Japanese probe confirms the theory of the Russian physicist about the formation of the moon

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Japanese probe confirms the theory of the Russian physicist about the formation of the moon
Japanese probe confirms the theory of the Russian physicist about the formation of the moon
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The lunar surface turned out to be rich in carbon, a relatively light element that could not have survived in the material of the Earth's satellite if it had formed after the collision with Theia. This means that neither this hypothetical planet, nor the mega-impact of the Earth itself has ever happened with it. The moon, on the other hand, arose by a fundamentally different mechanism, discovered in 2007 by physicist Nikolai Gorkav. Moreover, in such a scenario, this celestial body is more suitable for colonization by earthlings. Let's figure out why.

Planet with rings

The mystery of the birth of the moon: how the landing on the satellite gave rise to the hypothesis of a mega-impact

The planets of the solar system were formed in relatively similar ways - from a protoplanetary disk, similar to which astronomers find in other stars today. During the formation of a planet in one or another orbit, it acts like a vacuum cleaner there: it attracts all planetesimals (small protoplanetary bodies).

Sooner or later, almost all of them must fall to the planet. The only exception can be small bodies, close in size to Deimos, but the Moon is so large that it cannot be built out of such small "crumbs".

A natural question arises: how did our companion appear (since the word "moon" is feminine)? From the above, it is obvious: this could have happened only after the end of the formation of the Earth and exclusively due to some powerful external forces - by themselves, pieces of the Earth will not come off and will not fly into the sky (although in the 19th century there was such a somewhat naive hypothesis).

It is enough to look at the Moon through good binoculars, so that the thought of the source of these mysterious external forces comes to mind by itself. The satellite is covered with a mass of craters - traces of falling asteroids.

Maybe a bunch of asteroids flew into Earth's orbit, which then gradually collided with each other, their debris created a semblance of the rings of Saturn, and then lost speed and, due to weak collisions, formed the Moon? This hypothesis was put forward in 1975 by the Soviet astronomer Yevgenia Ruskol, but, alas, did not survive the analyzes of the lunar soil.

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The fact is that the samples of "Apollo" and the Soviet "Luna-24" showed that the ratio of isotopes of different elements in the lunar and terrestrial soil is almost indistinguishable.

This means that the Earth's satellite could not form in any way mainly from asteroids that arrived from other parts of the solar system. After all, different parts of the protoplanetary disk have different ratios of the isotopes of certain elements. This can be easily traced from analyzes of the Martian soil or meteorites that are found on Earth.

In addition, in the matter of the planets, heavy elements easily go down into the core, there are few of them in the mantle. The lunar surface showed a "terrestrial" deficiency of heavy elements - for example, iron. But in asteroids, heavy elements do not go anywhere - they are too low-mass for this.

It goes without saying that the moon should have been formed mainly from earthly material - but how?

American scientists William Hartman and Donald Davis in the same 1975 proposed an extremely intriguing mega-impact hypothesis. Along it, the planet Theia collided with the ancient proto-Earth about 4.5 billion years ago.The impact threw a lot of debris from our planet into Earth's orbit, and they were seriously heated by the impact event, whose energy, according to calculations, should have been at least trillions of megatons.

There were two important consequences of this hypothesis. First, the Earth had to lose its primary ocean - it literally boiled away after the impact. Secondly, the Moon, whose components after the megaimpact were warmed up even stronger than the Earth's (up to thousands of degrees), should have lost all water in general. And equally - all the light elements.

Earth Scientists Strike Back at Theia

For twenty-five years it seemed that everything was clear with the formation of the moon. It was not for nothing that we used the word it seemed: in the same lunar soil, delivered by Apollo and Luna-24, we found water, which is not particularly compatible with the heating of the components of the Earth's satellite from an explosion of trillions of megatons.

But the question was resolved simply: the US lunar program was developed in a hurry, so the containers for soil from the satellite were made not particularly successful there: they were leaky (regolith spilled out of them during transportation). The water in them was attributed to the contamination of samples already on Earth. He was also credited with the data of the Apollo ion detectors, which also showed water in the lunar soil.

