Life on other planets

Life on other planets

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first of all I'm not sure if I should post this here or in the astronomy stack. I think biologist are more likely to answer my question. To make it short:

Why when looking for any sort of life on other planets, we keep looking for similar conditions we call "life friendly", like nice temperature, oxygen level, pressure etc…

Is there some rule in biology that says life can only exists under these conditions? Why nobody supposes that evolution did not have enough time yet on our planet to generate other living mechanisms, and that on other planets even if the conditions are not suitable for us, there might be something well evolved through time there. After all if we can conceive electric robots that can survive to radioactivity and to high pressures and temperatures, why nature shouldn't be able to?

We might imagine living things that are very different from what we know. There is no conceptual reason for limiting life in its relation to water for example. Moreover, the definition of what is alive is really unclear. We classified more or less arbitrarily objects we know on earth as being living or not living but this does not give any clear definition of what is life and therefore it would not allow an exobiologist to even know what he's looking for!

But if you had to seek in billion of planets/natural satellite a living creature somewhere where what planets would start looking at? Probably those that look alike yours because you already know that life is possible the kind of conditions these planets offer. I think the answer is as easy as that.


The term was first proposed by the Russian (Soviet) astronomer Gavriil Tikhov in 1953. [28] Astrobiology is etymologically derived from the Greek ἄστρον , astron, "constellation, star" βίος , bios, "life" and -λογία , -logia, study. The synonyms of astrobiology are diverse however, the synonyms were structured in relation to the most important sciences implied in its development: astronomy and biology. A close synonym is exobiology from the Greek Έξω , "external" Βίος, bios, "life" and λογία, -logia, study. The term exobiology was coined by molecular biologist and Nobel Prize winner Joshua Lederberg. [29] Exobiology is considered to have a narrow scope limited to search of life external to Earth, whereas subject area of astrobiology is wider and investigates the link between life and the universe, which includes the search for extraterrestrial life, but also includes the study of life on Earth, its origin, evolution and limits.

Another term used in the past is xenobiology, ("biology of the foreigners") a word used in 1954 by science fiction writer Robert Heinlein in his work The Star Beast. [31] The term xenobiology is now used in a more specialized sense, to mean "biology based on foreign chemistry", whether of extraterrestrial or terrestrial (possibly synthetic) origin. Since alternate chemistry analogs to some life-processes have been created in the laboratory, xenobiology is now considered as an extant subject. [32]

While it is an emerging and developing field, the question of whether life exists elsewhere in the universe is a verifiable hypothesis and thus a valid line of scientific inquiry. [33] [34] Though once considered outside the mainstream of scientific inquiry, astrobiology has become a formalized field of study. Planetary scientist David Grinspoon calls astrobiology a field of natural philosophy, grounding speculation on the unknown, in known scientific theory. [35] NASA's interest in exobiology first began with the development of the U.S. Space Program. In 1959, NASA funded its first exobiology project, and in 1960, NASA founded an Exobiology Program, which is now one of four main elements of NASA's current Astrobiology Program. [2] [36] In 1971, NASA funded the search for extraterrestrial intelligence (SETI) to search radio frequencies of the electromagnetic spectrum for interstellar communications transmitted by extraterrestrial life outside the Solar System. NASA's Viking missions to Mars, launched in 1976, included three biology experiments designed to look for metabolism of present life on Mars.

Advancements in the fields of astrobiology, observational astronomy and discovery of large varieties of extremophiles with extraordinary capability to thrive in the harshest environments on Earth, have led to speculation that life may possibly be thriving on many of the extraterrestrial bodies in the universe. [12] A particular focus of current astrobiology research is the search for life on Mars due to this planet's proximity to Earth and geological history. There is a growing body of evidence to suggest that Mars has previously had a considerable amount of water on its surface, [37] [38] water being considered an essential precursor to the development of carbon-based life. [39]

Missions specifically designed to search for current life on Mars were the Viking program and Beagle 2 probes. The Viking results were inconclusive, [40] and Beagle 2 failed minutes after landing. [41] A future mission with a strong astrobiology role would have been the Jupiter Icy Moons Orbiter, designed to study the frozen moons of Jupiter—some of which may have liquid water—had it not been cancelled. In late 2008, the Phoenix lander probed the environment for past and present planetary habitability of microbial life on Mars, and researched the history of water there.

The European Space Agency's astrobiology roadmap from 2016, identified five main research topics, and specifies several key scientific objectives for each topic. The five research topics are: [42] 1) Origin and evolution of planetary systems 2) Origins of organic compounds in space 3) Rock-water-carbon interactions, organic synthesis on Earth, and steps to life 4) Life and habitability 5) Biosignatures as facilitating life detection.

