Theory Life in the Universe

A symbolistic illustration of the life in the Universe. picture site 'Amateur Astronomy'

Life in the Universe is an old question, and of a philosophical nature. Quest for life has been sporadic by space age beginnings as it recently became a NASA motto. Missions are now searching life-favourable environments at Mars, as some gas giants moons, like Europa at Jupiter, are centers of interest too. From most evidence it appears that the Universe is life-friendly and, based on history of life on Earth, life is clever and is intimately linked to its environment. Life as we know it at Earth requires three primary ingredients: liquid water; a source of energy for metabolism; and the right chemical ingredients, primarily carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. The most basic set of chemical elements life typically needs is summed up by the acronym CHNOPS, or the letter signifiers of the elements carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. No life can exist in hyperacidic, hypersaline or too magnesium-rich water. Phosphorus seen at a comet like Rosetta likely found its origin in a protoplanetary disk. Phosphorus is a building block of DNA. Other precursors to life -- including salts of ammonium (the only place where nitrogen is found on a comet) and a particular type of hydrocarbons were also found and having the same origin. The main building blocks of life, like carbon, nitrogen and oxygen, may be produced by supernovas, red giants and other evolved stars. The development of minerals -- which counted by 270 only when Earth began its geological history -- plaid a role in the emergence of life as clay, as it features a layered structure, like allowed encapsulation of the first biotic elements. Chemical reactivity occurs on a gradient of chemical ingredients' strength at donating or receiving electrons. Transfer of electrons due to this gradient can provide energy for life. Chemicals needed to form terrestrial planets, like iron, magnesium, silicon and sulfur are common in the Universe alike with the chemical requirements for life. 'Organohalogens' consist of halogens, such as chlorine and fluorine, bonded with carbon and sometimes other elements as such compounds are created by some biological processes on Earth. Rather than indicating existing life, those compounds might be involved in the origin of life. A young planetary system further, can inherit the chemical composition of its parent star-forming cloud and opens up the possibility that organohalogens could arrive on planets in young systems during planet formation or via comet impacts. Frigid molecular clouds has dust shielding against destructive ultraviolet light and aid chemical reactions as they hold most of the water in the Universe. Varied elements glue to dust grains and yielding other elements. Such grains are swept by planets when they form and are thus delivered with materials needed for life. Magnetospheres likely are a key to sustaining life on a planet because it protect from radiations and atmosphere erosion. A complex network of reactions must have arisen to make organic molecules from carbon dioxide, or possibly from other inorganic sources of carbon such as carbon monoxide or cyanides, as a suitable complex reaction network can develop from just two simple organic constituents, namely, glyoxylate and pyruvate in the presence of ferrous iron. Possible traces of life in terms of research, can be morphological or chemical but abiotic processes that mimic or alter them, or subsequent contamination, may challenge their interpretation

Life appearance now is considered possible in two ways. Life, first may appear from a brew of various chemicals as triggered further by lightning as demonstrated by the famed, 1953 experiment led by chemists Stanley L. Miller and Harold C. Urey (as lightnings themselves can yield amino acids and sugars). Or life is thought to be able to appear at the interface between under-ocean vents and water, when gases coming out of the vent comes to contact with a suitable oxidant like carbon dioxide. NASA scientists by 2019, have reproduced in the lab how the ingredients for life could have formed deep in the ocean 4 billion years ago, and formed amino acids and alpha hydroxy acids. Once the life mechanism started, it then requires an environment of liquid water, essential elements and nutrients, and an energy source. Life mostly comes on Earth under three forms, eukaryotes (unicellular organisms with a nucleus), prokaryotes (unicellular organisms with no nucleus) and the most ancient, archaea as giant virus, which have been recently discovered with a large genome allowing to a more active role than smaller forms might constitute a fourth form of life. In any case, such mega-virus should be included into any evolutionary study of life. As far as molecule building is concerned, carbon is great for a large variety of those because it is available almost everywhere with only hydrogen, helium and oxygen more plentiful in the Universe. Thus, carbon is able to build molecules in all kinds of configurations, with millions of carbon compounds identified, and especially for building very stable molecules. In the Miller and Urey, 1953 experiment, a mix of gases was exposed to a lightning-like electrical discharge. A variation of the experiment in 1958 occurred with added a mix of volcanic gases like hydrogen sulfide, methane (the simplest organic molecule), ammonia and carbon dioxide, as results never had been analyzed. Recentest analyses show that preserved samples contained sulfur-containing amino acids. That likely hints to that primordial life on Earth appeared in volcanoe-ladden areas combined with lightning activity, not taking in account amino acids formed in outer space and brought by comets or asteroids. Varied carbon-rich meteorites usually harbours too amino acids. Carbonaceous chondrites, for example, a class of meteorites, feature organic compounds as meteorites, generally, also do. Amino acids are the building blocks of proteins, the workhorse molecules of life, used in everything from structures like hair to enzymes, the catalysts that speed up or regulate chemical reactions. Hence amino acids combine to form proteins which turn into cellular structures and controlling reactions therein generally. They likely formed from varied components in varied environments in the early Earth or Universe, as the experiment of 1953 indeed mostly yielded a mix more like the primordial atmosphere of the Earth! Some scientitsts now state that the Universe, at some level 'seems to be hard-wired to create amino acids.' Amino acids, due to their miscellanesous native environments lend support to the theory that a 'kit' of ready-made parts created in space and delivered to Earth by meteorite and comet impacts gave a boost to the origin of life. Amino-acids as found in carbon-rich meteorites usually are yielded through relatively low-temperature process involving water, aldehyde and ketone compounds, ammonia, and cyanide or a'Strecker-cyanohydrin synthesis,' as a higher-temperature process involving gas containing hydrogen, carbon monoxide, and nitrogen called 'Fischer-Tropsch' –type (FTT) reactions may also occur. For a alien world to harbour life like we know it, three ingredients should be needed, with organic molecules able to build life, energy for that and liquid water, which hints to that that planet should have to be extremely similar to Earth to feature all three data. A far-fetched question is whether life could exist that doesn't require water, which however cannot be ruled out. Color of life is variable. Green is the sign that sunlight carbon dioxide and water are the object of photosynthesis as at Earth, for example, life may have been purple before that should microbes have used some molecule other than chlorophyll. Iron too is a ingredient to life as iron deposits in thermal source are favorable to life

