The Earth is often called the "Blue Planet" not only because of the composition of the atmosphere, which gives the planet a delicate bluish tint, but also due to the oceans covering more than 70% earth's surface. It was in the oceans that life appeared, and therefore scientists are interested in the question of when and how water appeared on Earth.
Previously, it was believed that oceans formed on our planet when it was already quite “adult”, but latest research conducted at the Woods Hall Oceanographic Institution (USA) prove that there has always been water on Earth.
According to the previously existing theory, planets are formed dry, since their formation is associated with high-energy and impact processes. If there are water molecules on “young” planets, they evaporate until the planet completes the formation stage. Water reaches planetary bodies after their formation is completed, after the fall of comets and “wet” asteroids consisting of frozen water and gases. According to this theory, all the water that exists on Earth today came to the planet millions of years after its birth.
In their research, scientists from the Woods Hall Institute turned to carbonaceous chondrites, which are also a potential source planetary water. The simplest meteorites from this substance were formed in the flow of dust, ice and gases that gave birth to the Sun, long before the appearance of other topics of ours. star system.
According to Woods Hall employee Sune Nielsen, carbonaceous-chondrite meteorites are the most common objects in the solar system. They contain a fairly large number of water molecules and were previously considered the main source of water on our planet.
To find out when and how water appeared on Earth, scientists measured the ratio stable isotopes hydrogen, ordinary with one neutron and deuterium with two. IN various areas In our star system, this ratio differs. The researchers further concluded that comparing the proportion of carbonaceous chondrites in an object that formed at the same time as our planet could help answer the question of when and how water appeared on Earth.
The 4-Vesta asteroids were formed in the same area as the Earth and at the same time as it. They are covered by a basaltic layer of hardened lava. These celestial bodies are the oldest reservoirs of hydrogen in our system, as they appeared 14 million years after birth solar system. At this time, our planet was at the stage of its formation. Thanks to all these characteristics, 4-Vesta became ideal objects for determining how water appeared on Earth and when.
Having analyzed collected by NASA samples, scientists came to the conclusion: they have the same ratio of hydrogen and nitrogen isotopes as in carbonaceous chondrites and in the composition of the Earth. This makes them the most likely source of water molecules in the solar system. Consequently, water resources appeared on Earth simultaneously with solid rocks. Our planet was born in water.
During the research, scientists did not take into account the water that entered the planet later, since this was not necessary. On Earth in her “childhood years” there was already enough water resources for the birth of oceans. In combination with other conditions at the dawn of the formation of our planet, this led to the birth of life on Earth. Possibly on others too planetary bodies There was enough moisture for living things to emerge, but climate change later made them uninhabitable.
The water on this comet supposedly had the same isotopic composition as water on Earth. Scientists from SOHO, a joint project between NASA and the European space agency(ESA), calculated the approximate volume of water on the comet. The comet's explosion released a cloud of released hydrogen.
Comet LINEAR, which contained a large amount of water, exploded in August 2000, image Hubble telescope. Photo: NASA
“The idea that comets seeded life on Earth, bringing water and basic molecular composite particles"is a hotly debated subject, and this is the first time we've found a comet that could actually do this," says Michael Mumma of NASA's Goddart Flight Center.
Water has been found in other parts of space, but, unlike the water on this comet, its isotopic composition is different from that of Earth.
In 2011, astronomers discovered the largest and most distant accumulation of water in the Universe. It is 140 trillion times the amount of water in the world's oceans. It surrounded the quasar, the black supermassive hole, located 12 billion light years from Earth.
A quasar similar in type to APM 08279+5255, where scientists discovered a huge amount of water. Illustration: NASA/ESA
"The environment around this quasar is unique in that it produces large amounts of water," Matt Bradforle, a scientist at the lab, said in a NASA news release. jet propulsion NASA. “This is further evidence that water is distributed throughout the universe.”