In November 2011, NASA launched the Mars Science Laboratory mission carrying the Curiosity rover, which landed on Mars at Gale Crater in August 2012. [43] [44] [45] The Curiosity rover is currently probing the environment for past and present planetary habitability of microbial life on Mars. On 9 December 2013, NASA reported that, based on evidence from Curiosity studying Aeolis Palus, Gale Crater contained an ancient freshwater lake which could have been a hospitable environment for microbial life. [46] [25]

The European Space Agency is currently collaborating with the Russian Federal Space Agency (Roscosmos) and developing the ExoMars astrobiology rover, which was scheduled to be launched in July 2020, but was postponed to 2022. [47] Meanwhile, NASA launched the Mars 2020 astrobiology rover and sample cacher for a later return to Earth.

Planetary habitability Edit

When looking for life on other planets like Earth, some simplifying assumptions are useful to reduce the size of the task of the astrobiologist. One is the informed assumption that the vast majority of life forms in our galaxy are based on carbon chemistries, as are all life forms on Earth. [48] Carbon is well known for the unusually wide variety of molecules that can be formed around it. 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.

The presence of liquid water is an assumed requirement, as it is a common molecule and provides an excellent environment for the formation of complicated carbon-based molecules that could eventually lead to the emergence of life. [49] [50] Some researchers posit environments of water-ammonia mixtures as possible solvents for hypothetical types of biochemistry. [51]

A third assumption is to focus on planets orbiting Sun-like stars for increased probabilities of planetary habitability. [52] 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. [53] The long lifetimes of red dwarfs could allow the development of habitable environments on planets with thick atmospheres. This is significant, as red dwarfs are extremely common. (See Habitability of red dwarf systems).

Since Earth is the only planet known to harbor life, there is no evident way to know if any of these simplifying assumptions are correct.

Communication attempts Edit

Research on communication with extraterrestrial intelligence (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. The SETI program, for example, uses both radio telescopes and optical telescopes to search for deliberate signals from an extraterrestrial intelligence.

While some high-profile scientists, such as Carl Sagan, have advocated the transmission of messages, [54] [55] scientist Stephen Hawking warned against it, suggesting that aliens might simply raid Earth for its resources and then move on. [56]

Elements of astrobiology Edit

Astronomy Edit

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. [57] [58] 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. 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, [59] 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: [60]

N = R ∗ × f p × n e × f l × f i × f c × L

  • N = The number of communicative civilizations
  • R* = The rate of formation of suitable stars (stars such as our 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, [61] but some applications of the formula had been taken literally and related to simplistic or pseudoscientific arguments. [62] 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) [63] may have greatly increased the probability of intelligent life arising on our planet. [64] [65]

Biology Edit

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. [62] 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. [66]

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. [67] 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. [67] These creatures thrive despite having no access to sunlight, and it was soon discovered that they comprise 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. [68] This chemosynthesis revolutionized the study of biology and astrobiology by revealing that life need not be sun-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. [69] [70] 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 Xanthoria elegans, [71] the bacterium Bacillus safensis, [72] Deinococcus radiodurans, [72] Bacillus subtilis, [72] yeast Saccharomyces cerevisiae, [72] seeds from Arabidopsis thaliana ('mouse-ear cress'), [72] as well as the invertebrate animal Tardigrade. [72] 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. [73]

Jupiter's moon, Europa, [70] [74] [75] [76] [77] [78] and Saturn's moon, Enceladus, [79] [80] 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. [68]

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 panspermia hypothesis.

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. [81] [82] [83] 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." [81]

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. [84] 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". [85] [86]

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. [87] [88]

Astroecology Edit

Astroecology concerns the interactions of life with space environments and resources, in planets, asteroids and comets. On a larger scale, astroecology concerns resources for life about stars in the galaxy through the cosmological future. Astroecology attempts to quantify future life in space, addressing this area of astrobiology.

Experimental astroecology investigates resources in planetary soils, using actual space materials in meteorites. [89] The results suggest that Martian and carbonaceous chondrite materials can support bacteria, algae and plant (asparagus, potato) cultures, with high soil fertilities. The results support that life could have survived in early aqueous asteroids and on similar materials imported to Earth by dust, comets and meteorites, and that such asteroid materials can be used as soil for future space colonies. [89] [90]

On the largest scale, cosmoecology concerns life in the universe over cosmological times. The main sources of energy may be red giant stars and white and red dwarf stars, sustaining life for 10 20 years. [89] [91] Astroecologists suggest that their mathematical models may quantify the potential amounts of future life in space, allowing a comparable expansion in biodiversity, potentially leading to diverse intelligent life forms. [92]

Astrogeology Edit

Astrogeology is a planetary science discipline concerned with the geology of celestial bodies such as the planets and their moons, asteroids, comets, and meteorites. The information gathered by this discipline allows the measure of a planet's or a natural satellite's potential to develop and sustain life, or planetary habitability.