NASA Astrobiology Institute's JPL Icy Worlds team has built in 2013 a series of glass tubes, thin barrels and valves with a laser and a detector system to mimic the conditions at hydrothermal vents at the bottom of Earth's ocean and also detects compounds coming out of it, based upon carbonic-fizzy ocean water and the alkaline fluid. Both liquids sent through a sample of rock that simulates ancient volcanic ocean crust could lead to the formation of simple organic molecules such as ethane and methane, and amino acids. The origin of carbon however is still ill-known. This experiment has its roots in a theory from Russell in 1989 that moderately warm, alkaline hydrothermal vents at the bottom of the ocean could have hatched life about 4 billion years ago. The ancient ocean at these vents contains carbon dioxide, which provides the supply of carbon that could be reassembled into organic molecules. Extreme cold, hard vacuum, and high radiation environment of space allows the formation of an unstructured form of solid water called amorphous ice. Often particles and organic compounds are trapped in this ice that could provide clues to life in the universe. Scientists by early 2017, evidenced the presence of putative fossilized microorganisms between 3,8 billion and possibly 4,3 billion years old in seafloor-hydrothermal vent-related precipitates. Electrical energy naturally produced at the sea floor might have given rise to life, or a hypothesis called 'submarine alkaline hydrothermal emergence of life' as 'unbalanced states' are prone to life like in ponds found on early Earth, or like the electrical gradient originating between hydrothermal fluids and the ocean. Carbon dioxide-rich oceans and hydrogen and methane along submarine vents triggered electrons' transfer which produced more complex carbon-containing, or organic compounds. Minerals along the chimney further provided for more life fuel, acting like enzymes. Life's places, at the origin of the latter 3.5 billion to 4.4 billion years ago, are enriched in iron- and magnesium-containing minerals, and in other elements that could have been extracted from rock in a process mediated by high-temperature water, strongly pointing to hydrothermal activity at that time. That was due to the heat from the mantle was too great for plate tectonics to occur as heat would have been lost from Earth’s interior mainly through volcanoes on the ocean floor. Earth’s crust would have been rich in silicate minerals and iron, allowing high rates of serpentinization. Serpentinization -- chemical interaction between water and a type of rock called peridotite that contains minerals enriched in magnesium, iron and silica -- is another type of hydrothermal-vent environment and it produces hydrogen and a variety of organic molecules, or amino acids synthesized there by chemical reactions that do not require biological input, as a abiotic generation of amino acids generally occurring in usual hydrothermal vent

Life generally, lives off proton gradients and the transfer of electrons. Like proton gradients, electron transfer processes occur regularly in mitochondria, for example. Vitamin B3 was also delivered Earth by carbon-rich meteorites; that vitamin, or the nicotinic acid or niacin, is a precursor to NAD (nicotinamide adenine dinucleotide), which is essential to metabolism. Vitamin B3 likely was found on asteroid surfaces not contaminated by water. Odd orbits' tilts which cause a planet to wobble could make those habitable a the climate effects generated on these wobbling worlds in timelength within tens to hundreds of thousands of years could prevent them from turning into glacier-covered ice lockers, even when far from their mother-star

Universe is Life-Friendly

Life exists in a myriad of forms, but if you break any organism down to its most basic parts, it's all the same basics, carbon atoms connected to hydrogen, oxygen, nitrogen and other elements. Carbon and hydrogen like to get together as that is true for the whole Universe where that formed in abundance, making the rudimentary material scientists call organic. First life-building molecules were observed in a molecular cloud in the early 1940s. When a molecule absorbs a photon of light, it becomes excited and has more energy to react with other particles. In the case of a hydrogen molecule, the hydrogen molecule vibrates, rotates faster or both when hit by an ultraviolet photon. Such a heating of hydrogen regions in a molecular cloud by ultraviolet light is creating the prime conditions for forming hydrocarbons resulting from carbon ions originally formed in stars and reacting with the hydrogen, creating CH+. Eventually the CH+ captures a electron to form the neutral CH molecule. Ultraviolet light from stars plays a key role in molecular clouds in creating life-building molecules, rather than 'shock' events that create turbulence, as was previously thought (shocks are events that create a lot of turbulence, such as exploding supernovae or young stars ejecting material as shock waves, with the vibrations they cause, can knock off electrons from atoms and turn them ions, which are more likely to combine. At the NASA they consider that strong indications of life beyond Earth will be discovered within a decade and definitive evidence within 20-30 years from 2015. We are one generation away from life discovered on a icy Moon or Mars in the solar system and one more generation on a nearby exoplanet

->Life Everywhere In the Universe
The life is really everywhere in the Universe, a recent, October 2005 study shows. It was already known that the complex organic molecules polycyclic aromatic hydrocarbons (PAHs) were found all along the Universe. PAHs are flat molecules consisting of carbon atoms arranged in a honeycomb pattern, surrounded by hydrogen. PAHs are also found in ash from coal, wood and oil fires on Earth. PAHs make up about 10 percent of the carbon in the Universe. The study however demonstrated further that polycyclic aromatic nitrogen heterocycles, or PANHs, the real building blocks of life - containing nitrogen, they are at the base of DNA- are formed in stars and expulsed when these die as supernovae, forming the lion's share of the PAHs. PHAs were found in 2013 to glow in the infrared as they significantly change in size, electrical charge and structure, to adjust to the different environment where they reside, like close to star radiation or inside dark molecular clouds. Carbon is one of the most abundant atoms in space as large PHAs found in clouds then break down and get stripped from hydrogen through a nitrogen-based process. Other studies, on the other hand, have shown that PHAs can survive even the hard conditions of a nearby supernova explosion. Other findings, for example, saw that sugar molecules exist in the gas surrounding young stars, to be included in planets forming there. As they are hit by ultraviolet radiation from stars in a nebula, smallest PAHs are destroyed as medium-sized molecules irradiated, so they combine into larger molecules. That growth of complex organic molecules is one of the steps leading to the emergence of life. As soon as their origin like protostars, Sun-like stars harbor traces of methyl isocyanate, a chemical building block of life. Double, or triple stars as such their mass push the goldylock zone away might be not that defavourable to life

