Lunar samples brought back by China’s Chang’e-5 mission have revealed the nature of the protective shield the satellite once had. Rock fragments analyzed in laboratories showed that the Moon had a magnetic field during the first half of its life.
Currently, the Moon does not have a magnetic field like Earth’s. It directly receives all space radiation, which contributes to its hostility to life. However, astronomy has identified moons such as Ganymede, Europa and Callisto that do have magnetic fields. This phenomenon is not exclusive to planets, and as for the Moon, the idea of a magnetic field remained a possibility.
In 2020, the Chang’e-5 probe recovered 1.7 kilograms of lunar samples. They were the first brought to Earth since the Apollo era ended approximately 50 years ago. With current technology, space material has made it possible to understand the Moon from different perspectives, such as its volcanic past or the distribution of water in hydrated minerals.
The most recent contribution of this new stage of lunar exploration is the evidence of a weak and fluctuating magnetic field that enveloped the satellite. This shield, a product of the dynamo phenomenon in the satellite’s core, generated a field of 2 to 4 microteslas for at least 2,000 million years. Furthermore, Chinese scientists indicate that this field was only one-tenth of Earth’s current intensity during a period between 3,000 and 1,000 million years ago.
The research was led by the Institute of Geology and Geophysics of the Chinese Academy of Sciences. According to the study published in the journal Science Advancesthe basaltic remains analyzed showed a remanent magnetization generated by a magnetic field during the middle age of the Moon.
The remaining magnetization of the rocks will help understand the interior of the satellite. There cannot be a magnetic field without an internal motor, and this, on the Moon, could have been governed by the principle of the dynamo: converting mechanical energy from conductive fluids into electrical currents.
“This is compatible with dynamo models powered by long-lived energy sources, such as crystallization of the lunar core or differential movement of the mantle. The elixir of the Moon goddess seems to have done the trick,” the investigation mentions.
The Moon’s past will continue to be revealed as studies continue on new space samples. Scientists are particularly interested in those that arrived with the Chang’e-6 probe, extracted directly from the dark side of the satellite.
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