In search of extraterrestrial mind scientists often receive accusations in “carbon chauvinism” as they expect that other zhizneforma in the Universe will consist of the same biochemical construction blocks, as we, as appropriate building the searches. But life can quite be another — and people think of it — therefore let’s study ten possible biological and not biological systems which expand determination of “life”.
In 2005 Heather Smith from the International space university in Strasbourg and Chris Mackay from the Research center of Ames in NASA prepared the document considering the possibility of existence of life based on methane, so-called metanogen. Such life forms could consume hydrogen, acetylene and ethane, exhaling methane instead of carbon dioxide.
It could make possible life habitability zones in the cold worlds like the moon of Saturn the Titan. Like Earth, the atmosphere of the Titan is provided mostly by nitrogen, but mixed with methane. The titan also unique place in our Solar system, except Earth where there are big liquid reservoirs — lakes and the rivers from ethano-metane mix. (Underground reservoirs are also present at the Titan, its sisterly moon Enceladus, and also at the satellite of Jupiter to Europe). Liquid is considered necessary for molecular interactions of organic life and, of course, the main attention will be concentrated on water, but ethane and methane also allow such interactions to be performed.
The mission of NASA and ESA of Cassini-Huygens in 2004 observed the dirty world with a temperature of-179 degrees Celsius where water was firm as a stone, and methane floated on river valleys and pools to polar lakes. In 2015 the team of chemical engineers and astronomers of Cornell University developed a theoretical cellular membrane from small organic compounds of nitrogen which could function in liquid methane of the Titan. They called the theoretical cage “azotosomy” that in the literal translation means “a nitric body”, and it had the same stability and flexibility, as a terrestrial liposome. The acrylonitrile azotosoma was the most interesting molecular connection. Acrylonitrile, a colourless and poisonous organic molecule, is used for acrylic paints, rubber and thermoplastic on Earth; also it was found in the atmosphere of the Titan.
It is difficult to revaluate consequences of these experiments for searches of extraterrestrial life. Life not only potentially could develop on the Titan, but it also can be found on hydrogen, acetylene and etanovy traces on a surface. Planets and the moon in which atmospheres methane prevails can be not only around similar to the Sun of stars, but also around red dwarfs in wider “zone of the Goldilocks”. If NASA starts Titan Mare Explorer in 2016, in 2023 we will obtain the detailed information about possible life on nitrogen.
Life on the basis of silicon
Life on the basis of silicon is, perhaps, the most common form of the alternative biochemistry loved by popular science and a fantasy — remember a hort from “Star Trek”. This idea isn’t new, her roots go even to Herbert Wells’s reflections in 1894: “What fantastic imagination could be played from such assumption: let’s present silicon-aluminum organisms — or, maybe, at once silicon-aluminum people? — which travel through the atmosphere from gaseous sulfur, we will put so, by the seas from liquid iron temperature in several thousands of degrees or like that, slightly higher than temperature of the blast furnace”.
Silicon remains popular just because it is very similar to carbon and can form four communications, like carbon that opens a possibility of creation of biochemical system completely dependent on silicon. It is the most widespread element in crust, except for oxygen. On Earth there are seaweed which include silicon in the process of growth. Silicon plays a role, the second after carbon, as that can form stabler and various complex structures necessary for life. Carbon molecules include oxygen and nitrogen which form incredibly strong links. Difficult molecules on the basis of silicon, unfortunately, tend to break up. Besides, carbon is extremely spread in the Universe and there are billions of years.
Hardly life on the basis of silicon will appear in an environment, similar terrestrial as the most part of free silicon will be locked in volcanic and magmatic breeds from silicate materials. Assume that in a high-temperature environment everything can be in a different way, but haven’t found any proofs yet. Could maintain the extreme peace like the Titan life on the basis of silicon, perhaps, together with metanogena as silicon molecules like silons and polisilan can imitate organic chemistry of Earth. Nevertheless on the surface of Titanium carbon whereas the most part of silicon is deeply under a surface prevails.
