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Astrobiology

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"Exobiology" redirects here. Not to be confused with Bioastronautics or Xenobiology.
"Xenology" redirects here. For other uses, see Xenology (disambiguation).

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Nucleic acids may not be the only biomolecules in the universe capable of coding for life processes.[1]

Astrobiology (also xenology or exobiology) is a scientific field within the life and environmental sciences that studies the origins, early evolution, distribution, and future of life in the universe by investigating its deterministic conditions and contingent events.[2] As a discipline, astrobiology is founded on the premise that life may exist beyond Earth.[3]

Research in astrobiology comprises three main areas: the study of habitable environments in the Solar System and beyond, the search for planetary biosignatures of past or present extraterrestrial life, and the study of the origin and early evolution of life on Earth.

The field of astrobiology has its origins in the 20th century with the advent of space exploration and the discovery of exoplanets. Early astrobiology research focused on the search for extraterrestrial life and the study of the potential for life to exist on other planets.[2] In the 1960s and 1970s, NASA began its astrobiology pursuits within the Viking program, which was the first US mission to land on Mars and search for signs of life.[4] This mission, along with other early space exploration missions, laid the foundation for the development of astrobiology as a discipline.

Regarding habitable environments, astrobiology investigates potential locations beyond Earth that could support life, such as Mars, Europa, and exoplanets, through research into the extremophiles populating austere environments on Earth, like volcanic and deep sea environments. Research within this topic is conducted utilising the methodology of the geosciences, especially geobiology, for astrobiological applications.

The search for biosignatures involves the identification of signs of past or present life in the form of organic compounds, isotopic ratios, or microbial fossils. Research within this topic is conducted utilising the methodology of planetary and environmental science, especially atmospheric science, for astrobiological applications, and is often conducted through remote sensing and in situ missions.

Astrobiology also concerns the study of the origin and early evolution of life on Earth to try to understand the conditions that are necessary for life to form on other planets.[5] This research seeks to understand how life emerged from non-living matter and how it evolved to become the diverse array of organisms we see today. Research within this topic is conducted utilising the methodology of paleosciences, especially paleobiology, for astrobiological applications.

Astrobiology is a rapidly developing field with a strong interdisciplinary aspect that holds many challenges and opportunities for scientists. Astrobiology programs and research centres are present in many universities and research institutions around the world, and space agencies like NASA and ESA have dedicated departments and programs for astrobiology research.

Overview

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The term astrobiology was first proposed by the Russian astronomer Gavriil Tikhov in 1953.[6] It is etymologically derived from the Greek ἄστρον, "star"; βίος, "life"; and -λογία, -logia, "study". A close synonym is exobiology from the Greek Έξω, "external"; βίος, "life"; and -λογία, -logia, "study", coined by American molecular biologist Joshua Lederberg; exobiology is considered to have a narrow scope limited to search of life external to Earth.[7] Another associated term is xenobiology, from the Greek ξένος, "foreign"; βίος, "life"; and -λογία, "study", coined by American science fiction writer Robert Heinlein in his work The Star Beast;[8] xenobiology is now used in a more specialised sense, referring to 'biology based on foreign chemistry', whether of extraterrestrial or terrestrial (typically synthetic) origin.[9]

While the potential for extraterrestrial life, especially intelligent life, has been explored throughout human history within philosophy and narrative, the question is a verifiable hypothesis and thus a valid line of scientific inquiry;[10][11] planetary scientist David Grinspoon calls it a field of natural philosophy, grounding speculation on the unknown in known scientific theory.[12]

The modern field of astrobiology can be traced back to the 1950s and 1960s with the advent of space exploration, when scientists began to seriously consider the possibility of life on other planets. In 1957, the Soviet Union launched Sputnik 1, the first artificial satellite, which marked the beginning of the Space Age. This event led to an increase in the study of the potential for life on other planets, as scientists began to consider the possibilities opened up by the new technology of space exploration. In 1959, NASA funded its first exobiology project, and in 1960, NASA founded the Exobiology Program, now one of four main elements of NASA's current Astrobiology Program.[13] In 1971, NASA funded Project Cyclops,[14] part of the search for extraterrestrial intelligence, to search radio frequencies of the electromagnetic spectrum for interstellar communications transmitted by extraterrestrial life outside the Solar System. In the 1960s-1970s, NASA established the Viking program, which was the first US mission to land on Mars and search for metabolic signs of present life; the results were inconclusive.

In the 1980s and 1990s, the field began to expand and diversify as new discoveries and technologies emerged. The discovery of microbial life in extreme environments on Earth, such as deep-sea hydrothermal vents, helped to clarify the feasibility of potential life existing in harsh conditions. The development of new techniques for the detection of biosignatures, such as the use of stable isotopes, also played a significant role in the evolution of the field.

The contemporary landscape of astrobiology emerged in the early 21st century, focused on utilising Earth and environmental science for applications within comparate space environments. Missions included the ESA's Beagle 2, which failed minutes after landing on Mars, NASA's Phoenix lander, which probed the environment for past and present planetary habitability of microbial life on Mars and researched the history of water, and NASA's Curiosity rover, currently probing the environment for past and present planetary habitability of microbial life on Mars.

Theoretical foundations

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Planetary habitability

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Main article: Planetary habitability

Astrobiological research makes a number of simplifying assumptions when studying the necessary components for planetary habitability.

Carbon and Organic Compounds: Carbon is the fourth most abundant element in the universe and the energy required to make or break a bond is at just the appropriate level for building molecules which are not only stable, but also reactive. The fact that carbon atoms bond readily to other carbon atoms allows for the building of extremely long and complex molecules. As such, astrobiological research presumes that the vast majority of life forms in the Milky Way galaxy are based on carbon chemistries, as are all life forms on Earth.[15][16] However, theoretical astrobiology entertains the potential for other organic molecular bases for life, thus astrobiological research often focuses on identifying environments that have the potential to support life based on the presence of organic compounds.

Liquid water: Liquid water is a common molecule that provides an excellent environment for the formation of complicated carbon-based molecules, and is generally considered necessary for life as we know it to exist. Thus, astrobiological research presumes that extraterrestrial life similarly depends upon access to liquid water, and often focuses on identifying environments that have the potential to support liquid water.[17][18] Some researchers posit environments of water-ammonia mixtures as possible solvents for hypothetical types of biochemistry.[19]

Environmental stability: Where organisms adaptively evolve to the conditions of the environments in which they reside, environmental stability is considered necessary for life to exist. This presupposes the necessity of a stable temperature, pressure, and radiation levels; resultantly, astrobiological research focuses on planets orbiting Sun-like red dwarf stars.[20][16] This is because very large stars have relatively short lifetimes, meaning that life might not have time to emerge on planets orbiting them; very small stars provide so little heat and warmth that only planets in very close orbits around them would not be frozen solid, and in such close orbits these planets would be tidally locked to the star;[21] whereas the long lifetimes of red dwarfs could allow the development of habitable environments on planets with thick atmospheres.[22] This is significant as red dwarfs are extremely common. (See also: Habitability of red dwarf systems).

Energy source: It is assumed that any life elsewhere in the universe would also require an energy source. Previously, it was assumed that this would necessarily be from a sun-like star, however with developments within extremophile research contemporary astrobiological research often focuses on identifying environments that have the potential to support life based on the availability of an energy source, such as the presence of volcanic activity on a planet or moon that could provide a source of heat and energy.

It is important to note that these assumptions are based on our current understanding of life on Earth and the conditions under which it can exist. As our understanding of life and the potential for it to exist in different environments evolves, these assumptions may change.

Methods

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Studying terrestrial extremophiles

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Astrobiological research concerning the study of habitable environments in our solar system and beyond utilises methods within the geosciences. Research within this branch primarily concerns the geobiology of organisms that can survive in extreme environments on Earth, such as in volcanic or deep sea environments, to understand the limits of life, and the conditions under which life might be able to survive on other planets. This includes, but is not limited to:

Deep-sea extremophiles: Researchers are studying organisms that live in the extreme environments of deep-sea hydrothermal vents and cold seeps.[23] These organisms survive in the absence of sunlight, and some are able to survive in high temperatures and pressures, and use chemical energy instead of sunlight to produce food.

Desert extremophiles: Researchers are studying organisms that can survive in extreme dry, high temperature conditions, such as in deserts.[24]

Microbes in extreme environments: Researchers are investigating the diversity and activity of microorganisms in environments such as deep mines, subsurface soil, cold glaciers[25] and polar ice,[26] and high-altitude environments.

Researching Earth's present environment

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Research also regards the long-term survival of life on Earth, and the possibilities and hazards of life on other planets, including:

Biodiversity and ecosystem resilience: Scientists are studying how the diversity of life and the interactions between different species contribute to the resilience of ecosystems and their ability to recover from disturbances.[27]

Climate change and extinction: Researchers are investigating the impacts of climate change on different species and ecosystems, and how they may lead to extinction or adaptation.[28] This includes the evolution of Earth's climate and geology, and their potential impact on the habitability of the planet in the future, especially for humans.

