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A biosphere based on ammonia would likely exist at temperatures or air pressures that are extremely unusual in relation to life on Earth. Life on Earth usually exists between the melting point and boiling point of water, at a pressure designated as normal pressure, between 0 and 100 °C (273 and 373 K). When also held to normal pressure ...
Silicon is one of the most abundant elements on Earth, and is considered necessary for life. [ 2 ] [ 3 ] The silica cycle has significant overlap with the carbon cycle (see carbonate–silicate cycle ) and plays an important role in the sequestration of carbon through continental weathering , biogenic export and burial as oozes on geologic ...
The Earth's crust is one "reservoir" for measurements of abundance. A reservoir is any large body to be studied as unit, like the ocean, atmosphere, mantle or crust. Different reservoirs may have different relative amounts of each element due to different chemical or mechanical processes involved in the creation of the reservoir.
More than 90% of the Earth's crust is composed of silicate minerals, making silicon the second most abundant element in the Earth's crust (about 28% by mass), after oxygen. Most silicon is used commercially without being separated, often with very little processing of the natural minerals.
In most silicate minerals, silicon is tetrahedral, being surrounded by four oxides. The coordination number of the oxides is variable except when it bridges two silicon centers, in which case the oxide has a coordination number of two. Some silicon centers may be replaced by atoms of other elements, still bound to the four corner oxygen corners.
The carbon cycle is a biogeochemical cycle that is important in maintaining life on Earth over a long time span. The cycle includes carbon sequestration and carbon sinks. [4] [5] Plate tectonics are needed for life over a long time span, and carbon-based life is important in the plate tectonics process. [6]
The abundance of the chemical elements is a measure of the occurrences of the chemical elements relative to all other elements in a given environment. Abundance is measured in one of three ways: by mass fraction (in commercial contexts often called weight fraction), by mole fraction (fraction of atoms by numerical count, or sometimes fraction of molecules in gases), or by volume fraction.
Silicon is one of the most abundant elements on earth, and in 1959 no one was working on its metabolism. The biology of silicon had been shunned by all biochemists, the dogma being that it was inert. Volcani realized that diatoms, whose life cycle is based on silicon, provided an ideal experimental canvas.