Heavier chemical elements from carbon on up are produced and distributed into interstellar space by stars that explode as supernovae at the ends of their lifetimes. Planetary nebulae play a as crucial role in the chemical enrichment and evolution of the Universe than supernovae. Elements such as carbon and nitrogen, as well as some other heavier elements, are created in these stars and returned to the interstellar medium. This chemical dispersal continues at progressively larger scales through other mechanisms, such as galactic outflows, interactions and mergers with neighboring galaxies, and stripping caused by a galaxy's motion through the hot gas filling galaxy clusters. Such heavier elements were distributed across millions of light-years early in cosmic history, more than 10 billion years ago. The stellar contribution occurred likely between 2 and 4 billion years old, a period when stars were being formed at the fastest rate in cosmic history. In other words, the chemical requirements for life are common throughout the Universe. Before the Universe is one billion years old all the various atomic elements have been created by stars. Such elements, coated on dust grains found in well-known large interstellar clouds, are rapidly producing molecules. Water and ammonia are found in quantity as are organic molecules. Vitamin B3 could have been made on icy dust grains in space, as it is also known as niacin or nicotinic acid, is used to build NAD (nicotinamide adenine dinucleotide), which is essential to metabolism and probably ancient in origin. NASA's Spitzer Space Telescope have confirmed in 2005 that large molecules known as polycyclic aromatic hydrocarbons, which are the building blocks of life, are found at an age of the Universe which was thought not to have some. In this case at an Universe 3.5 billion years old. This is 1 billion years earlier than any such building blocks previously observed. Such complex molecules form any time carbon-based materials are not burned completely. The Orion nebula, a gas cloud well known to the amateurs astronomers, in constellation Orion, the Hunter, is known to be one of the most prolific chemical factories in space, although the full extent of its chemistry and the pathways for molecule formation are not well understood. Astronomers have identified a few common molecules then that are precursors to life-enabling molecules, including water, carbon monoxide, formaldehyde, methanol, dimethyl ether, hydrogen cyanide, sulfur oxide and sulfur dioxide. Hence such life fundamentals are found back too in protoplanetary disks, there where planets may form around a forming star. Complex organic molecules have been officially discovered in a protoplanetary disc surrounding a young star in April 2015. Water itself has been recently found to be extant since the very beginning of the Universe, and mostly under the form of 'masers' those disk of water surrounding some galactic black holes in galaxies! Water in space might be related to the ultraviolet radiation of stars, as evidence by a study of the enveloppe of so-called 'carbon star' -which was close to dying, a variety which is known not to produce much water. The ultraviolet light creates water by breaking carbon monoxide molecules and letting the oxygen atom free, which can bond with hydrogen ones. Warm water vapor was also found current in protoplanetary disks, and recent finds also found that cold water vapor extending into the far reaches of those is current also, allowing for more icy comets which later will bring that water to new-formed planets. Carbon, water and energy look like the prerequisites for life. Organic chemicals consist of carbon and hydrogen and, in many cases, additional elements. They can exist without life, but life as we know it cannot exist without them. Organics delivered by meteorites without involvement of biology on the other hand, come with more random chemical structures than the patterns seen in mixtures of organic chemicals produced by organisms. Oxygen molecules in space were discovered in the Orion star-forming complex. Such molecules might be locked up in water ice that coats tiny dust grains and formed after starlight warmed the icy grains, releasing water. Water may also surround quasar showing how water is pervasive throughout the Universe, even at the very earliest times. Water vapor is also found in galaxies, like our own Milky Way as most of the water then is frozen in ice. Graphene is also found in space, a element first synthesized in a lab in 2004, strong and thin conducting electricity as well as copper. It belongs to the fullerene family and might be shed by planetary nebulae events or form in hydrogen-rich environments, due to shock waves generated by a supernova and breaking apart hydrogen-containing carbon grains. That family of elements also includes molecules called 'buckyballs,' or C60s. These carbon spheres contain 60 carbon atoms arranged like a soccer ball. They have been found in meteorites carrying extraterrestrial gases, and water very recently encapsulated in buckyballs. Fullerenes may have helped transport materials from space to Earth long ago, possibly helping to kick-start life

Supernovae as they release elements created by a star during its lifetime are also purveyors to life. Planetary nebulas also contain a large proportion of the lighter elements of life such as carbon, nitrogen, and oxygen, made by nuclear fusion in the parent star as more might be triggered through the interaction due to the UV radiation of the remnant white dwarf, as intense radiation may also destroy molecules that had previously been ejected

Prebiotic basic elements are found in the protoplanetary discs which are seen around a star forming, whence the planets are forming. Thus they are likely found back about any planetary rocky -or even gases- chemistry. The asteroidal, meteoroidal, or cometary collisions occurring against the planets, like during the Heavy Bombardment Period in the solar system, about 3.9 billion years ago, further brings additional prebiotic elements there. Such that quantity further is added with that Earth also receives extraterrestrial material in the form of dust from comets and asteroids. Scientists have long debated that water and organic molecules were brought by asteroids and comets to the young Earth albeit not all the comets explored until now by planetary missions may fit the bill. Hints of the simplest amino acid, glycine, were found in samples returned in 2006 from Comet Wild-2 by NASA’s Stardust mission, with a doublt of possible contamination however. A strong link has been observed between glycine and cometary dust, suggesting that glycine likely released, perhaps with other volatiles, from the icy surface of dust grains once warmed up in comets' coma. Glycine, on a other hand, the only amino acid that is known to be able to form without liquid water likely within interstellar icy dust grains or by the ultraviolet irradiation of ice and conserved in comets, for example, for billions of years. The asteroids and comets of the ancient times, in any case were guardians of how the material in the primitive solar system was like, as that material eventually ended up in the prebiotic soup whence life emerged. Some comets have been found releasing ethyl alcohol, adding to the evidence that comets could have been a source of the complex organic molecules necessary for the emergence of life. Complex life in exo-solar systems might depend upon the size and location of an asteroid belt, shaped by the evolution of the star's protoplanetary disk and by the gravitational influence of a nearby giant Jupiter-like planet. Asteroid collisions with planets are hazardous as they also provide a boost to the birth and evolution of complex life. According to the theory of punctuated equilibrium, occasional asteroid impacts might accelerate the rate of biological evolution by disrupting a planet's environment to the point where species must try new adaptation strategies. Life in a exo-solar system might thus depend upon the presence of a Jupiter-like planet coralling a asteroid belt in just the appropriate manner. Most exo-Jupiters however looks like they migrated to far inwards their star to preserve a asteroid belt. A recentest study of the samples brought back from comet Wild 2 by the Stardust mission in 2006, is well showing how glycine, the simplest amino acid used to make proteins, was found at NASA's Goddard Space Flight Center. Periodical bursts at the surface of comets due to sublimation of ice layers when exposed to the Sun for cause of the comet's rotation, might be too at the origin of the dispersion of life-related components in the early solar system. Clouds of cometary dust and particles likely were in number at a time when the remnants of the solar system formation were roaming in number. The strong, ultraviolet radiation of a forming star, on the other hand, is triggering the formation of more life-forming elements still. Scientists now think that planets around stars cooler than our Sun likely possess a different mix of prebioticchemicals, bringing, maybe to a less capability in terms of life of the 'Super-Earths', which are found like exoplanets around such stars like the M and brown dwarfs. Such stars, further, are enduring strong magnetic explosions which are another hindrance to the development of life!