The astrochemist of NASA Max Bernstein has assumed that life on the basis of silicon could exist on very hot planet, with the atmosphere rich with hydrogen and poor in oxygen, allowing to happen complex silon chemistry to the return silicon communications with selenium or tellurium, but it, according to Bernstein, it is improbable. On Earth such organisms would breed very slowly, and ours wouldn’t interfere with each other biochemistry in any way. They, however, could eat slowly our cities, but “it would be possible to apply a jackhammer to them”.
Other biochemical options
In principle, there were very many offers concerning the vital systems based on something another in addition to carbon. Like carbon and silicon, pine forest tends to form strong covalent molecular connections too, forming different structural options of hydride in which atoms of pine forest are connected by hydrogen bridges. As well as carbon, pine forest can contact nitrogen, forming connections, on chemical and to physical similar alkanes of property, the elementary organic connections. The main problem with life on the basis of pine forest is connected with the fact that it is quite rare element. Life on the basis of pine forest will be most reasonable in the environment which temperature is rather low for liquid ammonia, then chemical reactions will proceed more controlled.
Other possible life form which drew a certain attention is life on the basis of arsenic. All life on Earth consists of carbon, hydrogen, oxygen, phosphorus and sulfur, but in 2010 NASA declared that it found a bacterium of GFAJ-1 which could include arsenic instead of phosphorus in cellular structure without any consequences for itself. GFAJ-1 lives in the rich of myshyak lake Mono waters in California. Arsenic is poisonous for any living being on the planet, except several microorganisms which normally transfer it or breathe of GFAJ-1 became the first case of inclusion by an organism of this element as the biological construction block. Independent experts diluted a little this statement when didn’t find any certificates of inclusion of arsenic in DNA or at least some arsenates. Nevertheless interest in possible biochemistry on the basis of arsenic inflamed.
As a possible alternative to water for a construction of life forms also ammonia was pushed. Scientists assumed existence of biochemistry on the basis of nitrogen-hydrogen connections which use ammonia as the solvent; it could be used for creation of proteins, nucleinic acids and polypeptides. Any life forms on the basis of ammonia shall exist at low temperatures at which ammonia takes the liquid form. Solid ammonia is more dense than liquid ammonia therefore there is no method to stop its freezing in case of a cold snap. For unicells it wouldn’t constitute a problem, but would cause chaos for multicellular. Nevertheless there is a possibility of existence of monocelled ammoniac organisms on cold planets of the Solar system, and also on gas giants like Jupiter.
Sulfur, as believe, formed a basis to start metabolism on Earth, and the known organisms which metabolism included sulfur instead of oxygen exist in extreme conditions on Earth. Perhaps, in other world of a life form on the basis of sulfur could get an evolutionary advantage. Some consider that nitrogen and phosphorus could also take the place of carbon under quite specific conditions.
Richard Dawkins considers that the basic principle of life sounds so: “All life develops, thanks to mechanisms of survival of the reproduced beings”. Life shall be capable to be reproduced (with some assumptions) and to stay in the environment where natural selection and evolution will be possible. In the book “Selfish Gene” Dawkins noted that concepts and the ideas are developed in a brain and extend among people in the course of communication. In many respects it reminds behavior and adaptation of genes therefore he calls them “memes”. Some compare songs, jokes and rituals of human society to the first stages of organic life — the free radicals swimming in the ancient seas of Earth. Creations of reason are reproduced, evolve and fight for survival in a kingdom of the ideas.
Similar memes existed to mankind, in social appeals of birds and the acquired behavior of primacies. When the mankind became capable to think abstractly, memes gained further development, managing the breeding relations and creating a basis for the first traditions, cultures and religions. The invention of the letter pushed even more development of memes as they could extend in space and time, transferring memetichny information just as genes transfer biological. For some it is net analogy, but others consider that memes represent unique though a little rudimentary and limited life form.