The Soviet samples were in normal containers, so you can't blame it on anything. But something else helped: in the West, no one noticed the corresponding Soviet work.

And yet, problems arose - and it was precisely in the strength of the mega-impact, calculated as a minimum of trillions of megatons. Already in the 21st century, a series of observations from the orbit of the Moon showed that a very thick layer of water ice was present in the circumpolar craters of the satellite. According to the latest estimates for 2019, there is 100 billion tons of it.

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Here it should be borne in mind that we are talking only about what is on the surface, in the craters. Water ice in huge lava tubes (lunar caves up to kilometers in diameter) cannot be estimated from orbit, and its amount may be noticeably greater.

Of course, it is difficult to reconcile with the hypothesis of "dry sublimation" as a means of obtaining lunar material from earth material, knocked out by Theia. When heated, water evaporates quickly and easily, and the typical speed of its molecule is so high that the debris simply cannot hold it with their gravity.

Objections were also received from Earth explorers. The blow of the force necessary for the formation of the Moon was unambiguously supposed not only to evaporate the oceans, but also to arrange lava seas on Earth for some time: to melt the upper layers of the planet. However, geologists unequivocally argue that there are no traces of lava seas on our planet - not just a global lava ocean, but even local ones.

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To close the question of lunar water, the idea was proposed that it was brought there by comets from the outer regions of the solar system. True, it turns out that the comets should have flown to the Moon by a conveyor belt: according to the calculations of Russian scientists, at least 95% of the material when a comet hits our satellite should be thrown back into space.

It turns out that comets brought at least trillions of tons of water to the Earth's satellite - a very strange result, given that the gravity of the nearby Earth should intercept most of the comets passing through this region of the system.

Was Theia there?

In 2007, the first alternative explanation of the problems of the mega-impact hypothesis appeared. Nikolai Gorkavy published an article "Formation of the Moon and Binary Asteroids", where he showed that a completely different mechanism of the birth of our satellite is possible.

He called his model "multiimpact" and suggested that it may be a typical mechanism for the formation of large satellites - not only the Earth's Moon, but also Charon near Pluto, and even double asteroids.

The essence of the multiimpact model is on the assumption that the earth's satellite was built not by one giant collision, but by many smaller ones. A fairly large asteroid hitting Earth is definitely knocking debris out of it.

But since the collision energy is small in this case, no lava seas are formed on Earth in this case. And the discarded debris does not completely melt: their central parts may not even reach the boiling point of water.

After entering the near-earth orbit, such debris had two options for their further fate. The fact is that at an early stage in the history of our planet, a low-mass protosatellite disk should have rotated around it, and in the same direction as our planet.

After a large asteroid fell to the Earth, those terrestrial debris that were thrown out in the direction of the planet's rotation, as it were, "added up" with this disk. But those debris that flew out of the atmosphere "against the grain" lost their energy from a collision with the protosatellite disk. An object in orbit that loses its energy inevitably falls - that is, such debris returned to our planet.

And the "defectors" with time could seriously raise the mass of the protosatellite disk - up to a value of 1% of the mass of the entire Earth or even higher.

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Stop-stop, the reader will say. But what about the banal logic? If we shoot into space from an electromagnetic accelerator, the body will either fly away from the vicinity of the Earth, or eventually fall to its surface.

Let's say that this is exactly what will happen to all artificial satellites of the Earth: over time, they will slow down on the dust of near-earth space and still fall onto the planet. How does it suddenly happen that the debris resulting from the collision of the Earth with ancient asteroids "hovered" in the sky for 4.5 billion years, forming into the Moon?

This is where the main merit of the multi-impact model lies. Indeed, a piece of the Earth itself cannot stay in orbit for billions of years. But when Gorkavy calculated the interaction of this debris with the ancient protosatellite disk, it turned out that the situation was changing radically.

Although the ancient disk was low-mass, it had stable orbits of its bodies. When the debris knocked out of the Earth by the next asteroid and flying "along the wool" caught up with any of the bodies of the protosatellite disk, they collided with it and gave it part of their energy.