The idea that comets brought water on the planets in the inner solar system was fashionable by a epoch as it had since faded somehow. It was reinforced by 2011 when the ESA Herschel Space Observatory showed that comet Hartley 2, which comes from the distant Kuiper Belt, contains water with the same chemical signature as Earth's oceans. Icy, rocky bodies including Pluto, other dwarf planets and innumerable comets likely plaid a major role. Until now water found in comets were not isotopically the same than that found at Earth, or 'heavy water' with one of the two normal hydrogen atoms replaced by the heavy hydrogen isotope known as deuterium. Comets from the Oort Cloud until now had been found with such a feature, albeit lesser as comets there likely formed in the inner solar system -and therefore with less water- before being tossed out to such great distances

On the other hand, proto-cells and self-replicating molecules may naturally originate from such inorganic and organic molecules. A pair of simple compounds, which would have been abundant on early Earth could have given rise to a network of simple reactions that produce the three major classes of biomolecules, nucleic acids, amino acids, and lipids needed for life, along with RNA. RNA might have been the pionneer of life as it carries genetic information and also serves as a proteinlike chemical catalyst, speeding up certain reactions. At 4 billion years ago, much of Earth might have been blanketed with a greyish-brown kind of mineral, consisting of crystals of the organic molecules now called A, U, C and G. And some of these would later serve as the building blocks of RNA, the evolutionary engine of the first living organisms, before DNA existed. A other view is that metabolism came first and that simple metal catalysts may have created a soup of organic building blocks. Self-replicating molecules are the precursors for the RNA and the DNA these fundamentals of life. It is radiation like the ultraviolet which processes basic elements into more complex ones and it is water which has them develop a membrane. Naturally! Scientists by March 2015, as they were studying the origin of life have reproduced uracil, cytosine, and thymine, all part of the genetic code found in RNA or DNA, in the laboratory. Such elements were produced from a ice sample containing pyrimidine exposed to ultraviolet radiation under space-like conditions.The molecule pyrimidine is found in meteorites and features nitrogen atoms, although scientists still do not know its origin. It may be similar to the carbon-rich PAHs, in that it may be produced in the final outbursts of dying, giant red stars, or formed in dense clouds of interstellar gas and dust. Nitrogen atoms make the molecule less stable and more susceptible to destruction by radiation. Molecules of pyrimidine could survive long enough to migrate into interstellar dust clouds and might be able to shield themselves from destructive radiation, freezing into dust grains inside dust clouds which provide shielding. Such results suggest that once the Earth formed, many of the building blocks of life were likely present from the beginning, which likely is true wherever planets form. The accumulation of such proto-cells and such self-replicating molecules at some places on a planet or a moon may be the leading path to life. Proto-RNA and DNA become encapsulated into proto-cells, forming an obvious basis for a further evolution. Some asteroids may have behave like "molecular factories" cranking out life's ingredients and shipping them to Earth via meteorite impacts. Some kind of extraterrestrial molecules, including amino acids or building blocks of proteins might have look less like a rigid assembly line and more like a flexible set able to adapt. Some pieces of material from a same exploding asteroid thus may display a large variety of what kind of basic molecules were brought on a given planet. The process likely is linked to the interaction of materials with water already present on a planet. Water percolating through the asteroid's pieces caused some molecules to be formed and others destroyed. A way, generally, to found out whether a amino acid came from space is to look at what isotopes it contains. Isotopes are versions of an element with different masses; for example, carbon 13 is a heavier, and less common, variety of carbon. Amino acids enriched in the heavier carbon 13 were likely created in space. Also cosmic radiations might have been part of the screenplay as able to trigger some mutation in the DNA, for example. By 2011 one found that some building blocks of DNA found in meteorites were likely created in space hinting to that ready-made parts are created in space and delivered to Earth by meteorites and comets. Such parts are due to the chemistry inside asteroids and comets, like amino acids in comet Wild 2, which are used to make proteins, the workhorse molecules of life. There seems to be a 'goldilocks' class of meteorite, the so-called CM2 meteorites, where conditions are just right to make more of these molecules. A model also found by 2012 that high-energy ultraviolet radiation can turn simple ices like those found in the solar system primitive nebula into a rich mixture of organics like molecules of biological interest, including amino acids, nucleobases, and amphiphiles, the building blocks of proteins, RNA and DNA, and cellular membranes, respectively. Such ice grains are also suppose to move in and out of warmer regions in the nebula, completing the recipe for making organic compounds: ice, irradiation, and warming!

