to expand our knowledge of the Earth’s magnetic field to the rise of oxygen in the Earth’s atmosphere about 2.5 billion years ago by studying other ancient rocks from Canada, Australia and South Africa. Better understanding the ancient strength and variability of the Earth’s magnetic field will help us determine whether planetary magnetic fields are vital to the existence of life on planetary surfaces and their role in the evolution of the atmosphere.
Source: Port Altele
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