Scientists concluded that the real history of the magnetic shield of our satellite lasted only a few hundred million years.
The moon was formed about 4.5 billion years ago, from material ejected into orbit after the collision of the Earth with a massive celestial body. At first, the satellite was molten and had its own magnetic shield, traces of which can be found today in local minerals. Its magnetosphere was much weaker than Earth’s and dissipated when the iron-bearing rocks in the interior of the moon cooled.
This process took place faster than previously thought so that the magnetic field disappeared no later than four billion years ago. These are the conclusions reached by the authors of a new article published in the journal Science Advances.
Everything new you need to know about the Moon’s supposed magnetic shield
Did the Moon ever have a magnetic shield?
There has been a long-lasting debate over whether or not our satellite may have had a magnetic shield for a prolonged period of time billions of years ago.
Impossible to last long
Indeed, the Moon’s magnetosphere could not last long. The iron-containing core of the satellite is very small and cooled down quickly, losing the ability to generate a magnetic field using the dynamo mechanism.
Span of existence
However, until now, the timing of its existence remained unclear. Therefore, the authors of the new work analyzed samples of lunar minerals dated at different times.
Traces of magnetism
In rocks aged from 3.2 to 3.9 billion years, traces of magnetism were no longer found. Unexpected magnetism was demonstrated by a sample of volcanic glass formed by a meteorite falling just about two million years ago. However, John Tarduno and his colleagues at the University of Rochester showed that matter could acquire magnetic properties due to temporal fields generated briefly in the collision plasma.
Determining the correct age of the magnetosphere
According to scientists, the appearance of such extremely young magnetized samples may give an incorrect determination of the age of the magnetosphere.
However, by themselves, they cannot testify to its existence in such a recent past of the Moon.
As a result, Tarduno and his co-authors concluded that the real history of the magnetic shield in our satellite lasted only a few hundred million years, and about four billion years ago it had already disappeared.
What does the lack of a magnetic shield mean?
Scientists note that without the protection of the Moon’s magnetic field, the lunar soil might be full of chemical elements and compounds brought by the solar wind.
Examples include carbon, hydrogen, certain isotopes of helium, and even water. Some of these elements and compounds that might be abundant on the Moon are definitely rare here on Earth.
Scientists have high expectations for the upcoming missions to the moon which should begin in 2024 with the Artemis program. Apart from the recent Chinese mission that returned samples from our satellite, the last samples were collected decades ago during the years of the Apollo program.
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• Gramling, C. (2021, August 4). A lunar magnetic field may have lasted for only a short time. Science News.
• Phys.org. (2021, August 5). Lunar samples solve mystery of the moon’s supposed magnetic shield.
• Sparkes, M. (2021, August 4). The moon may never actually have had a strong magnetic field. New Scientist.
• Tarduno, J. (2021, August 5). Moon lacked a magnetic field for nearly all its history – new Research resolves MYSTERY sparked by rocks brought back on Apollo. The Conversation.
• University of Rochester. (2021, August 4). Lunar samples solve mystery of the moon’s supposed magnetic shield.