->More About DNA and RNA
Backbone of DNA and RNA molecules is constituted of phosphorus. As far as the DNA is concerned, it is a molecule which is composed from chemical elements -they are called the 'nucleotides.' Four basic units make up DNA adenine, guanine, thymine and cytosine or the DNA sequencing, and written as strings like ATCGGTGA, etc. Letters of DNA pair up because they form hydrogen bonds as each contains hydrogen atoms, which are attracted to nitrogen or oxygen atoms in their partner. That list of nucleotides recently expanded from four to six as number 7 and 8 further were discovered. A process, called methylation,causes the DNA's double helix to fold even tighter upon itself. DNA resembles a spiral ladder. Adenine and guanine connect with two other nucleobases to form the rungs of the ladder. They are part of the code that tells the cellular machinery which proteins to make. A gene is a string of nucleotides. Nucleotids themselves are formed from a base made of nitrogen, with sugars and one or more phosphorated groups (phosphorus). Such chemical compounds are transforming the amino-acids. The amino-acids are molecules containing both an 'amine" -an organic element based on nitrogen with groups of acidic atoms which are themselves at the basis of chemical reactions, and based too on carbon- into proteins. The proteins are large organic compounds, which are arrangements of amino-acids as they are linked into them. The transformation of the amino-acids into proteins is made through the genetic coding. The genetic coding establishes a correspondance between the nucleotids and the amino-acids. It somehow is containing the sequence of amino-acids which are to be found in such or such protein; they are 20 such standard codings. Proteins, in turn, with sugars and nucleidic acids, serve to the metabolism of the living cells and the living creatures. They are catalysing the chemical reactions from the molecules, speeding up or regulating those; they are participating into the cells' cyto-skeleton -like their forms or motion; they allow the exchange of informations -via receptors, etc.- between cells. Proteins too are allowing for the immune defense of the cells against viruses and bacteriae. They allow the junction between the cells and the cycle of the cellular division which, for the embryo, for example, is allowing for the developement, through a differentiation process, of it. For a grown up organism, this mechanism is allowing for the renewal of skin, of the blood cells, the hair, etc. Humans, for example, have about 23,000 protein-coding genes, a mere 1.5 percent of the genome. The rest is made up of what was first called "junk DNA,' including fragments of DNA that don't code for any proteins and chunks of genes that regulate other portions of the genome. Recently, scientists however found that at least 80 percent of the genome is indeed biologically active, with much non-protein-coding DNA regulating nearby genes in a complex system of influence. 'Transposable elements' in a genome are movable and repeated ADN sequences considered powerful engines to evolution as they however may be counterbalanced by environmental factors
. The process through which one goes from the DNA coding to the proteins is made through the RNA. The RNA too is a molecule, which is composed of chemical compounds. Those compounds are different from those of the DNA as they are mostly sugars and nitrogen too. The RNA is created by enzymes from the DNA. The enzymes are proteins. The RNA, thus, is transfering the amino-acids into the ribozome, that location in a cell where, technically, proteins are formed. RNA might be the precursor to DNA as it would feature a same skeleton, alternating phosphate and sugar, to which 4 bases hang. Life might have descended from RNA self-assembling from bases such as ribose, a organic sugar molecule, which needs a stabilize. Already stabilized ribose might have come from Mars, or boron, a stabilizer, might also have lied in oceans at Earth. In 2013, a second coding mechanism was found inside DNA. Instead of instructing about proteins like the basic DNA does, that one is for handling gene control programs, as that might allow to DNA mutations. Il appears to stabilise certain beneficial features of proteins and about their production
By humans, the ribbons constituting the DNA, technically are combining themselves into more complex elements, which in turn combine themselves into filaments. Those filaments are winding themselves in turn into the chromosoms. By the humans, moreover, the 'mitochondrial DNA' is participating into that process as it combines with the 23 chromosoms of both parents to form the genome of the egg. Mitochondrial DNA determines a living being's mitochondria, or the powerhouses of cells. It is transmitted from the subject's mother and any mutations in mitochondrial DNA carried by males are not passed on to the next generation, which slows natural selection. The mitochondrial DNA is more or less similar to the regular DNA as, however, it's contained into the mitochondriae. That difference between the DNA and the mitochondrial DNA is found by all living beings
. Proteins, as far as alimentation is concerned, are amino-acids themselves. Glucids are sugars; they are hydrocarbons. Fats are fats. Nitrogen is constituting the Earth's atmosphere for about 80 percent of it as it is extent into the proteins, the amino-acids. During the nurturing process, in a human, nitrogen is rejected under the form of ammonia (which is transformed into urea, or the uric acid). Carbon forms the basis of varied chemical compounds, like coal, oil, graphite, or diamonds, etc. Carbon thus -the carbon proper, and sugars- is, along with nitrogen, the main component of life
. As DNA and RNA are nucleic acids, cyanobacteries 3.5 billion years ago were manufacturing a basic molecule to a other type of nucleic acid, or the peptidic nucleic acids

Life too, based on what is seeable from the geological history of Earth, may develop outside the cycle of the oxygen-friendly photosynthesis about which it is working nowadays. Life at Earth has been found being able to work upon chemosynthesis or non-oxygen-producing photosynthesis. Currently so far, extremophiles found at Earth are hinting to what extreme conditions life might withstand elsewhere in the Universe. First, life is not repeled by extreme heat (organisms may life at temperatures as high as 235° F (113° C), and up to 662° F (350° C), extreme cold (bacteria have been found in Alaska to have survived a 32,000-year frozen state and back to life when the ice melted), deep-underground conditions (organisms have been found as deep as 2 miles -which, among others, means no light; such dark-dwellers have extremely slow metabolisms, with some organisms moving the equivalent of just a few electrons per second as many spend their lives bound to minerals) nor extreme pressure (life found miles below the surface of the ocean, at hydrothermal vents). Life further seems to be resistant too to the most acidic environment (acidic water for example, with a pH of 0.0 -that is as acidic as battery acid) or to the most radiation-ladden one (organisms have been found resistant to 1.5 million rads, that is a thousand times more than any other form of life, or too these "Streptococcus mitis" found by the Apollo 12 mission as left at the Surveyor 3 lunar lander). A form of life has even been found at deep-underwater mounds of methane-rich ice. One of the most important factor for life seems well to be heat, which can provide for the lack of light or an excess of pressure. Adaptability to other conditions like acid, radiation or exotic elements might be more specific. Polyextremophiles further are bacteria which can live among a series of extreme conditions found in a one place, like in Lake Diamante, in Argentina northwest, in the center of a giant volcanic crater located over 15,400 feet above sea level. With levels of arsenic 20,000 times higher than the level regarded as safe for drinking water and temperature often below freezing, with salty water preventing ice to form, bacteria there have had their DNA mutated to survive the ultra-violet radiation and low oxygen levels. Such a habitat might well be similar to primitive Earth. Outside the six major elements essential for life: carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur, even toxic arsenic might be used by some organisms as in close proximity to phosphorus. A NASA team, by early 2017, discovered within the Mexican giant crystal-cave of Naica, micro-organisms which evolved in a ancient past to nurture upon sulfites, manganese or copper oxyde. Before, 500,000 years old microbes and still alive had been found trapped into water ice and salt, a more life-prone environment still. Follow the trace of heat and water? Underground hydrothermal sources at Mars, comets or some asteroids might be hence the best candidates in the solar system! Even very low access to any nutrients don't prohibit the existence of life, like seen at Earth at undersea spots the most devoided of any possibility of nurture except the radioactive decay of the seafloor, which splits water into its hydrogen and oxygen atoms. Such process might work too in wet sediments at Mars or Europa. Best analog to such environment might be a briny, subsurface lake in Antarctica, by 65 feet underneath which harbors a variety of bacteria. With no oxygen, mostly frozen and with strong nitrous oxide levels, six times saltier than seawater, and a temperature of minus 8°. F., that environment has been isolated from outside influences for more than 3,000 years. Reactions between the brine and the underlying iron-rich sediments generate nitrous oxide and molecular hydrogen might in part provide the energy needed microbial life. Recent findings further, by 2010, further are showing that life under the advanced form of shrimps, seems too to be found 600 ft under the Antarctic icesheets with subfreezing temperatures and dark waters, which could be a hint to such environments like the buried oceans of Europa or maybe Enceladus. That adaptibility of life, further, is hinting to what life might have looked like when the first two varieties of atmosphere at the Earth were lacking of any oxygen. Plate tectonics, generally, would be a factor too to life, generating changing and varied environmental conditions