Human impact on the biosphere: Scientists are studying the ways in which human activities, such as deforestation, pollution, and the introduction of invasive species, are affecting the biosphere and the long-term survival of life on Earth.[29]

Long-term preservation of life: Researchers are exploring ways to preserve samples of life on Earth for long periods of time, such as cryopreservation and genomic preservation, in the event of a catastrophic event that could wipe out most of life on Earth.[30]

Finding biosignatures on other worlds

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Emerging astrobiological research concerning the search for planetary biosignatures of past or present extraterrestrial life utilise methodologies within planetary sciences. These include:

Main article: Geology of solar terrestrial planets

The study of microbial life in the subsurface of Mars:

Main article: Life on Mars

Scientists are using data from Mars rover missions to study the composition of the subsurface of Mars, searching for biosignatures of past or present microbial life.[31] The study of liquid bodies on icy moons:

Main articles: Life on Europa, life on Titan, and Enceladus § Exploration

Discoveries of surface and subsurface bodies of liquid on moons such as Europa,[32][33][34] Titan[35] and Enceladus[36][37] showed possible habitability zones, making them viable targets for the search for extraterrestrial life. As of September 2024, missions like Europa Clipper and Dragonfly are planned to search for biosignatures within these environments.

The interior of Europa

The study of the atmospheres of planets:

Main article: Life on Venus

Scientists are studying the potential for life to exist in the atmospheres of planets, with a focus on the study of the physical and chemical conditions necessary for such life to exist, namely the detection of organic molecules and biosignature gases; for example, the study of the possibility of life in the atmospheres of exoplanets that orbit red dwarfs and the study of the potential for microbial life in the upper atmosphere of Venus.[38]

Telescopes and remote sensing of exoplanets: The discovery of thousands of exoplanets has opened up new opportunities for the search for biosignatures. Scientists are using telescopes such as the James Webb Space Telescope and the Transiting Exoplanet Survey Satellite to search for biosignatures on exoplanets. They are also developing new techniques for the detection of biosignatures, such as the use of remote sensing to search for biosignatures in the atmosphere of exoplanets.[39]

Talking to extraterrestrials

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SETI and CETI:

Main article: Communication with extraterrestrial intelligence

Scientists search for signals from intelligent extraterrestrial civilizations using radio and optical telescopes within the discipline of extraterrestrial intelligence communications (CETI). CETI focuses on composing and deciphering messages that could theoretically be understood by another technological civilization. Communication attempts by humans have included broadcasting mathematical languages, pictorial systems such as the Arecibo message, and computational approaches to detecting and deciphering 'natural' language communication. While some high-profile scientists, such as Carl Sagan, have advocated the transmission of messages,[40][41] theoretical physicist Stephen Hawking warned against it, suggesting that aliens may raid Earth for its resources.[42]

Investigating the early Earth

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Emerging astrobiological research concerning the study of the origin and early evolution of life on Earth utilises methodologies within the palaeosciences. These include:

The study of the early atmosphere: Researchers are investigating the role of the early atmosphere in providing the right conditions for the emergence of life, such as the presence of gases that could have helped to stabilise the climate and the formation of organic molecules.[43]

The study of the early magnetic field: Researchers are investigating the role of the early magnetic field in protecting the Earth from harmful radiation and helping to stabilise the climate.[44] This research has immense astrobiological implications where the subjects of current astrobiological research like Mars lack such a field.

The study of prebiotic chemistry: Scientists are studying the chemical reactions that could have occurred on the early Earth that led to the formation of the building blocks of life- amino acids, nucleotides, and lipids- and how these molecules could have formed spontaneously under early Earth conditions.[45]

Chart showing the theorized origin of the chemical elements that make up the human body

The study of impact events: Scientists are investigating the potential role of impact events- especially meteorites- in the delivery of water and organic molecules to early Earth.[46]

The study of the primordial soup:

Main article: Primordial soup

Researchers are investigating the conditions and ingredients that were present on the early Earth that could have led to the formation of the first living organisms, such as the presence of water and organic molecules, and how these ingredients could have led to the formation of the first living organisms.[47] This includes the role of water in the formation of the first cells and in catalysing chemical reactions.

The study of the role of minerals: Scientists are investigating the role of minerals like clay in catalysing the formation of organic molecules, thus playing a role in the emergence of life on Earth.[48]

The study of the role of energy and electricity: Scientists are investigating the potential sources of energy and electricity that could have been available on the early Earth, and their role in the formation of organic molecules, thus the emergence of life.[49]

The study of the early oceans: Scientists are investigating the composition and chemistry of the early oceans and how it may have played a role in the emergence of life, such as the presence of dissolved minerals that could have helped to catalyse the formation of organic molecules.[50]

The study of hydrothermal vents: Scientists are investigating the potential role of hydrothermal vents in the origin of life, as these environments may have provided the energy and chemical building blocks needed for its emergence.[51]

The study of plate tectonics: Scientists are investigating the role of plate tectonics in creating a diverse range of environments on the early Earth.[52]

The study of the early biosphere: Researchers are investigating the diversity and activity of microorganisms in the early Earth, and how these organisms may have played a role in the emergence of life.[53]

The study of microbial fossils: Scientists are investigating the presence of microbial fossils in ancient rocks, which can provide clues about the early evolution of life on Earth and the emergence of the first organisms.[54]

Research

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See also: Extraterrestrial life

The systematic search for possible life outside Earth is a valid multidisciplinary scientific endeavor.[55] However, hypotheses and predictions as to its existence and origin vary widely, and at the present, the development of hypotheses firmly grounded on science may be considered astrobiology's most concrete practical application. It has been proposed that viruses are likely to be encountered on other life-bearing planets,[56][57] and may be present even if there are no biological cells.[58]

Research outcomes

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As of 2024, no evidence of extraterrestrial life has been identified.[59] Examination of the Allan Hills 84001 meteorite, which was recovered in Antarctica in 1984 and originated from Mars, is thought by David McKay, as well as few other scientists, to contain microfossils of extraterrestrial origin; this interpretation is controversial.[60][61][62]

Asteroid(s) may have transported life to Earth.

Yamato 000593, the second largest meteorite from Mars, was found on Earth in 2000. At a microscopic level, spheres are found in the meteorite that are rich in carbon compared to surrounding areas that lack such spheres. The carbon-rich spheres may have been formed by biotic activity according to some NASA scientists.[63][64][65]

On 5 March 2011, Richard B. Hoover, a scientist with the Marshall Space Flight Center, speculated on the finding of alleged microfossils similar to cyanobacteria in CI1 carbonaceous meteorites in the fringe Journal of Cosmology, a story widely reported on by mainstream media.[66][67] However, NASA formally distanced itself from Hoover's claim.[68] According to American astrophysicist Neil deGrasse Tyson: "At the moment, life on Earth is the only known life in the universe, but there are compelling arguments to suggest we are not alone."[69]

Elements of astrobiology

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Astronomy

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Main article: Astronomy
Artist's impression of the extrasolar planet OGLE-2005-BLG-390Lb orbiting its star 20,000 light-years from Earth; this planet was discovered with gravitational microlensing.
The NASA Kepler mission, launched in March 2009, searches for extrasolar planets.

Most astronomy-related astrobiology research falls into the category of extrasolar planet (exoplanet) detection, the hypothesis being that if life arose on Earth, then it could also arise on other planets with similar characteristics. To that end, a number of instruments designed to detect Earth-sized exoplanets have been considered, most notably NASA's Terrestrial Planet Finder (TPF) and ESA's Darwin programs, both of which have been cancelled. NASA launched the Kepler mission in March 2009, and the French Space Agency launched the COROT space mission in 2006.[70][71] There are also several less ambitious ground-based efforts underway.

The goal of these missions is not only to detect Earth-sized planets but also to directly detect light from the planet so that it may be studied spectroscopically. By examining planetary spectra, it would be possible to determine the basic composition of an extrasolar planet's atmosphere and/or surface.[72] Given this knowledge, it may be possible to assess the likelihood of life being found on that planet. A NASA research group, the Virtual Planet Laboratory,[73] is using computer modeling to generate a wide variety of virtual planets to see what they would look like if viewed by TPF or Darwin. It is hoped that once these missions come online, their spectra can be cross-checked with these virtual planetary spectra for features that might indicate the presence of life.