As a result, the forming Moon from the protosatellite disk could not fall to the Earth: it was all the time slightly "thrown" by the impact of new debris. As a result, part of the "pushing" earthly debris fell on the planet, and part on the proto-Moon, adding mass to it. Over time, in this scenario, the Moon should begin to move away from the planet, as we observe in practice.

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The total number of asteroids needed to form a lunar-sized body from debris knocked out of the Earth seems to be quite large - there could be millions of them. And we are talking about bodies with a diameter of 10 to 1000 kilometers.

Now such quantities of these bodies do not fly through the system, but from the large number of ancient craters on the far side of the Moon it is obvious that they were three to four billion years ago. Conclusion: formally, everything converges.

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Gorkavy's hypothesis also had drawbacks: it is not very popular in the United States due to the fact that, as elsewhere, national scientific schools tend more toward "home-grown" scientific theories than to ideas from abroad.

In addition, the author was published in a Russian-language scientific journal, which further complicated the acquaintance of his concept with non-Russian speakers. Therefore, American researchers still adhere to the mega-impact theory, although they admit that the origin of lunar water in it is somewhat mysterious.

Japanese Observations: A Point in the Moon Debate?

The authors of the new work in Science Advances studied the data of the spectrometers of the Japanese artificial lunar satellite "Kaguya", which operated back in 2007-2009. They turned to the side of his observations that had not previously been introduced into scientific circulation, namely, to the registration of carbon ions by him. It turned out that, on average, 50 thousand of these ions per second fly out from one square centimeter of the lunar surface.

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This is quite a lot: according to calculations, more than the flow of the solar wind and the flow of micrometeoroids can supply to the Moon. In addition, over the basalt regions of the lunar seas, the flow of carbon ions is greater than over the regolith - and after all, basalt has poured out from the lunar mantle, that is, it cannot be rich in an element that was not originally on the moon.

All this means that carbon and other light elements inevitably had to be on the Moon from its very inception and cannot in any way be attributed to the "input" with comets and other bodies from the outer regions of the Solar System.

In theory, this closes the question. The large amount of carbon on the moon clearly indicates that it could not have been "dry" and devoid of light elements, as the mega-impact hypothesis claims. These data are also useful from a practical point of view: most likely, not only water, but also dry ice (solid CO2) will be found in lava tubes.

Oddly enough, in a number of cases it is a valuable resource from which methane can be obtained - a promising rocket fuel, the first rocket engine for which in 2019 was already tested in flight on the SpaceX experimental stand.

Until now, only water ice was known to exist on the Moon. In theory, it can also be decomposed into oxygen and hydrogen, and the latter is a good fuel. Alas, in practice, its application outside the Earth is problematic: hydrogen molecules are so small that even the best tanks in a vacuum in a few months of storage begin to lose it in large quantities.

Liquefied methane is much easier to keep in tanks: it can be stored there for years. Therefore, when using the Moon as a "refueling pad" on the way to Mars, it is potentially much more interesting to obtain methane from CO2 and water decomposition products than to extract lunar hydrogen from local water.

However, while this is a matter of perspective. It is not difficult to predict the immediate results of Kaguya's observations: now the supporters of the mega-impact theory will hastily seek some explanation and modify their hypothesis to explain how exactly the terrestrial rocks melted at the impact of the hypothetical Theia were able to hold light elements.

Scientists are inventive people, so we believe: they will succeed, the parameters of the mega-impact will be modified again and somehow adjusted to the newly found facts. Nevertheless, strategically speaking, their efforts to save the mega-impact theory are doomed.

The probability of such an event as a collision of two planets is a huge number of times lower than the probability of millions of asteroids falling to the ancient Earth. The first event is so difficult to realize that no one has yet provided even reasonable estimates of its probability. Asteroid bombardment - as it is easy to see from the relief of the same Moon and other satellites of our system - is more than usual. This means that this is a natural process, more consistent with Occam's razor.

From this it follows that the theory of multi-impact formation of the Moon will win, although it is possible that this will only happen after the current generation of mega-impact supporters retire.

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