NASA mostly now is leaning to the wiev that Earth-life biochemistry is not universal, even in terms of how DNA is manufactured, with basic compounds different from the phosphorous, carbon, etc. used at Earth which might change the traces NASA missions are looking for on alien moons or planets. Such exotic life forms might also make a 'shadow biosphere' on Earth self, with a radically different DNA structure. Modifications could also hold to the nature of the Sun around which life is extant. Plants living around a red dwarf would have, for example, to gather more light and likely be much darker or even black due to the logics of photosynthesis. In the case of a dual star-system, plants would either adapt to gather light from both or, more likely, two categories of plants would appear, one linked to each of both sun. A UV radiation barrage to the early Earth, on the other hand, with levels exceeding those observed on some of the potentially habitable planets did not hinder life to appear after that

How Life Appeared and Worked at Earth

->Life at Earth Early
Scientists know that the earliest Earth was cold enough to bear oceans and continents due to two, less than two human hairs in diameter tiny grains of zircon crystal which date back to when the Earth was 4.4 billion years old. These are the oldest rocks found relative to Earth's history. They are an evidence for that the Earth was apt to bear life as soon as its very beginnings. The earliest rock before this one was dating back to 3.8 billion years only. The most ancient life trace has been discovered by 2016 in the Greenland, with a microbial form reaching to 3.7 billion years, which is about 200 million years older than the known South African, and Australian traces

The Earth is 4.5 billion years old. Like any other rocky planet in the solar system it formed by accretion of planetesimals, those blocks of icy-rocky materials. Once the primitive Earth reached the size of the Moon such materials melted and then cooled, forming the usual three layers found at any terrestrial planet. A core, a mantle, and a crust. The vast majority of carbon, nitrogen, sulfur, hydrogen and other volatile elements was delivered to Earth at the moment of our Moon's creation through a gigantic impact 4.4 billion years ago. Such that early Earth is provided an atmosphere, and oceans, via the cooling and outgasing process. The atmosphere is different in composition from the atmosphere of today, with nitrogen and hydrogen mostly. Some 4 billion years ago, the Sun shone with only about three-quarters its current brightness as the so-called 'Faint Young Sun Paradox' had the Earth at that time not being a icy ball but a warm globe with liquid water. Such a heat likely was yielded by solar storms and superflares despite Sun's faintness. The Earth's magnetosphere at the time furter was weaker with a wider footprint near the poles as the atmosphere of mostly, at 9O percent, molecular nitrogen. A series of interaction between the solar wind and the nitrogen in the atmosphere eventually turned nitrous oxide, a greenhouse gas 300 more powerful that carbon dioxide. Such a environment may have done more than just warm the atmosphere and have provided the energy needed to make complex chemicals and eventually basics of life up to the DNA-RNA. Seeding life on early Earth also owed to violent outburst of the young Sun, which ignited chemical reactions that kept Earth warm and wet as such events on other worlds could prevent the emergence of life by stripping them of atmospheres and zapping nourishing chemicals. That is due to that such stars are rotating faster in their infancy than the Sun did. The quicker a young star rotates, the more it destroys conditions for habitability. Lightning further can raise the temperature and pressure of a small portion of the global atmosphere to a very high degree, enabling molecules to form as the process might have helped life arise on Earth. On the Earth nowadays, approximately 100 discharges of lightning occur every second. On the other hand, asteroids and comets quickly come in numbers to hit the planet and they are now known to be bringing too more organic material. This is known as the Heavy Bombardment Period, which lasted 20 to 200 million years, starting since 3.9 billions years ago. One can admit that the Heavy Bombardment Period might have threatened any form of life already present at Earth as those could have taken refuge near the hydrothermal vents at the bottom of the oceans, or deep underneath the Earth -as such events or networks of cracks created, at the same time, by the impacts selves! About 4.1 billion years ago, Earth was pummelled by 4 gigantic impactors and resurfaced, killing off fledgling life. During thay period of time when Earth was constantly bombarded by meteorites and the atmosphere was likely more hydrogen-rich, extraterrestrial compounds were found in meteorites resembling hydrogenases, which are enzymes that provide energy to bacteria and archaea by breaking down hydrogen gas before life began. Meteorite bombardment on ancient Earth may have assisted the origin of life with a supply of life's building blocks, which were produced inside parent-asteroids. Cyanide, a carbon atom bound to a nitrogen atom, is thought to be crucial for the origin of life, as it is involved in the non-biological synthesis of organic compounds like amino acids and nucleobases. Cyanide, along with carbon monoxide (CO), were binding with iron to form stable compounds in the meteorites. Life, thus, at the early Earth, could have started multiple times, or existed in rocks more than 3,000 feet below the oceans. A experiment also evidenced that asteroidal bodies rich in iron impacting a Earth featuring water of the oceans, carbon and nitrogen with a force of 6,000 times the atmospheric pressure naturally yielded amino acids due to the impact. 25 percent of the current Earth's crust were destroyed at the time only. Technically the common ancestor to all living beings is 'LUCA,' the 'Last Universal Common Ancestor', a organism which lived 4 billion years ago. It likely was a heat-loving microbe feeding upon hydrogen gas in a environement devoided of any oxygen with the most likely candidate environment being hydrothermal vents at the bottom of the oceans. Life might well have appeared as soon as 4.4 billion years ago, when the first oceans had formed. Thus only hyperthermophilic, or 'heat-loving,' organisms either could have survived, or being born through the impacts of the asteroids and comets. Such processes might have occur too on the other planets of the solar system. First cellular life is thought to have appeared as soon as the first Earth's crust solidified. First beings Earth are bacteriae able to live upon hydrogen, sulfates, or methane, deep into terrestrial crust or inside primordial oceans, around thermal vents. Bacterial ecosystems have been found living from serpentinization, a process through which crustal rocks in the depth of oceans, called peridotits, unstable in the presence of sea water and hydrating, likely the most populous current microbial life on the Earth! As the Sun was shining less brightly 4.5 billion years ago, when the solar system formed, it's likely that the early Earth was cooler than today and life could develop only due -among others through the existence of liquid water- to that greenhouse gases like methane and carbon dioxide increased the surface temperature through a beneficial greenhouse effect. Varied types of microbes can live on the temperature range of between 32° and 248° F. (0-120° C.) as complex life usually is observed at a range of 32° to 86° F. (0-30° C.). Oldest Earth fossiles, of microbes, dating back to 3.4 billion years ago are the surest evidence of life at Earth, as those lived upon without oxygen and sulfur instead! Earth at that epoch endured a strong volcanism and was hot, as temperatures in the oceans selves reached about 40-50°C. Such a discovery might have implications about what remains of ancient life to find at Mars. No earlier sign of Earthly life exists before 3.5 billion year, with evidence of ancient bacteria found in sedimentary rocks in northwestern Australia. Clays, little by little, stabilized when first sedimentary rocks formed, are key minerals for the development of life because they are not toxic as they have a great capacity of retaining water. After an evolution of about 2.2 billion years, as oxygen-based cells have appeared and Earth's atmosphere have been modified, first multi-cellular lifeforms appear. Cyanobacteria, which are single-celled, prokaryotic, complex cyanobacteria were the author, about 3 billion years ago, that a significant part of the Earth's atmosphere turned oxygen as such organisms gain their energy from sunlight through photosynthesis. Oxygen is a byproduct of that process. The oxygen-ladden atmosphere in turn allowed for higher forms of life to appear, of which multi-celled organisms,or eukaryotic life, Cyanobacteria grew on beach sand as microbial wide, thin layers composed of trillions of individuals. Algae remained the only life at Earth. Life is vegetal and marine only during a further 1.2 billion years when evolutionary pressure has the first animals appear. The "invertebrates" comprise worms, molluscs, and athropods. Although becoming animal, life still remain marine only during 300 million years. At that time, 400 million years ago, life jumps on land. Vegetation expands and leads to a new plant-eating fauna, the "vertebrates", like the fishes, the reptiles or the dinosaurs. The evolutionary process eventually leads to mankind, beginning 8 million years ago. Any living being on Earth, further, holds in its cells a 24-hour, circadian clock since ancient forms of life 1 billion years ago, with a link, or not, to DNA and gene activity. Microbial life generally likely transformed a rocky Earth into the thriving, diverse, life-sustaining planet we inhabit today. Exobiology scientists at NASA Ames are conducting astrobiology research into the origin and early evolution of life, the potential of life to adapt to different environments, and the implications for life elsewhere. Goals of this research are to determine the nature of the most primitive organisms and the environments in which they evolved, and how those microbes and environments have changed over time to produce our world. This requires an investigation of the evolution of genes, metabolic pathways, and microbial species, subject to long-term environmental change. Such an investigation will show the co-evolution of, and interactions within, microbial communities that drive the major recycling processes on Earth as it is also well showing how 'biotechnologies' likely were naturally at work in the past. The tree of life on Earth eventually turned composed with animals, plants, fungi, algae and protists (which are poor known single-celled organisms)