An additional discipline of astrogeology is geochemistry, which involves study of the chemical composition of the Earth and other planets, chemical processes and reactions that govern the composition of rocks and soils, the cycles of matter and energy and their interaction with the hydrosphere and the atmosphere of the planet. Specializations include cosmochemistry, biochemistry and organic geochemistry.

The fossil record provides the oldest known evidence for life on Earth. [93] By examining the fossil evidence, paleontologists are able to better understand the types of organisms that arose on the early Earth. Some regions on Earth, such as the Pilbara in Western Australia and the McMurdo Dry Valleys of Antarctica, are also considered to be geological analogs to regions of Mars, and as such, might be able to provide clues on how to search for past life on Mars.

The various organic functional groups, composed of hydrogen, oxygen, nitrogen, phosphorus, sulfur, and a host of metals, such as iron, magnesium, and zinc, provide the enormous diversity of chemical reactions necessarily catalyzed by a living organism. Silicon, in contrast, interacts with only a few other atoms, and the large silicon molecules are monotonous compared with the combinatorial universe of organic macromolecules. [62] [94] Indeed, it seems likely that the basic building blocks of life anywhere will be similar to those on Earth, in the generality if not in the detail. [94] Although terrestrial life and life that might arise independently of Earth are expected to use many similar, if not identical, building blocks, they also are expected to have some biochemical qualities that are unique. If life has had a comparable impact elsewhere in the Solar System, the relative abundances of chemicals key for its survival—whatever they may be—could betray its presence. Whatever extraterrestrial life may be, its tendency to chemically alter its environment might just give it away. [95]

People have long speculated about the possibility of life in settings other than Earth, however, speculation on the nature of life elsewhere often has paid little heed to constraints imposed by the nature of biochemistry. [94] The likelihood that life throughout the universe is probably carbon-based is suggested by the fact that carbon is one of the most abundant of the higher elements. Only two of the natural atoms, carbon and silicon, are known to serve as the backbones of molecules sufficiently large to carry biological information. As the structural basis for life, one of carbon's important features is that, unlike silicon, it can readily engage in the formation of chemical bonds with many other atoms, thereby allowing for the chemical versatility required to conduct the reactions of biological metabolism and propagation.

Discussion on where in the Solar System life might occur was limited historically by the understanding that life relies ultimately on light and warmth from the Sun and, therefore, is restricted to the surfaces of planets. [94] The four most likely candidates for life in the Solar System are the planet Mars, the Jovian moon Europa, and Saturn's moons Titan [96] [97] [98] [99] [100] and Enceladus. [80] [101]

Mars, Enceladus and Europa are considered likely candidates in the search for life primarily because they may have underground liquid water, a molecule essential for life as we know it for its use as a solvent in cells. [39] Water on Mars is found frozen in its polar ice caps, and newly carved gullies recently observed on Mars suggest that liquid water may exist, at least transiently, on the planet's surface. [102] [103] At the Martian low temperatures and low pressure, liquid water is likely to be highly saline. [104] As for Europa and Enceladus, large global oceans of liquid water exist beneath these moons' icy outer crusts. [75] [96] [97] This water may be warmed to a liquid state by volcanic vents on the ocean floor, but the primary source of heat is probably tidal heating. [105] On 11 December 2013, NASA reported the detection of "clay-like minerals" (specifically, phyllosilicates), often associated with organic materials, on the icy crust of Europa. [106] The presence of the minerals may have been the result of a collision with an asteroid or comet according to the scientists. [106] Additionally, on 27 June 2018, astronomers reported the detection of complex macromolecular organics on Enceladus [107] and, according to NASA scientists in May 2011, "is emerging as the most habitable spot beyond Earth in the Solar System for life as we know it". [80] [101]

Another planetary body that could potentially sustain extraterrestrial life is Saturn's largest moon, Titan. [100] Titan has been described as having conditions similar to those of early Earth. [108] On its surface, scientists have discovered the first liquid lakes outside Earth, but these lakes seem to be composed of ethane and/or methane, not water. [109] Some scientists think it possible that these liquid hydrocarbons might take the place of water in living cells different from those on Earth. [110] [111] After Cassini data were studied, it was reported in March 2008 that Titan may also have an underground ocean composed of liquid water and ammonia. [112]