In addition, in 2011, astronomers discovered oceans of water around the young star. This solar system, orbiting a star, is located 175 light years away. Large quantity water suggests that planets covered in water like Earth are common throughout the universe, NASA says.
An icy disk forming around a young star called TW Hydrae, located 175 light-years away in the constellation Hydra South. Illustration: NASA/JPL-Caltech
Since the human body is mostly composed of water, finding out the origin earth water will help to understand where the matter that makes up our bodies came from.
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Scientists are still arguing about the appearance of water on Earth. One friend started looking for hypotheses. I found six of them. There is no agreement in this world! Where does water on Earth come from - answer options.
Hypotheses about the origin of water on Earth
First hypothesis. Hot origin of the Earth
It is believed that the Earth was once molten fireball, which, radiating heat into space, gradually cooled down. The primordial crust appeared, chemical compounds of elements arose, and among them the compound of hydrogen and oxygen, or, more simply, water.
The space around the Earth became increasingly filled with gases that continuously erupted from cracks in the cooling crust. As the vapor cooled, it formed a cloud cover that tightly enveloped our planet. When the temperature in the gas envelope dropped so much that the moisture contained in the clouds turned into water, the first rains fell.
Millennium after millennium the rains fell. They became the source of water that gradually filled the oceanic depressions and formed the World Ocean.
Second hypothesis. Cold Origin of the Earth
The Earth was cold, and then it began to warm up. Warming up was the reason volcanic activity. Lava erupted by volcanoes carried water vapor to the surface of the planet. Some of the vapor, condensing, filled the oceanic depressions, and some formed the atmosphere. As has now been confirmed, main arena volcanic activity in the first stages of the Earth's evolution actually formed the bottom of modern oceans.
According to this hypothesis, the water was contained already in that primary matter, from which our Earth was formed. Confirmation of this possibility is the presence of water in meteorites falling to Earth. IN " heavenly stones» it is up to 0.5%. At first glance, a tiny amount. How unconvincing!
Third hypothesis
The third hypothesis again comes from the “cold” origin of the Earth with its subsequent heating.
At some stage of heating in the Earth's mantle at depths of 50-70 km, water vapor began to arise from hydrogen and oxygen ions. However high temperature the mantle did not allow it to enter into chemical compounds with the substance of the mantle.
Under the influence of gigantic pressure, steam was squeezed into the upper layers of the mantle, and then into the Earth’s crust. In the cortex there are more low temperatures stimulated chemical reactions between minerals and water, as a result of loosening the rocks, cracks and voids formed, which were immediately filled with free water. Under the influence of water pressure, the cracks split, turned into faults, and water rushed through them to the surface. This is how the primary oceans arose.
However, the activity of water in the Earth's crust did not end there. Hot water quite easily dissolved acids and alkalis. This “hellish mixture” corroded everything and everyone around, turning into a kind of brine, which gave sea water its inherent saltiness to this day.
Millennia replaced each other. The brine inexorably spread wider and deeper under the granite foundations of the continents. It was not given to him to penetrate into the granite itself. The porous structure of granite, like a thin filter, retained suspended matter. The “filter” became clogged, and when clogged, it began to play the role of a screen, blocking the path of water.
If all this took place, then under the continents at a depth of 12-20 km there are oceans of compressed water saturated with dissolved salts and metals. It is quite possible that such oceans spread under a multi-kilometer thick basalt bottom on earth's oceans.
This hypothesis is supported by sharp increase speed seismic waves at a depth of 15-20 km, i.e. exactly where the supposed interface between the granite and the brine surface should lie, the boundary sudden change physical and chemical properties substances.
This hypothesis is also confirmed by the so-called continental drift. The granite masses of the continents are moving. They “float”, although their speed of movement is only a few centimeters per century. Why not assume that the oceans of brines act as a kind of film under the “bottoms” of the continents, like a film of oil in a bearing between the axle and the shaft.
If brines exist, then in the future humanity will probably use them as the richest liquid ore in which the most valuable elements and their compounds are dissolved.