An estimate for the number of planets with intelligent communicative extraterrestrial life can be gleaned from the Drake equation, essentially an equation expressing the probability of intelligent life as the product of factors such as the fraction of planets that might be habitable and the fraction of planets on which life might arise:[74]

where:

  • N = The number of communicative civilizations
  • R* = The rate of formation of suitable stars (stars such as the Sun)
  • fp = The fraction of those stars with planets (current evidence indicates that planetary systems may be common for stars like the Sun)
  • ne = The number of Earth-sized worlds per planetary system
  • fl = The fraction of those Earth-sized planets where life actually develops
  • fi = The fraction of life sites where intelligence develops
  • fc = The fraction of communicative planets (those on which electromagnetic communications technology develops)
  • L = The "lifetime" of communicating civilizations

However, whilst the rationale behind the equation is sound, it is unlikely that the equation will be constrained to reasonable limits of error any time soon. The problem with the formula is that it is not used to generate or support hypotheses because it contains factors that can never be verified. The first term, R*, number of stars, is generally constrained within a few orders of magnitude. The second and third terms, fp, stars with planets and fe, planets with habitable conditions, are being evaluated for the star's neighborhood. Drake originally formulated the equation merely as an agenda for discussion at the Green Bank conference,[75] but some applications of the formula had been taken literally and related to simplistic or pseudoscientific arguments.[76] Another associated topic is the Fermi paradox, which suggests that if intelligent life is common in the universe, then there should be obvious signs of it.

Another active research area in astrobiology is planetary system formation. It has been suggested that the peculiarities of the Solar System (for example, the presence of Jupiter as a protective shield)[77] may have greatly increased the probability of intelligent life arising on Earth.[78][79]

Biology

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See also: Abiogenesis, Biology, and Extremophile
Hydrothermal vents support extremophile bacteria on Earth, provided an energy-rich environment for the origin of life, and may also support life in other parts of the cosmos.

Biology cannot state that a process or phenomenon, by being mathematically possible, has to exist forcibly in an extraterrestrial body. Biologists specify what is speculative and what is not.[76] The discovery of extremophiles, organisms able to survive in extreme environments, became a core research element for astrobiologists, as they are important to understand four areas in the limits of life in planetary context: the potential for panspermia, forward contamination due to human exploration ventures, planetary colonization by humans, and the exploration of extinct and extant extraterrestrial life.[80]

Until the 1970s, life was thought to be entirely dependent on energy from the Sun. Plants on Earth's surface capture energy from sunlight to photosynthesize sugars from carbon dioxide and water, releasing oxygen in the process that is then consumed by oxygen-respiring organisms, passing their energy up the food chain. Even life in the ocean depths, where sunlight cannot reach, was thought to obtain its nourishment either from consuming organic detritus rained down from the surface waters or from eating animals that did.[81] The world's ability to support life was thought to depend on its access to sunlight. However, in 1977, during an exploratory dive to the Galapagos Rift in the deep-sea exploration submersible Alvin, scientists discovered colonies of giant tube worms, clams, crustaceans, mussels, and other assorted creatures clustered around undersea volcanic features known as black smokers.[81] These creatures thrive despite having no access to sunlight, and it was soon discovered that they form an entirely independent ecosystem. Although most of these multicellular lifeforms need dissolved oxygen (produced by oxygenic photosynthesis) for their aerobic cellular respiration and thus are not completely independent from sunlight by themselves, the basis for their food chain is a form of bacterium that derives its energy from oxidization of reactive chemicals, such as hydrogen or hydrogen sulfide, that bubble up from the Earth's interior. Other lifeforms entirely decoupled from the energy from sunlight are green sulfur bacteria which are capturing geothermal light for anoxygenic photosynthesis or bacteria running chemolithoautotrophy based on the radioactive decay of uranium.[82] This chemosynthesis revolutionized the study of biology and astrobiology by revealing that life need not be sunlight-dependent; it only requires water and an energy gradient in order to exist.

Biologists have found extremophiles that thrive in ice, boiling water, acid, alkali, the water core of nuclear reactors, salt crystals, toxic waste and in a range of other extreme habitats that were previously thought to be inhospitable for life.[83][84] This opened up a new avenue in astrobiology by massively expanding the number of possible extraterrestrial habitats. Characterization of these organisms, their environments and their evolutionary pathways, is considered a crucial component to understanding how life might evolve elsewhere in the universe. For example, some organisms able to withstand exposure to the vacuum and radiation of outer space include the lichen fungi Rhizocarpon geographicum and Rusavskia elegans,[85] the bacterium Bacillus safensis,[86] Deinococcus radiodurans,[86] Bacillus subtilis,[86] yeast Saccharomyces cerevisiae,[86] seeds from Arabidopsis thaliana ('mouse-ear cress'),[86] as well as the invertebrate animal Tardigrade.[86] While tardigrades are not considered true extremophiles, they are considered extremotolerant microorganisms that have contributed to the field of astrobiology. Their extreme radiation tolerance and presence of DNA protection proteins may provide answers as to whether life can survive away from the protection of the Earth's atmosphere.[87]

Jupiter's moon, Europa,[84][88][89][90][91] and Saturn's moon, Enceladus,[92][36] are now considered the most likely locations for extant extraterrestrial life in the Solar System due to their subsurface water oceans where radiogenic and tidal heating enables liquid water to exist.[82]

The origin of life, known as abiogenesis, distinct from the evolution of life, is another ongoing field of research. Oparin and Haldane postulated that the conditions on the early Earth were conducive to the formation of organic compounds from inorganic elements and thus to the formation of many of the chemicals common to all forms of life we see today. The study of this process, known as prebiotic chemistry, has made some progress, but it is still unclear whether or not life could have formed in such a manner on Earth. The alternative hypothesis of panspermia is that the first elements of life may have formed on another planet with even more favorable conditions (or even in interstellar space, asteroids, etc.) and then have been carried over to Earth.

The cosmic dust permeating the universe contains complex organic compounds ("amorphous organic solids with a mixed aromatic-aliphatic structure") that could be created naturally, and rapidly, by stars.[93][94][95] Further, a scientist suggested that these compounds may have been related to the development of life on Earth and said that, "If this is the case, life on Earth may have had an easier time getting started as these organics can serve as basic ingredients for life."[93]

More than 20% of the carbon in the universe may be associated with polycyclic aromatic hydrocarbons (PAHs), possible starting materials for the formation of life. PAHs seem to have been formed shortly after the Big Bang, are widespread throughout the universe, and are associated with new stars and exoplanets.[96] PAHs are subjected to interstellar medium conditions and are transformed through hydrogenation, oxygenation and hydroxylation, to more complex organics—"a step along the path toward amino acids and nucleotides, the raw materials of proteins and DNA, respectively".[97][98]

In October 2020, astronomers proposed the idea of detecting life on distant planets by studying the shadows of trees at certain times of the day to find patterns that could be detected through observation of exoplanets.[99][100]

Philosophy

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David Grinspoon called astrobiology a field of natural philosophy.[101] Astrobiology intersects with philosophy by raising questions about the nature and existence of life beyond Earth. Philosophical implications include the definition of life itself, issues in the philosophy of mind and cognitive science in case intelligent life is found, epistemological questions about the nature of proof, ethical considerations of space exploration, along with the broader impact of discovering extraterrestrial life on human thought and society.

Dunér[102] has emphasized philosophy of astrobiology as an ongoing existential exercise in individual and collective self-understanding, whose major task is constructing and debating concepts such as the concept of life. Key issues, for Dunér, are questions of resource money and monetary planning, epistemological questions regarding astrobiological knowledge, linguistics issues about interstellar communication, cognitive issues such as the definition of intelligence, along with the possibility of interplanetary contamination. Persson[103] also emphasized key philosophical questions in astrobiology. They include ethical justification of resources, the question of life in general, the epistemological issues and knowledge about being alone in the universe, ethics towards extraterrestrial life, the question of politics and governing uninhabited worlds, along with questions of ecology.

For von Hegner,[104] the question of astrobiology and the possibility of astrophilosophy differs. For him, the discipline needs to bifurcate into astrobiology and astrophilosophy since discussions made possible by astrobiology, but which have been astrophilosophical in nature, have existed as long as there have been discussions about extraterrestrial life. Astrobiology is a self-corrective interaction among observation, hypothesis, experiment, and theory, pertaining to the exploration of all natural phenomena. Astrophilosophy consists of methods of dialectic analysis and logical argumentation, pertaining to the clarification of the nature of reality. Šekrst[105] argues that astrobiology requires the affirmation of astrophilosophy, but not as a separate cognate to astrobiology. The stance of conceptual speciesm, according to Šekrst, permeates astrobiology since the very name astrobiology tries to talk about not just biology, but about life in a general way, which includes terrestrial life as a subset. This leads us to either redefine philosophy, or consider the need for astrophilosophy as a more general discipline, to which philosophy is just a subset that deals with questions such as the nature of the human mind and other anthropocentric questions.

Most of the philosophy of astrobiology deals with two main questions: the question of life and the ethics of space exploration. Kolb[106] specifically emphasizes the question of viruses, for which the question whether they are alive or not is based on the definitions of life that include self-replication. Schneider[107] tried to defined exo-life, but concluded that we often start with our own prejudices and that defining extraterrestrial life seems futile using human concepts. For Dick, astrobiology relies on metaphysical assumption that there is extraterrestrial life, which reaffirms questions in the philosophy of cosmology, such as fine-tuning or the anthropic principle.