Some went further away. Georg van Drim developed the theory of “simbiosizm” which implies that languages are life forms in itself. Old linguistic theories considered language something like a parasite, but van Drim believes that we live in a cooperation with the memetichesky entities inhabiting our brain. We live in the symbiotic relations with language organisms: without us they can’t exist, and without them we differ in nothing from monkeys. He considers that illusion of consciousness and free will poured out from interaction of animal instincts, hunger and lust of the person carrier and a linguistic simbiont which is reproduced by means of the ideas and meanings.
Synthetic life on the basis of XNA
Life on Earth is based on two molecules transferring information, DNA and RNA, and long time scientists reflected whether it is possible to create other similar molecules. Though any polymer can store information, RNA and DNA display heredity, coding and transfer of genetic information and are capable to adapt in the course of evolution eventually. DNA and RNA are chains of the molecules nucleotides consisting of three chemical components — phosphate, five-carbon sugar group (a dezoksiriboz in DNA or a ribose in RNA) and one of five standard bases (adenine, a guanine, цитозин, тимин or uratsit).
In 2012 the group of scientists from England, Belgium and Denmark first-ever has developed ksenonukleinovy acid (KHK, XNA), synthetic nucleotides, functionally and structurally reminding DNA and RNA. They have been developed by replacement of sugar groups of a dezoksiriboza and a ribose with various substitutes. Such molecules did earlier, but for the first time in the history they were capable to be reproduced and evolve. In DNA and RNA replication happens to the help of molecules of a polymerase which can read, transkibirovat and back transcribe the normal sequences of nucleinic acids. The group has developed synthetic polymerases which have created six new genetic systems: HNA, CeNA, LNA, ANA, FANA and TNA.
One of new genetic systems, HNA, or geksitonukleinovy acid, was rather reliable to keep the necessary number of genetic information which can serve in quality of a basis for biological systems. Other, treozonukleinovy acid, or TNA, was the potential candidate for the mysterious primary biochemistry reigning at sunrise lives.
There is a lot of potential applications of these achievements. Further researches can help with development of the best models of emergence of life on Earth and will have consequences for biological fabrications. XNA can receive therapeutic application, it is possible to create nucleinic acids for treatment and communication with the specific molecular goals which won’t spoil as quickly as DNA or RNA. They can even form the basis of molecular cars or in general an artificial life form.
But before it will become possible, other enzymes compatible to one of XNA have to be developed. Some of them have already developed in Great Britain at the end of 2014. There is also an opportunity that XNA can do harm to RNA / DNA organisms therefore safety has to be on the first place.
Chromodynamics, weak nuclear interaction and gravitational life
In 1979 the scientist and the nanotechnologist Robert Freytas Jr. assumed possible not biological life. He declared that possible metabolism of live systems is based on four fundamental forces — electromagnetism, strong nuclear interaction (or quantum chromodynamics), weak nuclear interaction and gravitation. Electromagnetic life is a standard biological life which we have on Earth.
Chromodynamic life could be based on strong nuclear interaction which is considered the strongest of fundamental forces, but only at extremely short distances. Freytas assumed that such environment can be possible on a neutron star, the heavy rotating object of 10-20 kilometers in the diameter with a mass of a star. With an improbable density, the most powerful magnetic field and gravitation in 100 billion times is stronger, than on Earth, such star would have a kernel with a 3-kilometer crust of crystal iron. Under it there would be a sea with incredibly hot neutrons, various nuclear particles, protons and atomic nuclei and possible “macrokernels” rich with neutrons. These macrokernels in the theory could create large a sverkhjyadr, similar to organic molecules, neutrons would act as a water equivalent in fancy pseudo-biological system.
Freytas saw life forms based on weak nuclear interaction as improbable as weak forces work only in the subnuclear range and aren’t especially strong. As often shows beta radioactive decay and free disintegration of neutrons, life forms of weak interaction could exist in case of careful control of weak interactions in the environment. Freytas provided the beings consisting of atoms with excessive neutrons which become radioactive when die. He also assumed that there are regions of the Universe where weak nuclear force is stronger, and, so chances of emergence of such life are higher.