The fourth hypothesis of the English astrophysicist Hoyle
Its essence is this: the condensation of the protoplanetary cloud surrounding our proto-Sun proceeded unequally at different distances from the Sun. The farther from it, the lower the temperature of the cloud. Closer to the Sun, say, metals could condense as more refractory substances. And where the orbits of Uranus, Neptune and Pluto pass, according to Hoyle’s calculations, the temperature was approximately 350 K, which is already sufficient for the condensation of water vapor. 
It is this circumstance that can explain the “watery” nature of Uranus, Neptune and Pluto, formed in the process of merging particles of ice and snow. "Water" nature specified planets confirmed by the latest astronomical observations.
However, during the formation of the outer planets, there was a gravitational “pushing” of ice blocks into the region inner planets. Those of the blocks that were of sufficient size did not have time to completely evaporate from sun rays, reached the Earth and fell on it in the form of a kind of icy “rain”. Obviously, such “rains” were more abundant on Mars and very scarce on Venus.
Hoyle's calculations confirm the possibility of the formation of Earth's oceans from freezing rain, which took only a few million years.
Fifth hypothesis
She, like the fourth, assumes purely cosmic origin water, but from other sources. The fact is that a shower of electrically charged particles is continuously falling onto the Earth from the depths of space. And among these particles, a fair proportion are protons - the nuclei of hydrogen atoms. Penetrating the upper layers of the atmosphere, protons capture electrons and turn into hydrogen atoms, which immediately react with atmospheric oxygen. Water molecules are formed. The calculation showed that cosmic source this kind is capable of producing almost 1.5 tons of water per year, and this water reaches the earth's surface in the form of precipitation.
One and a half tons... By global standards - an insignificant amount. But it should be borne in mind that education is such space water began simultaneously with the emergence of the planet, i.e. more than 4 billion years ago.
Sixth hypothesis
As scientists have established, approximately 250 million years ago there was a single continent on Earth. Then, for unknown reasons, it cracked, and its parts began to creep apart, “floating” away from each other.
Evidence of the existence of a once united continent is not only the similarity coastlines, but also the similarity of flora and fauna, the similarity geological structures coasts. In short, few people now doubt the unity of the Earth's continents in the past. Another thing causes bewilderment: how can continental blocks, like giant “icebergs,” float away from each other if their roots go tens of kilometers deep? And what sets them in motion?
Research recent years confirmed: yes, the continents “float”, the distance between them is continuously increasing. The movement of continents is brilliantly explained by the expanding Earth hypothesis. The hypothesis states: initially the Earth had a radius half as large as it is now. The continents, then merged together, encircled the planet. Oceans did not exist. And then, at the border of the Proterozoic and Mesozoic (250-300 million years ago), the Earth began to expand. The single continent gave way to cracks, which, when filled with water, turned into oceans. And from then to our time, the radius of the Earth has doubled!
Invention atomic clock made it possible to determine with absolute accuracy the longitude and latitude of earthly objects from the starry sky. Measurements have shown that our planet... continues to expand!
Europe, for example, is expanding. Moscow and Leningrad are “swimming” east at a speed of 1 cm per year. And Hamburg, located in the center of Europe, remains in place.
Expansion speed European continent huge. After all, in just 20 million years (an insignificant period for geological epoch) as a result of such movement, a bowl of the future ocean 4000 km wide may form.
However, until now, proponents of the expanding Earth hypothesis did not have any arguments with which they could explain why the Earth is expanding.
Now there are such arguments.
Let us remember first of all (and we will return to this later) that the Universe consists of 98% hydrogen, i.e., the element that gives birth to water. Our Earth is 98% hydrogen. He came to us along with those cold particles cosmic dust, from which all the planets of the solar system were formed. And among these particles there were also metal atoms.
