Earlier this week, astrophysicists from the Institute of Geophysics in Paris denied the version of the origin of the moon, which was still considered the most likely. According to this hypothesis, about 4.5 billion years ago, the still very young Earth collided with the protoplanet Theia, as a result of which the Moon was formed. Computer simulations carried out by specialists have cast doubt on this version, as well as many of our other ideas about the origin of the space body closest to Earth.
The MIR 24 editors chose the main versions of the origin of the satellite and, together with experts, weighed the pros and cons of popular hypotheses.
Version # 1: one giant collision
The lunar impact formation model has remained dominant in science for the past three decades. Astrophysicists accepted it almost unanimously after the Apollo 17 lunar module delivered more than 110 kg of lunar rocks to Earth during the last landing on the satellite in December 1972.
Analysis of the chemical and isotopic composition of the soil led scientists to the idea that at the early stage of the formation of the solar system, the Earth could collide with a large celestial body - a protoplanet, the dimensions of which were commensurate with today's Mars, that is, approximately 10.7% of the mass of the Earth.
“For both celestial bodies, this event was catastrophic, and the material that was ejected as a result of this collision, for many millennia, partially remained in the orbit of the Earth, due to which, as a result of evolutionary compression, an earth satellite was formed,” says Doctor of Physical and Mathematical Sciences Alexander Rodin, Senior Researcher at the Space Research Institute of the Russian Academy of Sciences.
The names of the heavenly bodies are traditionally given Greek, mythological. Therefore, the hypothetical protoplanet was named in honor of one of the titanid sisters Teia, who, according to the beliefs of the ancient Greeks, was the mother of Selene (the Moon). The connection between the Earth and the satellite turned out to be so strong that over time, the Moon began to cause ebb and flow on the Blue Planet. This, in turn, formed the conditions for the emergence of the first elements of biological life (nucleotides) from the simplest nitrogenous compounds, a mixture of phosphate and carbohydrates, on the wet ground. Thus, under the influence of lunar activity and sunlight, the first "laboratory" for the formation of future life was formed on the earth's surface.
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The mega-explosion theory is supported by the fact that the core of the Earth's satellite is too small for a planet that formed simultaneously with the Earth (the radius of the Moon's core is about 240 kilometers). In addition, the composition of the Moon is much more homogeneous than our planet. Everything seemed to persuade scientists to the point of view that the reason for the birth of the moon was the proto-beauty Teia.
The astronomers of the Paris Institute of Geophysics were suspicious of the validity of such a beautiful hypothesis. Confused by the chemical composition of the earth's mantle and lunar soil. Something was wrong there. As a result, Parisian astronomers launched a multi-year experiment that has just ended. During this experiment, they conducted 1.7 billion computer simulations of the collision of the Earth and Theia and found that the mass of a hypothetical celestial body that the Earth collided with could not be more than 15% of the mass of our planet.
Otherwise, the earth's mantle would contain many times more nickel and cobalt, and light isotopes of radioactive elements that are present in it now, for example, the isotope of helium-3, would have long since evaporated from the lunar soil.
Version # 2: multiple bombing theory
"The latest French research confirms the assumption that the collision was not one - there were many," explains Dr. Rodin, "The future material for the formation of a satellite accumulated over millions of years in Earth's orbit, and the bombers themselves were much smaller than the hypothetical Theia." …
However, according to the scientist, this discovery did not make an epoch-making revolution. In recent decades, the Moon has remained not only the most studied, but also the most actively studied object in the solar system. Every year, scientists receive more and more new data at the disposal of scientists that refute one or another of the existing hypotheses.
“Computer simulations only help us to simulate certain conditions. Meteorologists work in about the same way, determining the weather for the near future. But we are well aware that even the forecast for tomorrow may be wrong. What can we say about such global events as the birth of living matter, the formation of the Moon or the Earth,”the scientist noted.
The doctor of physical and mathematical sciences, head of the department for the study of the moon and planets at the Institute named after P. K. Sternberg Moscow State University Vladimir Shevchenko. According to him, the French astrophysicists were several years ahead of the Russian scientist, director of the V. I. Vernadsky Institute of Geochemistry, Eric Galimov, who analyzed the hypothesis of the protoplanet Teil and was one of the first in world science to be able to reasonably refute it. True, purely theoretically. Now his theory has received experimental confirmation.
Version number 3: "sister" hypothesis
The hypothesis, to which many Russian scientists are inclined today, sounds like this: the Moon and the Earth were formed relatively simultaneously from a single cloud of gas and dust. This happened about 4.5 billion years ago, which is confirmed by the data of radioisotope dating of meteorite samples, the so-called chondrites.
The “embryo” of the Earth attracted to itself the maximum number of particles in the zone of their availability, and from the remaining fragments in orbit a satellite, smaller in size, but similar in chemical composition, was formed.
“This theory removes dubious questions about the geochemical parameters of the lunar soil,” explains Vladimir Shevchenko. “If a mega-impact took place, the Moon would have to contain the same substance that the Earth consisted of at the moment and would be much more similar to the Earth than it is now,” the professor sums up.
True, such a beautiful hypothesis about the common progenitor cloud does not explain much. For example, why the lunar orbit does not lie in the plane of the earth's equator and why its iron-nickel core was formed so miniature in comparison with ours.
Version number 4: planet-captive, or "conjugal" hypothesis
One of the most curious hypotheses, while having the least amount of evidence, is the hypothesis that the Moon was originally formed as an independent planet in the solar system. As a result of the deviation of the celestial body from the orbit (the so-called perturbations), the planet, so to speak, "lost its course" and entered an elliptical orbit intersecting with the Earth. During one of the approaches, the Moon fell into the field of earth's gravity and turned into its satellite.
American astronomers under the leadership of Thomas Jackson C were interested in this theory not for academic reasons. The fact is that the legends of the ancient African people of the Dogon told about the times when there was no second star in the night sky - the Moon.
Despite the fact that the theory did not fit into the "Big Three" academic hypotheses about the origin of the satellite, it was seriously discussed by a group of scientists led by Sergei Pavlovich Korolev when designing a descent automatic station.
Scientists had to "blindly" decide how the moon was formed. The success of landing the station depended on their conclusions. After all, if the Moon revolves around the Earth for billions of years, without a dense atmosphere on its surface, a multi-meter layer of dust falling from space should have accumulated. If that were the case, the station intended to land on the Lunar firmament would simply have drowned.
Scientists clearly liked the assumption that the Moon was captured by the Earth relatively recently. In this case, its surface should still be solid. Therefore, the landing apparatus decided to rely on this very scenario.
True, this theory has more contradictions than other versions of the origin of the satellite. For example, why do oxygen isotopes on the Moon and Earth have such an identity? Or why the Moon rotates in the same direction with the Earth, while the moons captured by Jupiter - Io, Europa, Ganymede and Callisto - rotate in retrograde, that is, the opposite direction from Jupiter.
Be that as it may, even relatively “foldable” and “attractive” hypotheses do not give an accurate description of how exactly the night star arose on the earth's horizon. However, such inconsistencies are observed when describing any other physical phenomenon of this scale, notes Alexander Rodin. Each new discovery, even carried out in terrestrial conditions, can at any time call into question any hypothesis "established" in science. Even about the origin of the Earth - not like its satellite.
Nadezhda Serezhkina