Phosphine has been detected in the atmosphere of the planet Venus. There are no known abiotic processes on the planet that could cause its presence. [113] Given that Venus has the hottest surface temperature of any planet in the solar system, Venusian life, if it exists, is most likely limited to extremophile microorganisms that float in the planet's upper atmosphere, where conditions are almost Earth-like. [114]

Measuring the ratio of hydrogen and methane levels on Mars may help determine the likelihood of life on Mars. [115] [116] According to the scientists, ". low H2/CH4 ratios (less than approximately 40) indicate that life is likely present and active." [115] Other scientists have recently reported methods of detecting hydrogen and methane in extraterrestrial atmospheres. [117] [118]

Complex organic compounds of life, including uracil, cytosine and thymine, have been formed in a laboratory under outer space conditions, using starting chemicals such as pyrimidine, found in meteorites. Pyrimidine, like polycyclic aromatic hydrocarbons (PAHs), is the most carbon-rich chemical found in the universe. [119]

The Rare Earth hypothesis postulates that multicellular life forms found on Earth may actually be more of a rarity than scientists assume. 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.

The systematic search for possible life outside Earth is a valid multidisciplinary scientific endeavor. [120] 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, [121] [122] and may be present even if there are no biological cells. [123]

Research outcomes Edit

As of 2019 [update] , no evidence of extraterrestrial life has been identified. [126] 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. [127] [128] [129]

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. [130] [131] [132]

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. [133] [134] However, NASA formally distanced itself from Hoover's claim. [135] 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." [136]

Extreme environments on Earth

On 17 March 2013, researchers reported that microbial life forms thrive in the Mariana Trench, the deepest spot on the Earth. [137] [138] Other researchers reported that microbes thrive inside rocks up to 1,900 feet (580 m) below the sea floor under 8,500 feet (2,600 m) of ocean off the coast of the northwestern United States. [137] [139] According to one of the researchers, "You can find microbes everywhere—they're extremely adaptable to conditions, and survive wherever they are." [137] Evidence of perchlorates have been found throughout the solar system, and specifically on Mars. Dr. Kennda Lynch discovered the first known instance of perchlorates and perchlorates-reducing microbes in a paleolake in Pilot Valley, Utah. [140] [141] These finds expand the potential habitability of certain niches of other planets.

In 2004, the spectral signature of methane ( CH
4 ) was detected in the Martian atmosphere by both Earth-based telescopes as well as by the Mars Express orbiter. Because of solar radiation and cosmic radiation, methane is predicted to disappear from the Martian atmosphere within several years, so the gas must be actively replenished in order to maintain the present concentration. [142] [143] On 7 June 2018, NASA announced a cyclical seasonal variation in atmospheric methane, which may be produced by geological or biological sources. [144] [145] [146] The European ExoMars Trace Gas Orbiter is currently measuring and mapping the atmospheric methane.

It is possible that some exoplanets may have moons with solid surfaces or liquid oceans that are hospitable. Most of the planets so far discovered outside the Solar System are hot gas giants thought to be inhospitable to life, so it is not yet known whether the Solar System, with a warm, rocky, metal-rich inner planet such as Earth, is of an aberrant composition. Improved detection methods and increased observation time will undoubtedly discover more planetary systems, and possibly some more like ours. For example, NASA's Kepler Mission seeks to discover Earth-sized planets around other stars by measuring minute changes in the star's light curve as the planet passes between the star and the spacecraft. Progress in infrared astronomy and submillimeter astronomy has revealed the constituents of other star systems.

Efforts to answer questions such as the abundance of potentially habitable planets in habitable zones and chemical precursors have had much success. Numerous extrasolar planets have been detected using the wobble method and transit method, showing that planets around other stars are more numerous than previously postulated. The first Earth-sized extrasolar planet to be discovered within its star's habitable zone is Gliese 581 c. [147]

Extremophiles Edit

Studying extremophiles is useful for understanding the possible origin of life on Earth as well as for finding the most likely candidates for future colonization of other planets. The aim is to detect those organisms that are able to survive space travel conditions and to maintain the proliferating capacity. The best candidates are extremophiles, since they have adapted to survive in different kind of extreme conditions on earth. During the course of evolution, extremophiles have developed various strategies to survive the different stress conditions of different extreme environments. These stress responses could also allow them to survive in harsh space conditions, although evolution also puts some restrictions on their use as analogues to extraterrestrial life. [148]

Thermophilic species G. thermantarcticus is a good example of a microorganism that could survive space travel. It is a bacterium of the spore-forming genus Bacillus. The formation of spores allows for it to survive extreme environments while still being able to restart cellular growth. It is capable of effectively protecting its DNA, membrane and proteins integrity in different extreme conditions (desiccation, temperatures up to -196 °C, UVC and C-ray radiation. ). It is also able to repair the damage produced by space environment.