Rare Earth hypothesis

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Main article: Rare Earth hypothesis

The Rare Earth hypothesis postulates that multicellular life forms found on Earth may actually be more of a rarity than scientists assume. According to this hypothesis, life on Earth (and more, multi-cellular life) is possible because of a conjunction of the right circumstances (galaxy and location within it, planetary system, star, orbit, planetary size, atmosphere, etc.); and the chance for all those circumstances to repeat elsewhere may be rare. It provides a possible answer to the Fermi paradox which suggests, "If extraterrestrial aliens are common, why aren't they obvious?" It is apparently in opposition to the principle of mediocrity, assumed by famed astronomers Frank Drake, Carl Sagan, and others. The principle of mediocrity suggests that life on Earth is not exceptional, and it is more than likely to be found on innumerable other worlds.

Missions

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Research into the environmental limits of life and the workings of extreme ecosystems is ongoing, enabling researchers to better predict what planetary environments might be most likely to harbor life. Missions such as the Phoenix lander, Mars Science Laboratory, ExoMars, Mars 2020 rover to Mars, and the Cassini probe to Saturn's moons aim to further explore the possibilities of life on other planets in the Solar System.

Viking program
Main article: Viking lander biological experiments

The two Viking landers each carried four types of biological experiments to the surface of Mars in the late 1970s. These were the only Mars landers to carry out experiments looking specifically for metabolism by current microbial life on Mars. The landers used a robotic arm to collect soil samples into sealed test containers on the craft. The two landers were identical, so the same tests were carried out at two places on Mars' surface; Viking 1 near the equator and Viking 2 further north.[108] The result was inconclusive,[109] and is still disputed by some scientists.[110][111][112][113]

Norman Horowitz was the chief of the Jet Propulsion Laboratory bioscience section for the Mariner and Viking missions from 1965 to 1976. Horowitz considered that the great versatility of the carbon atom makes it the element most likely to provide solutions, even exotic solutions, to the problems of survival of life on other planets.[114] However, he also considered that the conditions found on Mars were incompatible with carbon based life.

Beagle 2
Replica of the 33.2 kg Beagle-2 lander
Mars Science Laboratory rover concept artwork

Beagle 2 was an unsuccessful British Mars lander that formed part of the European Space Agency's 2003 Mars Express mission. Its primary purpose was to search for signs of life on Mars, past or present. Although it landed safely, it was unable to correctly deploy its solar panels and telecom antenna.[115]

EXPOSE

EXPOSE is a multi-user facility mounted in 2008 outside the International Space Station dedicated to astrobiology.[116][117] EXPOSE was developed by the European Space Agency (ESA) for long-term spaceflights that allow exposure of organic chemicals and biological samples to outer space in low Earth orbit.[118]

Mars Science Laboratory

The Mars Science Laboratory (MSL) mission landed the Curiosity rover that is currently in operation on Mars.[119] It was launched 26 November 2011, and landed at Gale Crater on 6 August 2012. Mission objectives are to help assess Mars' habitability and in doing so, determine whether Mars is or has ever been able to support life,[120] collect data for a future human mission, study Martian geology, its climate, and further assess the role that water, an essential ingredient for life as we know it, played in forming minerals on Mars.

Tanpopo

The Tanpopo mission is an orbital astrobiology experiment investigating the potential interplanetary transfer of life, organic compounds, and possible terrestrial particles in the low Earth orbit. The purpose is to assess the panspermia hypothesis and the possibility of natural interplanetary transport of microbial life as well as prebiotic organic compounds. Early mission results show evidence that some clumps of microorganism can survive for at least one year in space.[121] This may support the idea that clumps greater than 0.5 millimeters of microorganisms could be one way for life to spread from planet to planet.[121]

ExoMars rover
ExoMars rover model

ExoMars is a robotic mission to Mars to search for possible biosignatures of Martian life, past or present. This astrobiological mission was under development by the European Space Agency (ESA) in partnership with the Russian Federal Space Agency (Roscosmos); it was planned for a 2022 launch;[122][123][124] however, technical and funding issues and the Russian invasion of Ukraine have forced ESA to repeatedly delay the rover's delivery to 2028.[125]

Mars 2020
Artist's rendition of the Perseverance rover on Mars, with the mini-helicopter Ingenuity in front

Mars 2020 successfully landed its rover Perseverance in Jezero Crater on 18 February 2021. It will investigate environments on Mars relevant to astrobiology, investigate its surface geological processes and history, including the assessment of its past habitability and potential for preservation of biosignatures and biomolecules within accessible geological materials.[126] The Science Definition Team is proposing the rover collect and package at least 31 samples of rock cores and soil for a later mission to bring back for more definitive analysis in laboratories on Earth. The rover could make measurements and technology demonstrations to help designers of a human expedition understand any hazards posed by Martian dust and demonstrate how to collect carbon dioxide (CO2), which could be a resource for making molecular oxygen (O2) and rocket fuel.[127][128]

Europa Clipper

Europa Clipper is a mission launched by NASA on 14 October 2024 that will conduct detailed reconnaissance of Jupiter's moon Europa beginning in 2030, and will investigate whether its internal ocean could harbor conditions suitable for life.[129][130][131] It will also aid in the selection of future landing sites.[132][133]

Dragonfly

Dragonfly is a NASA mission scheduled to land on Titan in 2036 to assess its microbial habitability and study its prebiotic chemistry. Dragonfly is a rotorcraft lander that will perform controlled flights between multiple locations on the surface, which allows sampling of diverse regions and geological contexts.[134]

Proposed concepts

[edit]
Icebreaker Life

Icebreaker Life is a lander mission that was proposed for NASA's Discovery Program for the 2021 launch opportunity,[135] but it was not selected for development. It would have had a stationary lander that would be a near copy of the successful 2008 Phoenix and it would have carried an upgraded astrobiology scientific payload, including a 1-meter-long core drill to sample ice-cemented ground in the northern plains to conduct a search for organic molecules and evidence of current or past life on Mars.[136][137] One of the key goals of the Icebreaker Life mission is to test the hypothesis that the ice-rich ground in the polar regions has significant concentrations of organics due to protection by the ice from oxidants and radiation.

Journey to Enceladus and Titan

Journey to Enceladus and Titan (JET) is an astrobiology mission concept to assess the habitability potential of Saturn's moons Enceladus and Titan by means of an orbiter.[138][139][140]

Enceladus Life Finder

Enceladus Life Finder (ELF) is a proposed astrobiology mission concept for a space probe intended to assess the habitability of the internal aquatic ocean of Enceladus, Saturn's sixth-largest moon.[141][142]

Life Investigation For Enceladus

Life Investigation For Enceladus (LIFE) is a proposed astrobiology sample-return mission concept. The spacecraft would enter into Saturn orbit and enable multiple flybys through Enceladus' icy plumes to collect icy plume particles and volatiles and return them to Earth on a capsule. The spacecraft may sample Enceladus' plumes, the E ring of Saturn, and the upper atmosphere of Titan.[143][144][145]

Oceanus

Oceanus is an orbiter proposed in 2017 for the New Frontiers mission No. 4. It would travel to the moon of Saturn, Titan, to assess its habitability.[146] Oceanus' objectives are to reveal Titan's organic chemistry, geology, gravity, topography, collect 3D reconnaissance data, catalog the organics and determine where they may interact with liquid water.[147]

Explorer of Enceladus and Titan

Explorer of Enceladus and Titan (E2T) is an orbiter mission concept that would investigate the evolution and habitability of the Saturnian satellites Enceladus and Titan. The mission concept was proposed in 2017 by the European Space Agency.[148]

See also

[edit]

