(ORDO NEWS) — The rock samples brought to Earth by the Apollo program between 1968 and 1972 provided a wealth of valuable information about the history of the Moon, but they also raised a number of questions, some of which remain unresolved to this day.
Thus, the analysis of stones showed that some of them were formed in the presence of a powerful magnetic field – comparable in strength to the Earth’s magnetic field. However, scientists still cannot understand how such a powerful magnetic field could form around a body the size of the Moon.
In a new study, geologists from Brown University, USA, led by Alexander Evans, offer a possible solution to this problem. According to their model, giant rock formations sank into the liquid mantle all the way to the core, and such internal convection could cause powerful magnetic fields to temporarily form. These processes could proceed intermittently during the first billion years of the Moon’s history.
Planetary bodies generate magnetic fields through a process known as dynamos. The slow dissipation of heat causes convection of molten metals in the planet’s core. Constant stirring of electrically conductive material causes a magnetic field. This is how the Earth’s magnetic field is formed, which protects us from the most dangerous radiation emitted by the Sun.
According to models of the Moon’s core, it was too small to provide the convection needed to form a permanent strong magnetic field. However, as Evans shows, in the liquid magma that covered the entire surface of the Moon in the first million years after its formation, after the initial precipitation of the heavy minerals olivine and pyroxene, the remaining melt was enriched in titanium.
As a result, a secondary mineral sediment was formed, which also crystallized in the form of a crust near the surface, broke under its own weight into fragments with a diameter of about 60 kilometers each, and fragment by fragment sank to the core for one billion years. When a relatively cold fragment fell onto a hot core, convection in the core sharply increased, which led to a flash of magnetic field intensity,
According to the author, the model proposed by his group is testable, and for its verification it is necessary to study the rocks delivered by the Apollo mission not only for the presence of minerals formed in the presence of powerful magnetic fields, but also for the presence of minerals formed in the “intermediate” periods between peaks in field intensity when the Moon’s magnetic field returned to a low level.
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