How and when did water appear on Earth? Scientists are still debating on this topic, however, no one has yet given an accurate and logically proven answer. To date, there are several suggestions of how liquid could have formed on the planet. Among them there are both completely absurd and reasonably logical hypotheses, but so far none of them is completely reliable.
How did water appear on Earth? Briefly about the main hypotheses
Water plays a large role in maintaining life on the planet, because it is the main internal environment of any organism. Without water, a person can survive on average no more than three days, and the loss of 15-20% of the fluid often leads to death.
How did water appear on Earth? The hypothesis of the formation of this substance is not numerous, and also none of them has yet received true evidence. Nevertheless, only they can somehow explain the formation of the hydrosphere of our planet.
Space origin hypothesis
A team of researchers suggested that water appeared along with numerous falling meteorites. This happened about 4.4 billion years ago, when the planet was still in its infancy, and its surface was a dry, devastated earth, over which an atmosphere had not yet formed.
When asked how water appeared on Earth, adherents of this hypothesis answer that the first molecules of this liquid brought meteorites with them. At first, these molecules existed in the form of gas and accumulated, and later, when the planet began to cool, the water went into a liquid state and formed the Earth’s hydrosphere.
It is possible that the chemical formation of water came from primary protons of hydrogen and oxygen anions, but the likelihood of such a reaction in the thickness of celestial bodies, which subsequently fell to Earth, is catastrophically small.
Another hypothesis of how water appeared on Earth
It was proposed by a group of researchers led by the famous scientist V.S. Safronov. The essence of his assumption is the terrestrial origin of the water that formed in the bowels of the planet.
Under the influence of numerous meteorite falls, our hot planet at that time began to form a large number of volcanoes from which magma burst. Together with it, “water vapor” stood out on the surface, which caused the formation of the Earth’s hydrosphere.
Despite the fact that the theory laid the basis for the terrestrial origin of water, it cannot answer many questions. For example, how did rocks in the lithosphere melt so much to cause the formation of many volcanoes? And how did water vapor form? At first, scientists suggested that at that time there was groundwater that, through the vents of volcanoes, along with magma broke out in a gaseous state.
This theory of steam formation was refuted by P. Perro, a 17th-century naturalist. He proved that groundwater was formed due to precipitation, and this requires the presence of the atmosphere. 4.4 billion years ago, the atmosphere did not exist.
And the last theory
So how did water appear on Earth? Another hypothesis was able to approach on the other hand the question of the formation of the hydrosphere of the planet. Like the past assumption of V.S. Safronov and his coauthors, this hypothesis is repelled by the terrestrial origin of water.
The difference is that, according to researchers, water molecules formed together with the protoplanetary disk of the Earth, i.e. at the time of the formation of the planet itself. The source of water molecules was deuterium and oxygen.
Deuterium is ordinary hydrogen with one neutron in the nucleus. This heavy isotope was found in samples of ancient basalts found in the Arctic on Baffin Island (1985). These rocks are formed from protoplanetary dust particles that were not exposed during planet formation. According to the researchers, the chemical nature of deuterium would not allow an isotope to form outside the planet.
This is how water appeared on Earth according to these scientists. If their data are correct, about 20% of the modern world ocean formed during the formation of the protoplanetary disk. Today, researchers are looking for a way to prove that most of the world's oceans, as well as atmospheric water vapor and groundwater, have formed from "protoplanetary" water.