This is where we come across an interesting phenomenon. It turns out that metals are capable of absorbing huge amounts of hydrogen - tens, hundreds and even thousands of volumes per volume. Further: the more hydrogen a metal absorbs (or attaches), the denser it becomes, i.e., it decreases more and more in volume. Yes, we didn’t make a reservation - it’s decreasing. So, alkali metals, adding hydrogen, decrease in volume by 1.5 times already at atmospheric pressure. As for other metals (for example, iron and nickel, of which, according to scientists, the Earth’s core is composed), then at normal atmospheric pressure (105 Pa) the decrease in volume is very insignificant.
However, as the dust cloud thickened, it gravitational compression, and the pressure inside the proto-Earth increased. Accordingly, the degree of hydrogen absorption by metals of the iron group also increased. Compression generated the antipode of pressure - heating.
And since the central regions of the formed planet were subjected to the greatest compression, the temperature there also increased more rapidly.
And at some stage of heating, when the temperature in the Earth’s core reached a certain critical value(transition of quantitative growth to a new qualitative state!), the reverse process began - the release of hydrogen from metals.
The disintegration of metal-hydrogen compounds, i.e., the restoration of metal structures, caused a sharp increase in the volume of matter in the Earth's core. The expansion of the metal core manifested itself with such force that the mantle and crust of the planet, unable to withstand it, cracked.
Thus, the degassing of hydrogen was accompanied by the expansion of the Earth. Meanwhile, hydrogen, penetrating the enormous thickness of the planet, captured oxygen atoms along the way, and water vapor was already escaping to its surface. Condensing, the water filled the cracks in the crust. Oceans gradually formed.
So, six hypotheses of the origin of earthly water. Over time, it will become clear which of them is true. Perhaps all six will turn out to be true, each to some extent. In the meantime, the question “Where did water come from on Earth?” remains open.
There are several fundamentally different assumptions that have divided scientific minds into two camps: some are supporters of the meteorite or “cold” origin of the earth, while others, on the contrary, prove the “hot” origin of the planet. The first believe that the Earth was originally a large, solid, cold meteorite, while the second argue that the planet was hot and extremely dry. The only undeniable fact is that such a vital important element, like water, appeared on Earth at the stage of formation of the blue planet, that is, long before.
The hypothesis of a “cold” origin of the planet
According to the cold origin hypothesis globe at the beginning of its existence it was cold. Subsequently, due to the decay, the planet's interior began to warm up, which became the cause of volcanic activity. The erupted lava brought various gases and water vapor to the surface. Subsequently, with the gradual cooling of the atmosphere, some of the water vapor condensed, which led to a huge amount of precipitation. Continuous rains for thousands of years initial stage the formation of the planet became a source of water that filled the oceanic depressions and formed the World Ocean.
The hypothesis of a “hot” origin of the planet
Most scientists who hypothesize the “hot” origin of the Earth do not in any way connect the appearance of water on the planet with. Scientists have suggested that the structure of planet Earth initially contained hydrogen layers, which later entered into chemical reaction with oxygen present in the earth's mantle at the initial stage of formation. The result of this interaction was the emergence huge amount water on the planet.
However, some scientists do not exclude the participation of asteroids and comets in the creation of water space on huge territory land. They suggest that it was thanks to the continuous attacks from large comets and asteroids, which carried reserves of water in the form of liquid, ice and steam, that huge expanses of water appeared, filling most of planet Earth.
At all times, people have wanted to know how planet Earth was formed. Despite the fact that there are many hypotheses, the question of the origin of water on our planet still remains open.
When the Earth began, it was too hot for water. But where did she come from then? Two new studies reveal how Jupiter played a role.
Humanity exists because there was a real explosion. And more than once. During the birth of the Solar System, small pieces first emerged from dust particles, and then large asteroids. Massive bodies constantly merged with each other and melted into a new body. In the end, only a few planetary fragments remained, which gradually cleared their way around the sun. This is how the Earth came into being 4.5 billion years ago.
This theory of the origin of the Earth represents a scientific compromise. But he doesn’t answer all the questions. Where did water come from on the blue planet? After all, researchers agree that when the Earth formed, it was too hot for water molecules. There are several theories about its origin.