Citations

[edit]
  1. ^ "Launching the Alien Debates (part 1 of 7)". Astrobiology Magazine. NASA. 8 December 2006. Archived from the original on 23 October 2020. Retrieved 5 May 2014.{{cite web}}: CS1 maint: unfit URL (link)
  2. ^ a b "About Astrobiology". NASA Astrobiology Institute. NASA. 21 January 2008. Archived from the original on 11 October 2008. Retrieved 20 October 2008.
  3. ^ "About Astrobiology". NASA Astrobiology Institute. NASA. Retrieved 29 January 2023.
  4. ^ Steven J. Dick & James E. Strick (2004). The Living Universe: NASA and the Development of Astrobiology. New Brunswick, NJ: Rutgers University Press.
  5. ^ "Origins of Life and Evolution of Biospheres". Journal: Origins of Life and Evolution of Biospheres. Retrieved 6 April 2015.
  6. ^ Cockell, Charles S. (2001). "'Astrobiology' and the ethics of new science". Interdisciplinary Science Reviews. 26 (2): 90–96. doi:10.1179/0308018012772533.
  7. ^ Launching a New Science: Exobiology and the Exploration of Space The National Library of Medicine.
  8. ^ Heinlein R, Harold W (21 July 1961). "Xenobiology". Science. 134 (3473): 223–225. Bibcode:1961Sci...134..223H. doi:10.1126/science.134.3473.223. JSTOR 1708323. PMID 17818726.
  9. ^ Markus Schmidt (9 March 2010). "Xenobiology: A new form of life as the ultimate biosafety tool". BioEssays. 32 (4): 322–331. doi:10.1002/bies.200900147. PMC 2909387. PMID 20217844.
  10. ^ Livio, Mario (15 February 2017). "Winston Churchill's essay on alien life found". Nature. 542 (7641): 289–291. Bibcode:2017Natur.542..289L. doi:10.1038/542289a. PMID 28202987. S2CID 205092694.
  11. ^ De Freytas-Tamura, Kimiko (15 February 2017). "Winston Churchill Wrote of Alien Life in a Lost Essay". The New York Times. Archived from the original on 1 January 2022. Retrieved 18 February 2017.
  12. ^ Grinspoon 2004
  13. ^ Hubbard, G. Scott. "Astrobiology: Its Origins and Development". NASA. Archived from the original on 28 June 2022. Retrieved 29 January 2023.
  14. ^ "Project Cyclops: a Design Study of a System for Detecting Extraterrestrial Intelligent Life". NASA. January 1972. Retrieved 29 January 2023.
  15. ^ "Polycyclic Aromatic Hydrocarbons: An Interview With Dr. Farid Salama". Astrobiology Magazine. 2000. Archived from the original on 20 June 2008. Retrieved 20 October 2008.
  16. ^ a b Pace, Norman R. (30 January 2001). "The universal nature of biochemist ry". Proceedings of the National Academy of Sciences of the USA. 98 (3): 805–808. Bibcode:2001PNAS...98..805P. doi:10.1073/pnas.98.3.805. PMC 33372. PMID 11158550.
  17. ^ Astrobiology. Macmillan Science Library: Space Sciences. 2006. Retrieved 20 October 2008.
  18. ^ Camprubi, Eloi; et al. (12 December 2019). "Emergence of Life". Space Science Reviews. 215 (56): 56. Bibcode:2019SSRv..215...56C. doi:10.1007/s11214-019-0624-8.
  19. ^ Penn State (19 August 2006). "The Ammonia-Oxidizing Gene". Astrobiology Magazine. Archived from the original on 4 August 2011. Retrieved 20 October 2008.{{cite web}}: CS1 maint: unfit URL (link)
  20. ^ "Stars and Habitable Planets". Sol Company. 2007. Archived from the original on 1 October 2008. Retrieved 20 October 2008.
  21. ^ "M Dwarfs: The Search for Life is On". Red Orbit & Astrobiology Magazine. 29 August 2005. Retrieved 20 October 2008.[permanent dead link]
  22. ^ Mautner, Michael N. (2005). "Life in the cosmological future: Resources, biomass and populations" (PDF). Journal of the British Interplanetary Society. 58: 167–180. Bibcode:2005JBIS...58..167M. Archived (PDF) from the original on 9 October 2022.
  23. ^ "Life in the Extreme: Hydrothermal Vents". NASA Astrobiology Institute. NASA. Retrieved 29 January 2023.
  24. ^ Merino, Nancy; Aronson, Heidi S.; Bojanova, Diana P.; Feyhl-Buska, Jayme; Wong, Michael L.; Zhang, Shu; Giovannelli, Donato (15 April 2019). "Living at the Extremes: Extremophiles and the Limits of Life in a Planetary Context". Frontiers in Microbiology. 10: 780. Bibcode:2019FrMic..10..780M. doi:10.3389/fmicb.2019.00780. PMC 6476344. PMID 31037068.
  25. ^ Mykytczuk, N. C.; Foote, S. J.; Omelon, C. R.; Southam, G.; Greer, C. W.; Whyte, L. G. (7 February 2013). "Microbial Ecology and Functional Diversity of Natural Habitats". The ISME Journal. 7 (6): 1211–1226. doi:10.1038/ismej.2013.8. PMC 3660685. PMID 23389107.
  26. ^ Cheptsov, V. S.; Vorobyova, E. A.; Polyanskaya, L. M.; Gorlenko, M. V.; Pavlov, A. K.; Lomasov, V. N. (28 September 2018). "Sustainability of Extreme Microbial Ecosystems to the Comprehensive Impact of Physical Factors of the Martian Regolith". Moscow University Soil Science Bulletin. 73 (3): 119–123. Bibcode:2018MUSSB..73..119C. doi:10.3103/S0147687418030043. S2CID 135443326.
  27. ^ "Astrobiology Objectives: Microbial Ecology". Astrobiology at NASA. NASA. Retrieved 29 January 2023.
  28. ^ "Effects of Climate and Geology on Habitability". Astrobiology at NASA. NASA. Retrieved 29 January 2023.
  29. ^ "Earth's Future Habitability". Astrobiology at NASA. NASA. Retrieved 29 January 2023.
  30. ^ "Bringing Life with Us beyond Earth". Astrobiology at NASA. NASA. Retrieved 29 January 2023.
  31. ^ Tarnas, J.D.; Mustard, J.F.; Sherwood Lollar, B.; Stamenković, V.; Cannon, K.M.; Lorand, J.-P.; Onstott, T.C.; Michalski, J.R.; Warr, O.; Palumbo, A.M.; Plesa, A.-C. (11 June 2021). "Earth-like Habitable Environments in the Subsurface of Mars" (PDF). Astrobiology. 21 (6): 741–756. Bibcode:2021AsBio..21..741T. doi:10.1089/ast.2020.2386. PMID 33885329. S2CID 233352375.
  32. ^ Tritt, Charles S. (2002). "Possibility of Life on Europa". Milwaukee School of Engineering. Archived from the original on 9 June 2007. Retrieved 20 October 2008.
  33. ^ Friedman, Louis (14 December 2005). "Projects: Europa Mission Campaign". The Planetary Society. Archived from the original on 20 September 2008. Retrieved 20 October 2008.
  34. ^ David, Leonard (10 November 1999). "Move Over Mars – Europa Needs Equal Billing". Space.com. Retrieved 20 October 2008.
  35. ^ "Life on Titan?". ESA. Retrieved 31 August 2024.
  36. ^ a b Kazan, Casey (2 June 2011). "Saturn's Enceladus Moves to Top of "Most-Likely-to-Have-Life" List". The Daily Galaxy. Retrieved 3 June 2011.
  37. ^ Lovett, Richard A. (31 May 2011). "Enceladus named sweetest spot for alien life". Nature. doi:10.1038/news.2011.337. Retrieved 3 June 2011.
  38. ^ Limaye, Sanjay S.; Mogul, Rakesh; Baines, Kevin H.; Bullock, Mark A.; Cockell, Charles; Cutts, James A.; Gentry, Diana M.; Grinspoon, David H.; Head, James W.; Jessup, Kandis-Lea; Kompanichenko, Vladimir; Lee, Yeon Joo; Mathies, Richard; Milojevic, Tetyana; Pertzborn, Rosalyn A.; Rothschild, Lynn; Sasaki, Satoshi; Schulze-Makuch, Dirk; Smith, David J.; Way, Michael J. (7 October 2021). "Venus, an Astrobiology Target". Astrobiology. 21 (10): 1163–1185. Bibcode:2021AsBio..21.1163L. doi:10.1089/ast.2020.2268. PMID 33970019. S2CID 234344026.
  39. ^ Seager, Sara (4 August 2014). "The future of spectroscopic life detection on exoplanets". PNAS. 111 (35): 12634–12640. Bibcode:2014PNAS..11112634S. doi:10.1073/pnas.1304213111. PMC 4156723. PMID 25092345.
  40. ^ Sagan, Carl. Communication with Extraterrestrial Intelligence. MIT Press, 1973, 428 pp.
  41. ^ "You Never Get a Seventh Chance to Make a First Impression: An Awkward History of Our Space Transmissions". Lightspeed Magazine. March 2011. Retrieved 13 March 2015.
  42. ^ "Stephen Hawking: Humans Should Fear Aliens". Huffington Post. 25 June 2010. Retrieved 27 May 2017.
  43. ^ Zahnle, K.; Schaefer, L.; Fegley, B. (October 2010). "Earth's Earliest Atmospheres". Cold Spring Harbor Perspectives in Biology. 2 (10): a004895. doi:10.1101/cshperspect.a004895. PMC 2944365. PMID 20573713.
