1. Where does so much water come from on Earth?
According to scientific concepts, the Earth, after its formation 4.5 billion years ago, was a rocky desert. Where did so much water come from? Some scientists speculate that water may have entered the Earth during a heavy meteorite bombardment that happened 4 billion years ago. At that time, several large ice asteroids or comets crashed into our planet, which laid the foundation for the earth's hydrosphere. Unfortunately, too much time separates us from that era to find weighty confirmation of this assumption.
2. What is the core of the Earth?
In the 1940s, scientists were confident that they had completely figured out the structure of the earth's interior. Comparing the composition of the crust with that of meteorites, the researchers drew attention to the relative deficiency of iron and nickel in the planet's lithosphere. Based on this, scientists have come to the conclusion that these elements are concentrated in the earth's core. However, gravimetric measurements from the 1950s showed that such assumptions were inconsistent. The kernel turned out to be too light. Today geophysicists continue to wonder what is in the very center of the planet. They are also deeply puzzled by the periodic "flips" of the Earth's magnetic field, caused by the flow of molten iron in the outer core of the planet.
3. Where did the moon come from?
The popular version of the appearance of the moon is the collision of the Earth with another planet. Scientists have not yet come to a consensus on this issue, since some facts "do not fit" into the framework of the proposed theories. For example, the chemical composition of the stone shells of both planets is so close, as if the entire Moon was once part of the Earth.
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4. How did life appear on Earth?
Did life originate on Earth, or was it brought to the young planet by meteorites? The "bricks" of life, such as amino acids, were found on small cosmic bodies, which supported the panspermia hypothesis. However, until now, biologists cannot describe in detail how these elements were able to combine into the first living organism. We also do not have the remains of the first microbes, which, most likely, fed on rock.
5. Where did all the oxygen come from?
We owe our existence to cyanobacteria - microscopic creatures that radically changed the Earth's atmosphere. About 2.4 billion years ago, they enriched the planet's gas envelope with oxygen. However, over the next three billion years, the oxygen content in the atmosphere fluctuated wildly until it stabilized around 541 million years ago. Was it only bacteria that worked on the composition of the atmosphere, or was it influenced by something else? Elucidation of the reasons for the emergence of an oxygen atmosphere is important for understanding the evolution of the earth's biosphere.
6. What caused the Cambrian explosion?
The emergence of complex life forms in the Cambrian, four billion years after the formation of the Earth, is a unique moment in the history of the planet. Almost suddenly at this time, animals appear with brains and blood vessels, eyes and hearts. Life is developing faster than in any other era. Some theories explain the Cambrian explosion by a jump in the oxygen content in the atmosphere, but there are other assumptions, in particular, the acceleration of evolution due to the "arms race" among predators and prey.
7. How did tectonic processes begin?
Geologists still do not know when the "engine" of tectonic processes started working. Traces of ancient geological activity have long been erased from the face of the earth. The only rare minerals, zircons, are remnants of the primary continental rock that existed on Earth 4.4 billion years ago.
8. Can we predict earthquakes?
The existing earthquake forecasting methods, at best, call the probability of a cataclysm in a certain time interval. The largest attempt at predicting an earthquake (Parkfield, California) gave an error of 12 years. The main problem that prevents making accurate forecasts is the lack of understanding of the factors that provoke the beginning and end of earthquakes.
Based on materials from Livescience
ALEX KUDRIN