Gravitational beings can exist too as gravitation is the most widespread and effective fundamental force in the Universe. Such beings could receive energy from the gravitation, receiving unrestricted food from collisions of black holes, galaxies, other heavenly objects; it is less being — from rotation of planets; the smallest — from energy of falls, wind, inflows and oceanic currents, perhaps, earthquakes.
Life forms from dust and plasma
Organic life on Earth is based on molecules with compounds of carbon, and we already found out possible connections for alternative forms. But in 2007 the international group of scientists led by V. N. Tsytovich from Institute of general physics of the Russian Academy of Sciences documented that under the necessary conditions of a particle of inorganic dust can be going to spiral structures which then will interact with each other in the manner inherent for organic chemistry. This behavior is also born in a plasma condition, the fourth condition of substance after firm, liquid and gaseous when electrons come off atoms, leaving the mass of charged particles.
Tsytovich’s group found out that when electronic charges separate and plasma is polarized, particles in plasma samoorganizutsya in a form of the spiral structures like a corkscrew electrically loaded and are attracted to each other. They can also share, forming copies of original structures, like DNA and induce charges in the neighbors. According to Tsytovich, “these complex, self-organized plasma structures meet all necessary requirements to consider them candidates for inorganic live matter. They are autonomous, they are reproduced and they evolve”.
Some sceptics consider that such statements are more attempt to draw attention, than serious scientific statements. Though spiral structures in plasma can remind DNA, similarity in shape optionally assumes similarity in functions. Moreover, the fact that spirals are reproduced doesn’t mean life potential; clouds too so do. What depresses even more, the most part of researches was conducted on computer models.
One of participants of an experiment also informed that though results really reminded life, eventually, they were “just special form of a plasma crystal”. And still, if inorganic particles in plasma can develop into the replicating, developing life forms, they can be the most common form of life in the Universe, thanks to ubiquitous plasma and interstellar clouds of dust on all space.
Inorganic chemical cages
Professor Li Kronin, the chemist of College of science and engineering at University of Glasgow, dreams to create living cells from metal. He uses polioksometallata, a number of the atoms of metal connected with oxygen and phosphorus to create bubbles, similar to cages, which he calls “inorganic chemical cages” or iCHELLs (this acronym can be translated as “neokhletka”).
Kronin’s group has begun with creation of salts from negatively charged ions of the large oxides of metal connected with a small positively charged ion like hydrogen or sodium. Solution from these salts then is injected into other salt solution full of the big positively charged organic ions connected with small negatively charged. Two salts meet and exchange parts so large oxides of metal become partners with large organic ions, forming something like a bubble which is impenetrable for water. Changing frame of oxide of metal, it is possible to achieve that bubbles will gain properties of biological cellular membranes which selectively pass and produce chemicals from a cage that potentially is able to allow course of the same type of controlled chemical reactions which occurs in living cells.
The group of scientists has also made bubbles in bubbles, imitating internal structures of biological cages, and has achieved progress in creation of an artificial form of photosynthesis which can be potentially used for creation of artificial cages of plants. Other synthetic biologists note that such cages can never become live, won’t receive system of replication and evolution like DNA yet. Kronin doesn’t lose hope that further development will bear fruit. Among possible use of this technology there is also a development of materials for solar fuel devices and, of course, medicine.
According to Kronin, “the main objective is to create complex chemical cages with live properties which can help us to understand development of life and to go the same way to introduce new technologies on the basis of evolution in a material world — some kind of inorganic live technologies”.
Probes Neumann’s background
Artificial life on the basis of machines is quite widespread idea, nearly banal therefore just let’s consider probes Neumann’s background not to avoid it. For the first time they were thought up in the middle of the 20th century by the Hungarian mathematician and the futurologist John von Neumann who considered that to reproduce functions of a human brain, the machine shall possess mechanisms of self-government and self-recovery. So he came up with the idea creations of self-replicating machines at the heart of which observations of the increasing complexity of life in the course of reproduction work. He considered that such machines can become some kind of universal designer who could allow not create complete remarks of, but also improve or change versions, thereby performing evolution and increasing complexity with time.