  44. ^ Tarduno, John A.; Cottrell, Rory D.; Bono, Richard K.; Oda, Hirokuni; Davis, William J.; Fayek, Mostafa; Erve, Olaf van 't; Nimmo, Francis; Huang, Wentao; Thern, Eric R.; Fearn, Sebastian; Mitra, Gautam; Smirnov, Aleksey V.; Blackman, Eric G. (21 January 2020). "Paleomagnetism indicates that primary magnetite in zircon records a strong Hadean geodynamo". Proceedings of the National Academy of Sciences. 117 (5): 2309–2318. Bibcode:2020PNAS..117.2309T. doi:10.1073/pnas.1916553117. PMC 7007582. PMID 31964848.
  45. ^ Müller, Ulrich F.; Elsila, Jamie; Trail, Dustin; Dasgupta, Saurja; Giese, Claudia-Corina; Walton, Craig R.; Cohen, Zachary R.; Stolar, Tomislav; Krishnamurthy, Ramanarayanan; Lyons, Timothy W.; Rogers, Karyn L.; Williams, Loren Dean (7 July 2022). "Frontiers in Prebiotic Chemistry and Early Earth Environments". Origins of Life and Evolution of Biospheres. 52 (1–3): 165–181. Bibcode:2022OLEB...52..165M. doi:10.1007/s11084-022-09622-x. PMC 9261198. PMID 35796897.
  46. ^ Osinski, G.R.; Cockell, C.S.; Pontefract, A.; Sapers, H.M. (15 September 2020). "The Role of Meteorite Impacts in the Origin of Life". Astrobiology. 20 (9): 1121–1149. Bibcode:2020AsBio..20.1121O. doi:10.1089/ast.2019.2203. PMC 7499892. PMID 32876492.
  47. ^ Rodriguez, Laura E.; House, Christopher H.; Smith, Karen E.; Roberts, Melissa R.; Callahan, Michael P. (26 June 2019). "Nitrogen heterocycles form peptide nucleic acid precursors in complex prebiotic mixtures". Scientific Reports. 9 (1): 9281. Bibcode:2019NatSR...9.9281R. doi:10.1038/s41598-019-45310-z. PMC 6594999. PMID 31243303.
  48. ^ Kloprogge, Jacob; Hartman, Hyman (9 February 2022). "Clays and the Origin of Life: The Experiments". Life. 12 (2): 259. Bibcode:2022Life...12..259K. doi:10.3390/life12020259. PMC 8880559. PMID 35207546.
  49. ^ Hess, Benjamin; Piazolo, Sandra; Harvey, Jason (16 March 2021). "Lightning strikes as a major facilitator of prebiotic phosphorus reduction on early Earth". Nature Communications. 12 (1): 1535. Bibcode:2021NatCo..12.1535H. doi:10.1038/s41467-021-21849-2. PMC 7966383. PMID 33727565.
  50. ^ Kempe, Stephan; Kazmierczak, Jozef (Spring 2002). "Biogenesis and early life on Earth and Europa: favored by an alkaline ocean?". Astrobiology. 2 (1): 123–130. Bibcode:2002AsBio...2..123K. doi:10.1089/153110702753621394. PMID 12449860.
  51. ^ "Sources of Organics on Earth". Astrobiology at NASA. NASA. Retrieved 29 January 2023.
  52. ^ Satkoski, Aaron M.; Fralick, Philip; Beard, Brian L.; Johnson, Clark M. (15 July 2017). "Initiation of modern-style plate tectonics recorded in Mesoarchean marine chemical sediments". Geochimica et Cosmochimica Acta. 209: 216–232. Bibcode:2017GeCoA.209..216S. doi:10.1016/j.gca.2017.04.024.
  53. ^ Lindsay, John; McKay, David; Allen, Carlton (Winter 2003). "Earth's Earliest Biosphere—A Proposal to Develop a Collection of Curated Archean Geologic Reference Materials". Astrobiology. 3 (4): 739–758. Bibcode:2003AsBio...3..739L. doi:10.1089/153110703322736060. PMID 14987479.
  54. ^ McMahon, Sean (4 December 2019). "Earth's earliest and deepest purported fossils may be iron-mineralized chemical gardens". Proceedings: Biological Sciences. 286 (1916): 1916. doi:10.1098/rspb.2019.2410. PMC 6939263. PMID 31771469. S2CID 208296652.
  55. ^ "NASA Astrobiology: Life in the Universe". Archived from the original on 23 March 2008. Retrieved 13 March 2015.
  56. ^ Griffin, Dale Warren (14 August 2013). "The Quest for Extraterrestrial Life: What About the Viruses?". Astrobiology. 13 (8): 774–783. Bibcode:2013AsBio..13..774G. doi:10.1089/ast.2012.0959. PMID 23944293.
  57. ^ Berliner, Aaron J.; Mochizuki, Tomohiro; Stedman, Kenneth M. (2018). "Astrovirology: Viruses at Large in the Universe". Astrobiology. 18 (2): 207–223. Bibcode:2018AsBio..18..207B. doi:10.1089/ast.2017.1649. PMID 29319335. S2CID 4348200.
  58. ^ Janjic, Aleksandar (2018). "The Need for Including Virus Detection Methods in Future Mars Missions". Astrobiology. 18 (12): 1611–1614. Bibcode:2018AsBio..18.1611J. doi:10.1089/ast.2018.1851. S2CID 105299840.
  59. ^ No, NASA Hasn't Found Alien Life. Mike Wall, Space. 26 June 2017.
  60. ^ Crenson, Matt (6 August 2006). "Experts: Little Evidence of Life on Mars". Associated Press. Archived from the original on 16 April 2011. Retrieved 8 March 2011.
  61. ^ McKay DS; Gibson E. K.; Thomas-Keprta K. L.; Vali H.; Romanek C. S.; Clemett S. J.; Chillier X. D. F.; Maechling C. R.; Zare R. N. (1996). "Search for past life on Mars: Possible relic biogenic activity in Martian meteorite ALH84001". Science. 273 (5277): 924–930. Bibcode:1996Sci...273..924M. doi:10.1126/science.273.5277.924. PMID 8688069. S2CID 40690489.
  62. ^ McKay David S.; Thomas-Keprta K. L.; Clemett, S. J.; Gibson, E. K. Jr; Spencer L.; Wentworth S. J. (2009). Hoover, Richard B.; Levin, Gilbert V.; Rozanov, Alexei Y.; Retherford, Kurt D. (eds.). "Life on Mars: new evidence from martian meteorites". Proc. SPIE. Proceedings of SPIE. 7441 (1): 744102. Bibcode:2009SPIE.7441E..02M. doi:10.1117/12.832317. S2CID 123296237. Retrieved 8 March 2011.
  63. ^ Webster, Guy (27 February 2014). "NASA Scientists Find Evidence of Water in Meteorite, Reviving Debate Over Life on Mars". NASA. Archived from the original on 1 March 2014. Retrieved 27 February 2014.
  64. ^ White, Lauren M.; Gibson, Everett K.; Thomnas-Keprta, Kathie L.; Clemett, Simon J.; McKay, David (19 February 2014). "Putative Indigenous Carbon-Bearing Alteration Features in Martian Meteorite Yamato 000593". Astrobiology. 14 (2): 170–181. Bibcode:2014AsBio..14..170W. doi:10.1089/ast.2011.0733. PMC 3929347. PMID 24552234.
  65. ^ Gannon, Megan (28 February 2014). "Mars Meteorite with Odd 'Tunnels' & 'Spheres' Revives Debate Over Ancient Martian Life". Space.com. Retrieved 28 February 2014.
  66. ^ Tenney, Garrett (5 March 2011). "Exclusive: NASA Scientist Claims Evidence of Alien Life on Meteorite". Fox News. Archived from the original on 6 March 2011. Retrieved 6 March 2011.
  67. ^ Hoover, Richard B. (2011). "Fossils of Cyanobacteria in CI1 Carbonaceous Meteorites: Implications to Life on Comets, Europa, and Enceladus". Journal of Cosmology. 13: xxx. Archived from the original on 8 March 2011. Retrieved 6 March 2011.
  68. ^ Sheridan, Kerry (7 March 2011). "NASA shoots down alien fossil claims". ABC News. Retrieved 7 March 2011.
  69. ^ Tyson, Neil deGrasse (23 July 2001). "The Search for Life in the Universe". Department of Astrophysics and Hayden Planetarium. NASA. Archived from the original on 21 July 2011. Retrieved 7 March 2011.
  70. ^ "Kepler Mission". NASA. 2008. Archived from the original on 31 October 2008. Retrieved 20 October 2008.
  71. ^ "The COROT space telescope". CNES. 17 October 2008. Archived from the original on 8 November 2008. Retrieved 20 October 2008.
  72. ^ Gertner, Jon (15 September 2022). "The Search for Intelligent Life Is About to Get a Lot More Interesting - There are an estimated 100 billion galaxies in the universe, home to an unimaginable abundance of planets. And now there are new ways to spot signs of life on them". The New York Times. Retrieved 15 September 2022.
  73. ^ "The Virtual Planet Laboratory". NASA. 2008. Retrieved 20 October 2008.
  74. ^ Ford, Steve (August 1995). "What is the Drake Equation?". SETI League. Archived from the original on 29 October 2008. Retrieved 20 October 2008.
  75. ^ Amir Alexander. "The Search for Extraterrestrial Intelligence: A Short History – Part 7: The Birth of the Drake Equation".
  76. ^ a b "Astrobiology". Biology Cabinet. 26 September 2006. Archived from the original on 12 December 2010. Retrieved 17 January 2011.
