Stellar Evolution and Terrestrial Metabolism: Four Elements of Planetary Life Systems
of hydrogen into helium in the nucleus and causing the star to enter the Main Sequence, the other remaining part, not mature for this evolution, remains as a protoplanetary disk and will constitute the germ of what will be the development of a planet with its evolution. After the separation and expulsion of elements that hindered their formation, the star will enter the Main Sequence and remain there, providing the Planetary System it hosts with the opportunity for its evolution. After the time spent by the Star in the Main Sequence, it proceeds in its evolutionary path by reincorporating the elements it had previously expelled to operate its transmutation, reabsorbing and transmuting them. The separation of elements most refractory to a certain evolutionary principle and their subsequent reabsorption in a second phase is a typical element of organic evolution. Part of the system must separate and achieve the objective set by the organic system to then extend it to others only in a second time. Thus the star separates from the refractory elements, to then reincorporate them successively in a second phase of its evolution, transforming them.
Figure 16: Tectonic activity is essential for planetary thermoregulation, but is also fundamental for keeping minerals and elements necessary for life in circulation. On the continental crust, interfacing with the atmosphere, rock silicates react with carbon dioxide, producing silicic acid $H_4SiO_4$ and calcium/magnesium bicarbonate. Transported to the ocean by rainwater, these form silica ($SiO_2$) and carbonate, which accumulate on the ocean floor. Living organisms that produce skeletal structures rich in silica or carbonate improve the process. In subduction areas, silica and carbonates are reconverted into silicates and carbon dioxide, which return to the surface through volcanic emanations and tectonic elevations.
Figure 17: On the right, a representation of Earth's magnetic field in a normal phase. On the left, a time scale in millions of years, the black zones indicate periods of time when polarity was equal to current polarity, while the light zones indicate periods of time with inverted magnetic polarity.
The Four Elements in Terrestrial Metabolism
The terrestrial environment in which we live is formed by the synergistic and coordinated action of four fundamental elements to create the ecological conditions necessary for life:
- The Earth's Core (Fire);
- The Atmosphere (Air);
- The Hydrosphere formed by the oceans (Water);
- The Continental Crust (Earth).
In the absence of coordinated action of these four elements, or their imbalance, the ecological conditions necessary for life as we know it would not be possible, as in the case, for example, of the Moon or Mars. Earth in its interior is formed by a solid inner Core, which probably reaches 6000°C, surrounded by a liquid Core that today has an estimated temperature of about 4000°C. The interaction between the solid Core and the liquid one generates, through powerful convective motions, a powerful magnetic field (Fig. 17) that protects Earth from solar wind, an intense flow of charged particles (mainly electrons, protons, and helium nuclei) emitted from the Sun's surface. In the absence of such protective magnetic field, Earth's atmosphere would probably be progressively stripped from our planet, which would quickly find itself without it.
The atmosphere in turn is fundamental for maintaining the oceans. In the absence of atmosphere, the water present on Earth would be frozen along the entire surface of the planet or evaporated. In Earth's atmosphere there are molecules consisting of three or more atoms such as water vapor ($H_2O$), carbon dioxide ($CO_2$), methane ($CH_4$) and ozone ($O_3$). This configuration allows molecules to absorb infrared radiation and emit at a slightly longer wavelength. The result is that much of the heat emitted by the solid surface and oceans remains in the atmosphere, which behaves like a blanket covering the planet and keeping it warm during the night.
The oceans, on the other hand, are fundamental for plate tectonics. The areas of active mantle upwelling in today's Earth are usually found on the ocean floor. When mantle material rises toward the surface, it melts due to lower pressure and emerges at the surface as lava. The emitted lava builds new oceanic crust on both sides of oceanic ridges, while pre-existing crust moves away. The spreading velocity varies from 10mm per year up to 160mm.