Two current studies advance one of the the latest theories, according to which Jupiter played one of the leading roles. Water and others liquid substances were brought to Earth differently than previously thought, for more late stage with the help of comets and asteroids, and already at the first stage of the emergence of the planet.
At first it was hot
When the space bombardment occurred, the temperature inside the solar system was so high that water existed only in gas form. But young, unformed planets could not accept this gas. Instead strong solar wind carried him into the depths outer space. Only later is vital chemical compound H20 returned from the cold outer solar system. When? And how?
A study by scientists Mario Fischer-Gödde and Thorsten Kleine from the University of Münster indicates that the strange movement of the planet Jupiter during the first million years of the solar system carried water back to Earth. These data contradict the widespread theory, according to which water appeared on Earth only during the last phase of the formation of the Earth 4.4-3.9 billion years ago with the help of meteorites and asteroids. Their main argument — rare element Ruthenium.
The material special properties. It gravitates towards iron, siderophilic, as the researchers say, and therefore, at the initial stage of the planet's emergence, it mostly sank to the core, which contains iron. But ruthenium is also found in the layers of the Earth’s crust and mantle. Ideal for Fischer-Gedde and Kleine, because this way they know what to talk about recent history Earth.
Wandering Jupiter
Terrestrial ruthenium has a specific composition. It consists of atoms with different number neutrons, isotopes, and thus possesses a kind of chemical fingerprint that the team could compare to ruthenium from young meteorites.
Depending on the origin of meteorites, which are remnants of the young Solar System, the composition of their ruthenium also differs. Comets containing water from the outer Solar System have a different fingerprint than dry meteorites from the inner Solar System. The origin of the mantle from the last stage of the formation of the Earth can be explained by this.
The results of the Fischer-Goedde study indicate that the mantle comes from meteorites from the enstatite chondrite family. Water-rich objects from the outer solar system do not appear to have collapsed.
“Since we can rule out that water arrived on Earth with meteorites, it happened before then,” says Thorsten Kleine. His research substantiates the “Great U-turn” model that was established only a few years ago.
According to this model, young Jupiter drifted toward the inner solar system due to the effect of the planet's gas envelope. When Saturn later emerged, it was pulled outward again into its present orbit. While gas giant On its way back, it pushed rocky material towards the Sun, it threw meteorites and water from the outer solar system towards the Earth. "Thus, in certain time“A lot of water-containing meteors hit Earth,” Kleine says. And this happened sooner early stage history of the Earth.
Anhydrous meteorites formed the Earth
The researchers were supported in their theory by another study by Nicholas Daufas from the University of Chicago. The American researcher also turned to the idea of ruthenium and applied it simultaneously to several elements. All of them appear both on Earth and in meteorites. Unlike German scientists, he did not test his assumptions on real cosmic elements, but developed them based on existing research mathematical model about the origin of earthly material. According to it, the Earth arose in two phases. In the first stage, the building material was formed by some water-rich meteorites from the outer solar system - about one-tenth of the Earth's then mass - and water-free enstatite chondrites. In the second stage, there were no more water-rich meteorites; only enstatite chondrites were heading towards the Earth.
No data on comets
The problem is that all scientists have studied only meteorites, that is, celestial bodies that fell to Earth. “We hypothesize that the ratio of ruthenium isotopes becomes less consistent with that of Earth the farther away from the sun comets occur,” Kleine says. “Thereby we exclude external celestial bodies as carriers of water at the last stage of the emergence of the Earth.” If, contrary to expectations, there are comets outside the solar system that have the same ruthenium isotopes as Earth, this model will no longer work.
What is missing to solve the mystery of the source of the earth's water is reliable data on such celestial bodies. They can be provided from expeditions to comets. Because Rosetta mission The European Space Agency has not yet provided sufficient quantity data, researchers are betting on future projects. However, an official decision on such a mission has not yet been made.
