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When we see a cloudy day, morning dew, rain, snow, lakes, rivers, or the ocean, we know that water is everywhere. Water also hides in magma-filled depths, in meteorites or comets, or in the cells of living things. Makes chemical reactions possible. Invisible to our eyes, this tiny molecule of two hydrogens and one oxygen has shaped our planet.
Alberto Vitale Brovarone in American mineralogist together with renowned geologists, astronomers, astrobiologists have provided information on this fundamental role of water in the history of our planet. Their article reviews recent research on two important types of chemical reactions involving water and their role in shaping the planet: hydration reactions that add water to molecules and dehydration reactions that remove water from molecules.
Here is a video explaining how minerals “hydrate”. Source: Youtube
Ever since the formation of our planet within a cloud of gas and dust that would become our solar system, it is highly likely that the mineral particles that make up the forming Earth could hold water on its surface. Some of these important minerals are known as silicates. Silicates are a type of rock material that was likely available on early Earth billions of years ago to make water react. This reaction is called hydration because water is trapped by the crystal structure of the mineral when it forms. When water is added to a mineral, it creates a new mineral called a hydrate or hydrated mineral. In the case of olivine, its hydrated mineral is called serpentine. Serpentine is a mineral that holds up to 13% water!
Beyond our solar system, comets or asteroids rich in hydrogen and carbon have landed on Earth and reacted with water. The carbon and hydrogen on these space rocks reacted with water to produce organic compounds – the first very important molecules for the origin of life. They also contained silicates and ice, which reacted by forming coils or clays like smectite. The water bound to the silicates enriched the solid Earth and the rest was released as water vapor to form the oceans and atmosphere.
If the ocean were the size of an Olympic-sized swimming pool, the amount of water trapped on the ocean floor each year would be the size of a lentil. In other words, one trillionth of the ocean’s volume is trapped in the earth’s solid crust each year. This water entrapment also occurs with CO capture2 and resists silicates, transforming them into hydrated minerals such as serpentine, brucite, amphibole, smectite, chlorite and epidote.
Through areas where tectonic plates come together, called subduction zones, the ocean floor is buried and carried in the mantle. The water released in the dehydration of the minerals enriched the coat. As the mantle rose, it formed granite, a low-density mineral that was no longer recycled in the depths of the Earth. This has stabilized the continents. However, the authors point out that not all water is returned to the earth’s surface by dehydration and the formation of granite. Much of it is also present in small quantities in anhydrous minerals which contain very little water. Surprisingly, even diamond found deep inside the Earth, between 525 and 660 km, contains inclusions of a mineral known as ringwoodite which contains up to 1.4% water.
The expression “The Earth is alive” is widely used by both terrestrial and planetary geologists. Water makes life possible, including the functioning of our own planet.
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