Fragments of lunar rocks from the American Apollo series spacecraft helped geologists to prove that the Moon possessed the same powerful magnetic shield as the Earth in the early eras of its existence, according to an article published in the journal Earth and Planetary Science Letters.
“We linked all the chemical and physical data in order to understand how the magnetic field appeared on the moon and how it could exist for so long. We created several synthetic versions of the Moon's core, using the latest data on its composition, and tested how they behave at the same pressures and temperatures that were in the depths of the Moon at the time, said Kevin Righter of the Space Flight Center. NASA named after Johnson in Houston (USA).
During the Apollo missions, American astronauts delivered lunar rock samples to Earth that bore traces of a magnetic field that is absent from the modern moon. On the other hand, the mass and dimensions of the Earth's satellite are too small for the appearance of a magnetic dynamo in its interior - flows of molten metal, which are the source of the magnetic field, in particular, on our planet.
The question arises: where did this field come from and why did it exist for more than a billion years? In search of a solution to this mystery, scientists formulated several ideas based on the chemical, isotopic and mineral composition of the rocks from the Apollo.
For example, in 2011, planetary scientists suggested that streams of metal could have arisen in the moon's core as a result of the fact that it was shaken after a collision with a large asteroid. Other groups of scientists said that the traces of the magnetic field in the samples from the Moon are an anomaly and that it did not have a strong magnetic field in the past.
Reiter and his colleagues decided to test all these theories by creating in the laboratory an analogue of the Moon's core from the rocks of which it is supposedly composed. To do this, scientists calculated the exact proportions of sulfur and carbon in the rocks delivered to Earth by the Apollo, and used them to determine the chemical composition of the core.
As NASA geologists explain, many of the Apollo rock fragments contain a large number of microscopic spheres, frozen droplets of molten rocks that fell on the surface of the Moon in the distant past along with streams of hot lava from the deep layers of its mantle. Knowing the ratio of sulfur to carbon in them, you can determine how many of these elements and some other substances contained in the core of the moon.
Recent measurements of this kind, carried out by Reiter's team, indicated the almost complete absence of both elements in the core of the Moon, which greatly changed the way the "dummies" of the core behaved during compression and increasing temperatures.
Promotional video:
By creating a pressure of 50 thousand atmospheres and raising the temperature to 1200-1700 degrees Celsius, NASA scientists came to the conclusion that the core of the Moon, consisting mainly of nickel and iron, could remain partially liquid even at such modest temperatures and pressures.
The middle of this core gradually crystallized and solidified, which made its liquid part move and generate a magnetic field comparable in strength to that of the earth. How long this dynamo worked and whether an asteroid was needed to "launch" it, scientists do not yet know, but all available data indicate that the process could occur by itself, due to the cooling of the core matter.
Why is it important? Similar processes could take place in the cores of other moons or small planets, whose mass was not enough to warm up the Earth-like core and launch a dynamo. The presence of a magnetic field is extremely important for the origin of life, and its presence in small moons may indicate that the conditions for the origin of life are more common than previously thought.