History of the Earth in English PakWap

 [][] Some astronomers think our satellite was created side by side with Earth. The idea is that both were formed at about the same time, from the same gas and dust, and at the same part of our solar system’s protoplanetary disk. 

Real History of the Earth

The theory is called Co-formation and it fits because of the isotopic similarities between the two space objects. But at the same time, it cannot explain the difference in the size of their iron cores. [] The leading and, perhaps, the most mind-blowing theory is that the Moon was born as a result of a Giant impact with a different celestial body.

 There’s a chance that Earth wasn’t the only planet that was forming million kilometers [ million miles] from the Sun. Earth’s creation may have been accompanied by another planet dubbed Theia. This strange world must have been smaller than our planet, just about the size and mass of Mars. At first, it could have a stable orbit, but as Earth increased its mass by gathering more material, 

Theia’s orbit was destabilized. And so it swung back and forth toward our planet until, eventually, the two protoplanets collided. The speed of collision was low, so the Earth wasn’t destroyed. However, the impact must have created a disk of debris of molten rock and hot gas that became 

the building blocks of the Moon. Both Theia and the Earth could be composed of a combination of materials, and more of the lower density splatter would eventually transform into the Moon. If this is the case, it explains why our planet has a higher density and thicker core than our satellite, 

and why the Earth and the Moon spin the way they do around each other. [][][][] But let’s get back to Earth. Throughout the next half a billion years [Hadean Eon . – . billion years ago], the Earth resembled a ball of a molten surface, volcanism, and asteroid impacts. And several things made it

Brief History of the Earth

 extremely hot gravitational compression, radioactive decay, and asteroid impacts. A big amount of this initial heat is still there, deep inside our planet. But as it cooled, minerals started to crystallize, and because of the different densities of materials, the crust, mantle, and core were formed.

 [] So how did water appear on a hot rock floating through space? +[Origin of water] Oceans cover more than % of the Earth’s surface. This is . billion cubic kilometers [ million cubic miles] of surface water or ice.

 [][] But the fact that there’s more liquid water on our planet than on any other known rocky world in our solar system isn’t fully understood. And as with the Earth and the Moon, there are several hypotheses as to how water appeared here. One likely reason is extraplanetary sources, such as comets, trans-Neptunian objects, or even protoplanets. There’s actually a lot of water in our solar system. 

⅔ of Uranus and Neptune, for example, are made of ice. [] So if our planet was born hot and dry, then water must have come from somewhere else – brought by icy comets and asteroids. Comets are made of dust and ice, with most of that ice being frozen water. So they might be the clue.

Extra History of the Earth

 But measurements show that comet water has a lot more deuterium in it compared to that found on Earth. What about asteroids? Because their ratio of deuterium to normal hydrogen water is closer to that we have on our planet, they are even a better candidate. 

Also, asteroids are % water, but due to their small size, there must have been a colossal number of impacts to explain all the water on our planet. To fill the planet with , million cubic kilometers of water might seem like a lot. To compare, this much water would have been enough to cover the contiguous United States to a depth of roughly kilometers [ miles].

 But this still isn’t a lot. In fact, water amounts to only about .% of our planet’s mass. And since Earth experienced periods of heavy bombardment in the past, this is actually a possible scenario. [][][][] ???Researchers also think that when our planet formed, huge amounts of hydrogen were captured in its rocks and minerals. And because of the mantle’s heat,

 hydrogen and oxygen-rich minerals started to melt. This made it possible for water to spew from the Earth’s crust. According to scientists’ estimates, about oceans of water could exist within the mantle up to this date. [] Probably

 the most astonishing of all is the volcanic outgassing hypothesis. According to this idea, water may have come from volcanism. In other words, it was always there in the form of minerals with oxygen and hydrogen, hidden beneath the crust of our planet. And volcanoes only helped it break free as vapor. It originated in volcanic eruptions, then condensed and fell as rain. 

Scientists think that all volcanic eruptions contain some water vapor, and that it may have been enough to account for the Earth’s surface water. [][] This still remains an open question, but whatever the case, with water, there often comes life. +[First life] Life, most likely, began during the late Hadean or early Archean Eon that lasted from .-. billion years ago. 

There’s evidence of life in at least .-billion-year-old rocks from Akilia Island, Greenland, and the oldest form of life discovered by scientists are tiny hematite tubes estimated to be . billion years old! [][][][] Hypotheses include a chemical origin of life in the early atmosphere, hydrothermal vents,

 deep seas, oceans, and even comets that came here from somewhere in space. [] It’s highly possible that life began from the chemical environment of the early atmosphere and oceans. But they were nothing like what we have today. The atmosphere was oxygen-free but was abundant in methane, carbon dioxide, sulfur, and nitrogen compounds. And some space objects in our solar system are known to have an atmosphere like this. In one experiment,