->The Meteors and Any Object Falling Earth and on The Planets, a Factor to Bringing Life
From the asteroids of the Heavy Bombardment to the daily falling tons of meteorites, the Earth, or any planet was -and is- thus provided with deuterium or oxygen-rich polycyclic aromatic hydrocarbons (PAHs), or carbon molecules. Those molecules originated and originate into supernovae events as the harsh conditions of the interstellar space, especially the ultraviolet radiations, attached deuterium (which is heavy hydrogen) or oxygen to then. Those 'quinones', like those particules with those compounds attached are called, are the most common elements to any form of life, hinting again to that those varied objects which falled unto the planets in their early stages, or still now, are well bringing essential elements to the formation of life!

->The Panspermia Theory
The theory of 'panspermia' is a theory among exobiologists, which speculates that life in the solar system, wherever it can resides, might have carried away from one planet to another, or carried for farther out, from the confines of the solar system aboard comets or meteorites. In the case of planets, meteorites, when hitting the surface are ejecting material up into space, possibly with life elements aboard. Comets are thought to transport the ingredients for amino acids, the basic bricks of life, for example. Some extremophiles are able to survive in the even more hostile environment of outer space. Lithopanspermia is a theory according to which rocks ejected from a planet by impact with, say, a meteor, carry organisms on their surface through space and then land those on another planet. Spore-forming organisms might survive more easily. Surviving spores might have higher concentrations of proteins associated with UV radiation resistance

->It's now thought that the moment of the increase of oxygen into the Earth's atmosphere, known like the 'Great Oxidation Event' occurred between 2.3 and 2.4 billion years ago. It might further that, as the beginning of the creation of oxygen be initiated by the ancient ancestors of today's plants by photosynthesis 50 to 100 million years before the event, as the rise of oxygen itself ultimately was controlled by geological processes, like a iron mineral called green rust which took nickel out of oceans, depriving methane-producing microbes as less methane in turn meant less carbon dioxyde and more oxygen accumulation in the Earth's atmosphere

