Where does the water on Earth come from?

The most representative theories on the origin of water on the earth are the "exogenous source theory" and the "self-source theory".

1. The "exogenous source theory" believes that the water on the earth comes from outside the earth. One candidate for an alien source of water is comets and water-rich asteroids.

1. If water was indeed brought to the earth by comets or asteroids, then the time when it came to the earth was not during the formation of the earth, but after the earth evolved to form the crust and mantle. period. But it does not rule out another situation, that is, water was actually a component of interstellar dust in the beginning, and the earth is composed of interstellar dust.

2. The solar wind reaches the upper layer of the Earth’s atmosphere, bringing a large number of hydrogen nuclei, carbon nuclei, oxygen nuclei and other atomic nuclei. These nuclei combine with electrons in the Earth’s atmosphere to form hydrogen atoms, carbon atoms, and oxygen atoms. Wait, and then turn into water molecules through different chemical reactions. It is estimated that almost 1.5 tons of this "cosmic water" is produced in the upper atmosphere of the Earth every year. This water then falls to the earth in the form of rain and snow.

2. The "self-origin theory" believes that the water on the earth comes from the earth itself.

In the early stages of the formation of the Earth, its interior contained very abundant hydrogen elements, which later reacted with oxygen in the mantle and eventually formed water. Extended information

Softness and hardness

Water in daily life can be divided into soft water and hard water. Water with more soluble calcium, magnesium and iron salts is called hard water. The total concentration of Ca2+, Mg2+ and other ions contained in water is called hardness. The unit of water hardness is mol·m-3 or mmol·dm-3.

Changes in water density

The density of water is maximum at 3.982°C, which is 1000kg/m3. When the temperature is higher than 3.982°C (it can also be ignored as 4°C), the density of water It decreases with the increase of temperature. At 0~3.984℃, water shrinks when heated and expands when cooled, and the density increases with the increase of temperature.

Properties of water:

Three-state changes

As we all know, water has three states: solid, liquid, and gaseous.

But water has more than three states: supercritical fluid, supersolid, superfluid, fermion condensate, plasma,

Bose-Einstein condensate Status and so on.

Physics

Usually a colorless, odorless liquid.

Reference: People's Daily Online - Where does the water on the earth come from