Lost among the trillions of trillions of galaxies in the sheer power of the universe, the fragile Earth in the Milky Way is as conspicuous as a single water molecule in all the water found on our planet, probably eliminating the possibility that humans be the supreme intelligent race ever.
Earth is teeming with carbon-based life, built with various proteins and the wonderful self-replicating compound DNA, and works with water as a potential solvent and oxygen as an electron acceptor for the plethora of red ox metabolic reactions that are taking place. cape. . Other possible biochemistry of extraterrestrial life have often been disparaged and scientist Carl Sagan calls this fallible discrimination carbon chauvinism, implying that we have been quite narrow in imagining the prospects for radically different life forms in other parts of the universe. Victor astrophysicist. J. Stenger proposes a concept of molecular chauvinism discarding the need for molecular combinations and visualizes life in other parallel universes in which atomic nuclei and other chemical structures could differ drastically. Stephen Hawking also accepts that aliens could prevail without carbon-based structures and DNA. The popular lore of science fiction, in the realm of extraterrestrial life, has witnessed various notions such as life on a planet with oceans of sulfuric acid, creatures that inhale pure cyanide, and life that thrives in a chlorine atmosphere. Several biochemical occurrences suitable for life on extremely different planets on Earth have been hypothetically proposed.
Silicon, a component of the carbon family, resembles carbon in several aspects of its chemical properties. However, it would be hateful to think of silicon-based life in planetary conditions similar to those on Earth. Silicon dioxide, the silicon counterpart of carbon dioxide, which is formed after respiration in an oxygen atmosphere, would clog the lungs with sand particles that constitute it. This sand would melt at high temperatures and the existence of a silicon-based life that breathes oxygen could be possible on planets with several thousand degrees of temperature or excessive pressure. Silicon in life is said to exist as silicone polymers. In a sulfuric acid environment, silicone polymers may be more stable than hydrocarbons. But the instability of long-chain complex silicones shakes this perception slightly The greatest abundance of carbon to silicon in the entire cosmos, the versatility of carbon in the formation of compounds, the presence of a carbon-based life on Earth despite from the availability of larger amounts of silicon, meteorites containing carbon particles showing no signs of silicone polymers; the silicon theory of life is apparently susceptible to such facts. Still, silicon-based life structures thrive even on Earth. Biogenic silica forms the skeletal structure of several species of microbes, including diatoms (algae) and radialoria (protozoa). Even the earliest organisms on Earth are supposed to have silicate structures. If silicon-based life existed, the role of silicon would be more likely to be less analogous to that of carbon. For example, silicon would form the structural component, while carbon would be functional in metabolic aspects.
Since prehistoric times, water has been considered very rudimentary for the existence and survival of life and this is valid for planets similar to Earth. A new perspective now supports the existence of life at temperatures as low as -100 ° C. Ammonia has been considered analogous to water, showing several similarities. But ammonia is not suitable for aerobic life by inhaling oxygen, since ammonia is flammable in oxygen. Like water, ammonia can accept or donate a proton. The acceptance of protons forms an ammonium cation analogous to the hydronium ion of water and the donation of a proton gives an amide ion analogous to the hydroxide ion. The rather useful carbonyl group (C = O) becomes unstable in ammonia solution and an effective replacement for this would be the imine group (C = N). Ammonia could even establish an acid-base balance in organisms and act as a buffer similar to water. But the weaker hydrogen bonds in ammonia and its consequent tendency to vaporize at low temperatures pose critical problems for survival with ammonia. However, on planets and moons at fairly low temperatures, in conjunction with liquid ammonia, various other compounds available in a condensed state could be used. At elevated pressures, the melting and boiling points increase dramatically (196 K and 371 K at 60 atm pressure, respectively). Hydrogen fluoride could also serve as a potential alternative to water. Hydrogen bonds and strong polarity make it an appropriate support for life.
It has been suggested that the phosphorus that forms the backbone of DNA could be replaced with arsenic. This is highly doubtful as organisms prefer phosphate to arsenate and await further evidence. There are possibilities that boron and metal oxides form the basis of life. But the low abundance of boron remains an obstacle. Even on Earth, various modes of anaerobic respiration (without using oxygen) take place. Chlorine could serve as a good electron acceptor in place of oxygen. But chlorine is rare in the universe and often comes in the form of salts.
It may seem outrageous to talk about planets containing oceans of liquid platinum, life forms based on metal oxides, and sulfur dioxide atmospheres. The life form of a planet develops solely as a function of the components that compose it. On our own planet, oxygen was once in short supply, until plant life grew into giant trees like pine and released excess oxygen. The fossil records provide evidence of the development of larger fauna only after this era. So it is quite evident that the planetary condition and the evolving life form show a mutual dependence. Life as we know it could exist in the most unpredictable forms and it would be ridiculous to believe that humans are the most intelligent species. We would never know if we are still primitive organisms with only one specialized organ called the brain to brag about.