->Life is Left-Handed
Life uses 20 different amino acids in a huge variety of arrangements to build millions of different proteins, those workhorses of life. They come in two non-superimposable forms — left-handed and right-handed — only abiotic or non-biological organic compounds use both. The amino acids that give rise to life must have the same orientation or 'chirality,' which means they use only one of the two available mirror images of the amino-acid structure. Life on Earth got established with only the left-handed version, leading scientists to wonder whether this inclination arose because of random processes or whether meteorites may have seeded this propensity as studies have shown that left-handed amino acids got their start in space, where conditions in asteroids favored the creation of this particular orientation. The question now is whether the bias exists too on other solar system bodies, and if so, does it favor left- or right-handed amino acids. During their journey on top of meteorites or asteroids, or in the primitive protoplanetery disk which gave birth to the solar system, amino acids would have been exposed to the circularly polarized light of neutron stars, or the polarized ultraviolet radiation in the protoplanetary disk or other types of radiation from nearby stars. Such a light is right-handed polarized when out of one pole of the star, and the opposite at the other pole. The right-handed light preferentially breaks apart more of the right-handed amino-acids as the molecular structure of those better absorb the energy of light. As the water ice bearing the acids eventually dryied up, they crystallized leaving behind left-handed amino-acids only because right and left handed pair together, just lefting a surplus of left-handed. More of right-handed version would lie in crystallized form however. Studies in 2012 have shown that non-biological processes in a asteroid could manufacture amino acids, like from a small initial left-hand excess could become greatly amplified at the expense of the opposite-handed amino acids, with some of those even tending to par. Life works with right-handed sugars bringing to a a property important for molecular recognition processes and thought to be a prerequisite for life. The chemistry of life also prefers lighter isotopes, or versions of elements. In laboratory, on a other hand, methods of synthetically creating amino acids result in equal mixtures of left- and right-handed amino acids. A hindrance to exploration will likely be that conditions on exo-worlds might result into the erasement of life evidence, like it might be the case at Mars. Strong oxidizing conditions found on the Red Planet by the Viking missions in 1976 might wipe off any trace of life after a lapse of time

->More About Meteorites Born Left-Handed Amino Acids
Late research by early 2011 have found a excess of the left-handed amino acid isovaline (L-isovaline) in carbon-rich, type 1 (CM1 and CR1) meteorites and that prevalence to be much more common than previously thought. It looks like that occurrence had to be tracked with the history of hot water on asteroids from which those meteorites had been born. The production of isovaline has been seen due to a water-alteration process working when the amino-acid is about used up or destroyed and left in small quantities only. The process further likely amplifies a small existing left-handed amino acid excess and does not create the bias as something in the pre-solar nebula created a small initial bias toward L-isovaline and presumably many other left-handed amino acids as well. That might have been due to radiation from massive stars, neutron stars, or black holes. As far as our solar system is concerned, it is possible that the radiation encountered made left-handed amino acids slightly more likely to be created, or right-handed amino acids a bit more likely to be destroyed. It is also possible, on a other hand, that other, exosolar systems had encountered different radiation favoring right-handed amino acids, for exemple, with potential life there with a bias toward right-handed amino acids instead

Life is Clever and Linked To the Environment

From what is seen at Earth life is clever. Various forms of life may collaborate to yield new forms of bacteriae or cells, or to work and live in a same environment. Life is intimately linked to the environment. It's a tremendous thought to see how the first very simple bacteriae were able to modify the primordial atmosphere on one hand, and, on the other hand, to be possibly damaged or limited by such changes. Further, plants and animals are deeply rooted into their ecosystems and may also be affected by discrete cataclysmic events like meteors impacts. Such a relation with the medium is yielding an evolutionary pressure on lifeforms as some species are thriving on the excesses some others are producing on their environment

->Darwinism is Bushy!
As marine amoeba-shaped creatures called 'Placozoans' might be the most simple creatures on Earth and thus the 'original' animal from what anything living else started, scientists think however that all a variety of corals, jellyfish, sponges, comb jellies and those Placozoans evolved in paralel to 'higher', following animals. A 'bush' model of life thus remains likely the best one to describe the first lineaments of how life began to evolve from the simplest creatures found in the seas. This bodes well with a common idea among life specialists that, contrary to a caricatural Darwinist stance, many evolutionary traits (like a nervous system, or the eye, for example) arose from varied, different processes. Darwin evolution is not linear, but bushing instead!

->The Life More Bizarre Still Than Imagined!
Life, due to its abitlity to thrieve in varied environments, might exist in water, or in liquid nitrogen, or methane as in extremely low, or high acidic environment. Such renewed biochemestry might have led, on the other hand, that such unusual forms of life had appeared even on the Earth at some time, or in some places, and be present still as our techniques of investigation not able to spot those. Another hint to that life might be working differently lies in that a team of scientists, for example, has managed to device artificial DNA chemical nucleotids, as the natural building blocks of the DNA are A, C, T and G nucleotids pairing up and bonding into predictable ways to form the double helix structure of the DNA. Such 'letters' are triggered into a process of replicating are then having the process self-sustaining. As the human genome's DNA is including 3 billion base pairs of the four letters, the artificial molecules are 81 base pairs long only. This is hinting too to that life might really work, even at the DNA level, based on completely different processes than the form of life we're accustomed too

NASA funds an Astrobiology Institute, which partners with hundreds of researchers to search for exo-life. Life is agressively searched too by NASA in our solar system at places like Mars, Titan, the main Saturn's moon, or the icy moons of Jupiter. On the other hand next generation tools like the James Webb Space Telescope (JWST) which will reach the early Universe, improved terrestrial optical techniques, and dedicated space missions like the Terrestrial Planet Finder (TPF) will push the search one step beyond. The light of exoplanets -gas giants like terrestrial planets- will be searched for the ingredients of life at surface or in the atmosphere. The TPF will search terrestrial planets around 150 stars in our immediate stellar environment, about 50 light-years from Earth. "Origins" is a good NASA site about life search beyond the solar system. The famous Drake equation which ponders the diverse factors for advanced civilizations in our Galaxy brings to this estimation of 1 million of them in the Milky Way, that is one each 150 light-years! That is the estimation made through the equation by astronomer Carl Sagan. Science fiction writer Isaac Asimov calculated 670,000 as Drake himself estimated a more conservative 10,000 however. By 1960, NASA already had established an exobiology program, whose early managers adopted an approach to advancing this field of study by funding forward-thinking, boundary-bending, multidisciplinary research projects. After the Viking mission at Mars by 1980, by the 1980s, NASA expanded its exobiology program to encompass studies of evolutionary biology. In the 1990s, NASA again expanded the breadth and depth of this program, broadening the boundaries of “exobiology” to establish “astrobiology” as a program encompassing studies of chemical evolution in interstellar space, the formation and evolution of planets, and the natural history of Earth in addition to exobiology and evolutionary biology. Today NASA’s Astrobiology Program addresses three fundamental questions: How does life begin and evolve? Is there life beyond Earth and, if so, how can we detect it? What is the future of life on Earth and in the universe? Answering these questions brings to improve understanding of biological, planetary and cosmic phenomena and relationships among them in a range of relevant disciplines