Other futurologists like Freeman Dayson and Eric Dreksler quickly enough applied these ideas to area of space exploration and created the probe Neumann’s background. Sending the self-replicating robot to space can be most in an efficient manner colonizations of a galaxy, it is so possible to take all Milky Way less than for one million years, even being limited by velocity of light.
Kak explained to Michio Kak:
“The probe Neumann’s background is the robot intended for achievement of far star systems and creation of factories which will build copies themselves in thousands. The dead moon, even not planet, can become an ideal destination for probes Neumann’s background as there will sit down and fly up more simply from these moon and also because on the moon there is no erosion. Probes could live at the expense of the earth, extracting iron, nickel and other raw materials for a construction of robotic factories. They would create thousands of copies themselves which then would disperse in search of other star systems”.
Various versions of the basic idea of the probe Neumann’s background, including probes of development and investigation for a silent research and observation of extraterrestrial civilizations were for many years thought up; the probes of communication scattered on all space better to catch radio signals of aliens; working probes for a construction of supermassive space structures; probes colonialists which will conquer other worlds. There can be even guiding probes which will remove young civilizations in space. Alas, there can be also probes berserkers which task will be a destruction of traces of any organic chemistry in space what the construction of police probes which these attacks will reflect will follow. Considering that probes Neumann’s background can become some kind of space virus, we should approaching their development carefully.
In 1975 James Lavlok and Sidney Epton jointly wrote article for New Scientist under the name “Searching Gays”. Adhering to the traditional point of view that life arose on Earth and prospered thanks to the necessary material conditions, Lavlok and Epton assumed that life thus undertook an active role in maintenance and determination of conditions for the survival. They assumed that all live matter on Earth, in air, oceans and on a surface is a part of the single system behaving like a superorganism which is capable to adjust temperature on surfaces and composition of the atmosphere in a way, necessary for survival. They called such system Gey, in honor of the Greek goddess of the earth. It exists to support a homeostasis thanks to which on the earth there can be a biosphere.
Lavlok worked on a hypothesis Gays with the middle of the 60th years. The main idea is that the biosphere of Earth has a number of natural cycles and when one goes wrong way, others compensate it so that to support a vital capability. It could explain why the atmosphere doesn’t consist entirely of carbon dioxide or why the seas not too salty. Though volcanic eruptions made the early atmosphere consisting mainly of carbon dioxide, there were bacteria and plants making oxygen in the course of photosynthesis producing nitrogen. Later millions of years the atmosphere changed in our advantage. Though the rivers transfer salt to oceans from breeds, salinity of oceans remains stable for 3,4% as salt filters through cracks in oceanic day. These are not conscious processes, but result of feedback which keeps planets in balance, suitable for dwelling.
Other certificates include that if not biotic activity, methane and hydrogen would disappear from the atmosphere of everything for several decades. Besides, despite increase in temperature of the Sun by 30% for the last 3,5 billion years, average global temperature reeled on only 5 degrees Celsius, thanks to the regulatory mechanism which deletes carbon dioxide from the atmosphere and locks it in fossilized organic matter.
Originally Lavlok’s ideas were met by sneers and accusations. Over time, however, the hypothesis Gays affected the ideas about the biosphere of Earth, helped to create their integral perception in a scientific world. Today the hypothesis Gays is respected rather, than is accepted by scientists. It is rather positive cultural frame in which scientific research on Earth as a global ecosystem shall be conducted.
The paleontologist Peter Ward developed the competitive hypothesis of Medea called in honor of mother who killed the children, in the Greek mythology which main idea comes down to the fact that life in essence aims at self-damage and suicide. He specifies that historically the majority of mass extinctions were caused by life forms, for example, microorganisms or hominids in trousers which put heavy mutilations to the atmosphere of Earth.