  77. ^ Horner, Jonathan; Barrie Jones (24 August 2007). "Jupiter: Friend or foe?". Europlanet. Archived from the original on 2 February 2012. Retrieved 20 October 2008.
  78. ^ Jakosky, Bruce; David Des Marais; et al. (14 September 2001). "The Role of Astrobiology in Solar System Exploration". NASA. SpaceRef.com. Retrieved 20 October 2008.[permanent dead link]
  79. ^ Bortman, Henry (29 September 2004). "Coming Soon: "Good" Jupiters". Astrobiology Magazine. Archived from the original on 8 February 2012. Retrieved 20 October 2008.{{cite web}}: CS1 maint: unfit URL (link)
  80. ^ "Living at the Extremes: Extremophiles and the Limits of Life in a Planetary Context." N. Merino, H.S. Aronson, D. Bojanova, J. Feyhl-Buska, et al. EarthArXiv. February 2019.
  81. ^ a b Chamberlin, Sean (1999). "Black Smokers and Giant Worms". Fullerton College. Retrieved 11 February 2011.
  82. ^ a b Trixler, F (2013). "Quantum tunnelling to the origin and evolution of life". Current Organic Chemistry. 17 (16): 1758–1770. doi:10.2174/13852728113179990083. PMC 3768233. PMID 24039543.
  83. ^ Carey, Bjorn (7 February 2005). "Wild Things: The Most Extreme Creatures". Live Science. Retrieved 20 October 2008.
  84. ^ a b Cavicchioli, R. (Fall 2002). "Extremophiles and the search for extraterrestrial life" (PDF). Astrobiology. 2 (3): 281–292. Bibcode:2002AsBio...2..281C. CiteSeerX 10.1.1.472.3179. doi:10.1089/153110702762027862. PMID 12530238. Archived (PDF) from the original on 9 October 2022.
  85. ^ Young, Kelly (10 November 2005). "Hardy lichen shown to survive in space". New Scientist. Retrieved 17 January 2019.
  86. ^ a b c d e f The Planetary Report, Volume XXIX, number 2, March/April 2009, "We make it happen! Who will survive? Ten hardy organisms selected for the LIFE project, by Amir Alexander
  87. ^ Hashimoto, T.; Kunieda, T. (2017). "DNA Protection protein, a novel mechanism of radiation tolerance: Lessons from Tardigrades". Life. 7 (2): 26. Bibcode:2017Life....7...26H. doi:10.3390/life7020026. PMC 5492148. PMID 28617314.
  88. ^ "Jupiter's Moon Europa Suspected of Fostering Life". Daily University Science News. 2002. Retrieved 8 August 2009.
  89. ^ Cavicchioli, R. (Fall 2002). "Extremophiles and the search for extraterrestrial life". Astrobiology. 2 (3): 281–292. Bibcode:2002AsBio...2..281C. CiteSeerX 10.1.1.472.3179. doi:10.1089/153110702762027862. PMID 12530238.
  90. ^ David, Leonard (7 February 2006). "Europa Mission: Lost in NASA Budget". Space.com. Retrieved 8 August 2009.
  91. ^ "Clues to possible life on Europa may lie buried in Antarctic ice". Marshal Space Flight Center. NASA. 5 March 1998. Archived from the original on 31 July 2009. Retrieved 8 August 2009.
  92. ^ Lovett, Richard A. (31 May 2011). "Enceladus named sweetest spot for alien life". Nature. doi:10.1038/news.2011.337. Retrieved 3 June 2011.
  93. ^ a b Chow, Denise (26 October 2011). "Discovery: Cosmic Dust Contains Organic Matter from Stars". Space.com. Retrieved 26 October 2011.
  94. ^ ScienceDaily Staff (26 October 2011). "Astronomers Discover Complex Organic Matter Exists Throughout the Universe". ScienceDaily. Retrieved 27 October 2011.
  95. ^ Kwok, Sun; Zhang, Yong (26 October 2011). "Mixed aromatic–aliphatic organic nanoparticles as carriers of unidentified infrared emission features". Nature. 479 (7371): 80–83. Bibcode:2011Natur.479...80K. doi:10.1038/nature10542. PMID 22031328. S2CID 4419859.
  96. ^ Hoover, Rachel (21 February 2014). "Need to Track Organic Nano-Particles Across the Universe? NASA's Got an App for That". NASA. Archived from the original on 6 September 2015. Retrieved 22 February 2014.
  97. ^ Staff (20 September 2012). "NASA Cooks Up Icy Organics to Mimic Life's Origins". Space.com. Retrieved 22 September 2012.
  98. ^ Gudipati, Murthy S.; Yang, Rui (1 September 2012). "In-Situ Probing of Radiation-Induced Processing of Organics in Astrophysical Ice Analogs – Novel Laser Desorption Laser Ionization Time-Of-Flight Mass Spectroscopic Studies". The Astrophysical Journal Letters. 756 (1): L24. Bibcode:2012ApJ...756L..24G. doi:10.1088/2041-8205/756/1/L24. S2CID 5541727.
  99. ^ Gough, Evan (6 October 2020). "Here's a Clever Idea, Looking for the Shadows of Trees On Exoplanets to Detect Multicellular Life". Universe Today. Retrieved 7 October 2020.
  100. ^ Doughty, Christopher E.; et al. (1 October 2020). "Distinguishing multicellular life on exoplanets by testing Earth as an exoplanet". International Journal of Astrobiology. 19 (6): 492–499. arXiv:2002.10368. Bibcode:2020IJAsB..19..492D. doi:10.1017/S1473550420000270.
  101. ^ Grinspoon, David (2004). Lonely Planets: The Natural Philosophy of Alien Life. New York: ECCO. ISBN 978-0-06-018540-4.
  102. ^ Dunér, David (2013). "Introduction". In Dunér, David (ed.). The History and Philosophy of Astrobiology: Perspectives on Extraterrestrial Life and the Human Mind. Newcastle upon Tyne: Cambridge Scholars Publishing. p. 4.
  103. ^ Persson, Erik (2013). "Philosophical Aspects of Astrobiology". In Dunér, David (ed.). The History and Philosophy of Astrobiology: Perspectives on Extraterrestrial Life and the Human Mind. Newcastle upon Tyne: Cambridge Scholars Publishing.
  104. ^ Von Egner, Ian (2019). "Astrobiology and astrophilosophy: Subsuming or bifurcating disciplines". Philosophy and Cosmology. 23: 62–79.
  105. ^ Kristina Šekrst. "Astrobiology in Philosophy or Philosophy in Astrobiology". Cosmos and History.
  106. ^ Kolb, Vera (2015). "Philosophy of Astrobiology: Some Recent Developments". In Hoover, Richard B. (ed.). Proc. SPIE 9606, Instruments, Methods, and Missions for Astrobiology XVII. pp. 960605-1–960605-6.
  107. ^ Schneider, Sean (2013). "Philosophical Problems of the Definition of Extraterrestrial Life and Intelligence". In Dunér, David (ed.). The History and Philosophy of Astrobiology: Perspectives on Extraterrestrial Life and the Human Mind. Newcastle upon Tyne: Cambridge Scholars Publishing. p. 132.
  108. ^ Chambers, Paul (1999). Life on Mars; The Complete Story. London: Blandford. ISBN 978-0-7137-2747-0.
  109. ^ Levin, G and P. Straaf. 1976. "Viking Labeled Release Biology Experiment: Interim Results". Science: 194. 1322–1329.
  110. ^ Bianciardi, Giorgio; Miller, Joseph D.; Straat, Patricia Ann; Levin, Gilbert V. (March 2012). "Complexity Analysis of the Viking Labeled Release Experiments". IJASS. 13 (1): 14–26. Bibcode:2012IJASS..13...14B. doi:10.5139/IJASS.2012.13.1.14.
  111. ^ Klotz, Irene (12 April 2012). "Mars Viking Robots 'Found Life'". Discovery News. Archived from the original on 14 April 2012. Retrieved 16 April 2012.
  112. ^ Navarro-González, R.; et al. (2006). "The limitations on organic detection in Mars-like soils by thermal volatilization–gas chromatography – MS and their implications for the Viking results". PNAS. 103 (44): 16089–16094. Bibcode:2006PNAS..10316089N. doi:10.1073/pnas.0604210103. PMC 1621051. PMID 17060639.
  113. ^ Paepe, Ronald (2007). "The Red Soil on Mars as a proof for water and vegetation" (PDF). Geophysical Research Abstracts. 9 (1794). Archived from the original (PDP) on 13 June 2011. Retrieved 2 May 2012.
  114. ^ Horowitz, N.H. (1986). Utopia and Back and the search for life in the solar system. New York: W.H. Freeman and Company. ISBN 0-7167-1766-2
  115. ^ "Beagle 2 : the British led exploration of Mars". Archived from the original on 4 March 2016. Retrieved 13 March 2015.
