According to one of the most popular models of the Moon's formation, a natural satellite of our planet could appear as a result of a collision of some cosmic body with the Earth more than 4.5 billion years ago. This body was Teiya, a protoplanetary object, with the “embryo” of the Earth. The collision led to the ejection of the matter of Teiya and the proto-Earth into space, and from this matter the Moon was formed, which explains its surprising geological and chemical similarity to our planet. In the framework of the new study, scientists tried to understand in more detail what was the fate of our satellite after this event.
During the period of katarcheya (geological aeon), the Moon looked completely different from what it looks like today. It was more like a red-hot lava that possesses an exotic superdense atmosphere of silicon and metal vapors. And it was 10 times closer to the Earth's surface than it is today.
In the course of the study, a group of scientists concluded that one of the features of the Moon may indicate that the Earth was deprived of oceans from liquid water during the first 400 -500 million years of existence. And such conclusions, in turn, impose serious limitations on the time of the origin of life on Earth. About their work, scientists shared in the journal Geophysical Research Letters.
As it is commonly believed, in the next few million years after its formation, the Moon quickly removed from the Earth as a result of tidal forces until eventually it reached the orbit on which she is today. Later, when the Moon began to always look at the Earth with only one side, this process slowed down sharply, and now it moves away from our planet at a rate of about 2-4 centimeters per year.
Zhong and his colleagues uncovered one unusual detail of this process, drawing attention to the most mysterious feature of the Moon – its unusual “hump”, located on the equator. This structure was discovered by the French astronomer Pierre Laplace two centuries ago. Laplace noted that the Moon is “flattened” about 17-20 times stronger than it should be, given the speed of its rotation around its axis.
“The lunar equatorial” hump “can contain the secrets of the early history of the evolution of the Earth, of which we even did not know, “says researcher Shijie Zhong from the University of Colorado in Boulder, USA.
The researchers believe that the existence of this structure indicates that in the distant past, the Moon revolved much faster than today. American planetary scientists tried to understand how quickly the Moon “braked” by studying how this “hump” was constructed and trying to reproduce its appearance with the help of a computer model of the development of the solar system.
These observations unexpectedly showed that the generally accepted theories about the rapid deceleration of the Moon in the early years of its existence were erroneous – the speed of rotation of the satellite of the Earth remained high for at least the first 400 million years of its existence. Otherwise, the Moon would always remain a “liquid” planet or have a completely different shape and dimensions than today.
A similar scenario, as Zhong explains, is possible only if the Earth was not at that time covered by the ocean from the water, comparable in size with the current hydrosphere of the planet. This means that there was no water in the liquid form on the young Earth. It either was absent on it in principle, or was brought in after the formation of the “hump” of the Moon, or was on it in solid form, that is, in the form of ice.
“The hydrosphere of the Earth, if it existed at that time, was completely frozen, as a result of which tidal forces practically did not “brake” the Moon. The likely reason for this, we believe, may be that the Sun shone then is not as bright as it is today, “says Zhong.
Such conclusions put serious restrictions on the time of the appearance of life on Earth and force scientists to doubt the recent statements of geologists that the first living organisms could have appeared on our planet already 4 billion years ago.