  116. ^ Elke Rabbow; Gerda Horneck; Petra Rettberg; Jobst-Ulrich Schott; Corinna Panitz; Andrea L'Afflitto; Ralf von Heise-Rotenburg; Reiner Willnecker; Pietro Baglioni; Jason Hatton; Jan Dettmann; René Demets; Günther Reitz (9 July 2009). "Expose, an Astrobiological Exposure Facility on the International Space Station – from Proposal to Flight" (PDF). Orig Life Evol Biosph. 39 (6): 581–598. Bibcode:2009OLEB...39..581R. doi:10.1007/s11084-009-9173-6. PMID 19629743. S2CID 19749414. Archived from the original (PDF) on 10 January 2014. Retrieved 8 July 2013.
  117. ^ Karen Olsson-Francis; Charles S. Cockell (23 October 2009). "Experimental methods for studying microbial survival in extraterrestrial environments" (PDF). Journal of Microbiological Methods. 80 (1): 1–13. doi:10.1016/j.mimet.2009.10.004. PMID 19854226. Archived from the original (PDF) on 18 September 2013. Retrieved 31 July 2013.
  118. ^ "Expose – home page". Centre national d'études spatiales (CNES). Archived from the original on 15 January 2013. Retrieved 8 July 2013.
  119. ^ "Name NASA's Next Mars Rover". NASA/JPL. 27 May 2009. Archived from the original on 22 May 2009. Retrieved 27 May 2009.
  120. ^ "Mars Science Laboratory: Mission". NASA/JPL. Archived from the original on 5 March 2006. Retrieved 12 March 2010.
  121. ^ a b "Early Tanpopo mission results show microbes can survive in space". American Geophysical Union. Geospace. Larry O'Hanlon. 19 May 2017.
  122. ^ Amos, Jonathan (15 March 2012). "Europe still keen on Mars missions". BBC News. Retrieved 16 March 2012.
  123. ^ Svitak, Amy (16 March 2012). "Europe Joins Russia on Robotic ExoMars". Aviation Week. Retrieved 16 March 2012.[permanent dead link]
  124. ^ Selding, Peter B. de (15 March 2012). "ESA Ruling Council OKs ExoMars Funding". Space News. Archived from the original on 6 December 2012. Retrieved 16 March 2012.
  125. ^ Foust, Jeff (10 April 2024). "ESA awards contract to Thales Alenia Space to restart ExoMars". SpaceNews. Retrieved 11 April 2024.
  126. ^ Cowing, Keith (21 December 2012). "Science Definition Team for the 2020 Mars Rover". NASA. Science Ref. Retrieved 21 December 2012.[permanent dead link]
  127. ^ "Science Team Outlines Goals for NASA's 2020 Mars Rover". Jet Propulsion Laboratory. NASA. 9 July 2013. Retrieved 10 July 2013.
  128. ^ "Mars 2020 Science Definition Team Report – Frequently Asked Questions" (PDF). NASA. 9 July 2013. Retrieved 10 July 2013.
  129. ^ "NASA's Europa Clipper launches aboard SpaceX rocket, bound for Jupiter's icy ocean moon". Los Angeles Times. 14 October 2024. Retrieved 14 October 2024.
  130. ^ "Europa Clipper". Jet Propulsion Laboratory. NASA. November 2013. Archived from the original on 13 December 2013. Retrieved 13 December 2013.
  131. ^ Kane, Van (26 May 2013). "Europa Clipper Update". Future Planetary Exploration. Retrieved 13 December 2013.
  132. ^ Pappalardo, Robert T.; S. Vance; F. Bagenal; B.G. Bills; D.L. Blaney; D.D. Blankenship; W.B. Brinckerhoff; et al. (2013). "Science Potential from a Europa Lander" (PDF). Astrobiology. 13 (8): 740–773. Bibcode:2013AsBio..13..740P. doi:10.1089/ast.2013.1003. hdl:1721.1/81431. PMID 23924246. S2CID 10522270. Archived (PDF) from the original on 9 October 2022.
  133. ^ Senske, D. (2 October 2012), "Europa Mission Concept Study Update", Presentation to Planetary Science Subcommittee (PDF), retrieved 14 December 2013
  134. ^ Dragonfly: A Rotorcraft Lander Concept for Scientific Exploration at Titan Ralph D. Lorenz, Elizabeth P. Turtle, Jason W. Barnes, Melissa G. Trainer, Douglas S. Adams, Kenneth E. Hibbard, Colin Z. Sheldon, Kris Zacny, Patrick N. Peplowski, David J. Lawrence, Michael A. Ravine, Timothy G. McGee, Kristin S. Sotzen, Shannon M. MacKenzie, Jack W. Langelaan, Sven Schmitz, Larry S. Wolfarth, and Peter D. Bedini. 2018. Johns Hopkins APL Technical Digest, 34(3), 374-387
  135. ^ Christopher P. McKay; Carol R. Stoker; Brian J. Glass; Arwen I. Davé; Alfonso F. Davila; Jennifer L. Heldmann; et al. (5 April 2013). "The Icebreaker Life Mission to Mars: A Search for Biomolecular Evidence for Life". Astrobiology. 13 (4): 334–353. Bibcode:2013AsBio..13..334M. doi:10.1089/ast.2012.0878. PMID 23560417.
  136. ^ Choi, Charles Q. (16 May 2013). "Icebreaker Life Mission". Astrobiology Magazine. Archived from the original on 9 October 2015. Retrieved 1 July 2013.{{cite news}}: CS1 maint: unfit URL (link)
  137. ^ C. P. McKay; Carol R. Stoker; Brian J. Glass; Arwen I. Davé; Alfonso F. Davila; Jennifer L. Heldmann; et al. (2012). "The Icebreaker Life Mission to Mars: A Search for Biochemical Evidence for Life". Concepts and Approaches for Mars Exploration (PDF). Lunar and Planetary Institute. Retrieved 1 July 2013.
  138. ^ Sotin, C.; Altwegg, K.; Brown, R.H.; et al. (2011). JET: Journey to Enceladus and Titan (PDF). 42nd Lunar and Planetary Science Conference. Lunar and Planetary Institute. Archived (PDF) from the original on 9 October 2022.
  139. ^ Kane, Van (3 April 2014). "Discovery Missions for an Icy Moon with Active Plumes". The Planetary Society. Retrieved 9 April 2015.
  140. ^ Matousek, Steve; Sotin, Christophe; Goebel, Dan; Lang, Jared (18–21 June 2013). JET: Journey to Enceladus and Titan (PDF). Low Cost Planetary Missions Conference. California Institute of Technology. Archived from the original (PDF) on 4 March 2016. Retrieved 10 April 2015.
  141. ^ Lunine, Jonathan I.; Waite, Jack Hunter Jr.; Postberg, Frank; Spilker, Linda J. (2015). Enceladus Life Finder: The search for life in a habitable moon (PDF). 46th Lunar and Planetary Science Conference. Houston (TX): Lunar and Planetary Institute. Archived (PDF) from the original on 9 October 2022.
  142. ^ Clark, Stephen (6 April 2015). "Diverse destinations considered for new interplanetary probe". Space Flight Now. Retrieved 7 April 2015.
  143. ^ Tsou, Peter; Brownlee, D.E.; McKay, Christopher; Anbar, A.D.; Yano, H. (August 2012). "Life Investigation For Enceladus A Sample Return Mission Concept in Search for Evidence of Life". Astrobiology. 12 (8): 730–742. Bibcode:2012AsBio..12..730T. doi:10.1089/ast.2011.0813. PMID 22970863.
  144. ^ Tsou, Peter; Anbar, Ariel; Atwegg, Kathrin; Porco, Carolyn; Baross, John; McKay, Christopher (2014). "Life – Enceladus Plume Sample Return via Discovery" (PDF). 45th Lunar and Planetary Science Conference (1777): 2192. Bibcode:2014LPI....45.2192T. Archived (PDF) from the original on 9 October 2022. Retrieved 10 April 2015.
  145. ^ Tsou, Peter (2013). "Life Investigation For Enceladus – A Sample Return Mission Concept in Search for Evidence of Life". Jet Propulsion Laboratory. 12 (8): 730–742. Bibcode:2012AsBio..12..730T. doi:10.1089/ast.2011.0813. PMID 22970863. Archived from the original (.doc) on 1 September 2015. Retrieved 10 April 2015.
  146. ^ Sotin, C.; Hayes, A.; Malaska, M.; Nimmo, F.; Trainer, M.; Mastrogiuseppe, M.; et al. (20–24 March 2017). Oceanus: A New Frontiers orbiter to study Titan's potential habitability (PDF). 48th Lunar and Planetary Science Conference. The Woodlands, Texas.
  147. ^ Tortora, P.; Zannoni, M.; Nimmo, F.; Mazarico, E.; Iess, L.; Sotin, C.; Hayes, A.; Malaska, M. (23–28 April 2017). Titan gravity investigation with the Oceanus mission. 19th EGU General Assembly, EGU2017. EGU General Assembly Conference Abstracts. Vol. 19. p. 17876. Bibcode:2017EGUGA..1917876T.
  148. ^ Mitri, Giuseppe; Postberg, Frank; Soderblom, Jason M.; Tobie, Gabriel; Tortora, Paolo; Wurz, Peter; et al. (2017). "Explorer of Enceladus and Titan (E2T): Investigating the habitability and evolution of ocean worlds in the Saturn system". American Astronomical Society. 48: 225.01. Bibcode:2016DPS....4822501M. Retrieved 16 September 2017.

General references

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Further reading

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