By understanding how extremophilic organisms can survive the Earth's extreme environments, we can also understand how microorganisms could have survived space travel and how the panspermia hypothesis could be possible. [149]

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.

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. [150] The result was inconclusive, [151] and is still disputed by some scientists. [152] [153] [154] [155]

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. [156] However, he also considered that the conditions found on Mars were incompatible with carbon based life.

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. [157]

EXPOSE is a multi-user facility mounted in 2008 outside the International Space Station dedicated to astrobiology. [158] [159] 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. [160]

The Mars Science Laboratory (MSL) mission landed the Curiosity rover that is currently in operation on Mars. [161] It was launched 26 November 2011, and landed at Gale Crater on 6 August 2012. [45] Mission objectives are to help assess Mars' habitability and in doing so, determine whether Mars is or has ever been able to support life, [162] 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.

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. [163] 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. [163]

ExoMars is a robotic mission to Mars to search for possible biosignatures of Martian life, past or present. This astrobiological mission is currently under development by the European Space Agency (ESA) in partnership with the Russian Federal Space Agency (Roscosmos) it is planned for a 2022 launch. [164] [165] [166]

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. [167] 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. [168] [169]

Europa Clipper is a mission planned by NASA for a 2025 launch that will conduct detailed reconnaissance of Jupiter's moon Europa and will investigate whether its internal ocean could harbor conditions suitable for life. [170] [171] It will also aid in the selection of future landing sites. [172] [173]

Proposed concepts Edit

Icebreaker Life is a lander mission that proposed for NASA's Discovery Program for the 2021 launch opportunity, [174] 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. [175] [176] 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. [177] [178] [179]

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. [180] [181]

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. [182] [183] [184]

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. [185] 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. [186]

Explorer of Enceladus and Titan

Explorer of Enceladus and Titan (E 2 T) 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. [187]

Q&A: The 5 Ingredients Needed for Life Beyond Earth

A NASA scientist lists the essentials that extraterrestrial life must have to exist.

Back when astrogeophysicist Christopher McKay got his doctorate in 1982, the hunt for extraterrestrial life was confined to the solar system. The obvious places to look were the planets and moons that seemed most likely to be habitable: Mars, two moons of Saturn (Enceladus and Titan), and a moon of Jupiter called Europa.

That started to change in 1995, says McKay, a senior scientist at the NASA Ames Research Center, when astronomers began finding planets orbiting distant stars. These so-called exoplanets now number nearly 1,800, with one of the most Earth-like, the planet Kepler 186-f that orbits a red dwarf star known as Kepler 186, announced just this past April.

In a recent issue of the Proceedings of the National Academy of Sciences, McKay summarizes how the search for habitable planets needs to go beyond simply looking in the "Goldilocks zone"—the orbital distance where it's not too hot, not too cold, but just right for biology.

National Geographic spoke with McKay about how scientists can tell if an exoplanet is likely to be habitable, based on what is known about the range of environments that can support life on Earth.

In your PNAS paper, you talk about a "checklist for speculating on the possibilities of life on these distant worlds." What's on the list?

The first thing is temperature [i.e., temperature allowing for water in liquid form]. The astronomers know this—it's what defines the "habitable zone." But the next question you need to ask is whether water is actually present.

How do you determine whether a planet not only can have water, but does have water?

We need to have some measurement of the atmosphere to confirm that this isn't a planet that's lost all its water. You don't need much: One of the lessons of life on Earth is that a little water goes a long way. It's nice to have a Pacific Ocean, but you don't need it.

Once you know there's still some water on the planet, what do you need to know next?

Energy sources. Life on Earth uses only two types of energy for metabolism: sunlight and redox chemistry . One or the other has to be present, and if you're in the habitable zone of a star, you at least have enough light to support photosynthesis.

So you have the right temperature, water, and sunlight. What else do you need?

The next criterion is sort of a negative: Make sure there's nothing that will kill you, such as radiation.

That could be a real problem with a planet like Kepler 186-f, right? It orbits a red dwarf star, and those tend to have a lot of solar flares.

It's true that we humans are cream puffs when it comes to radiation. You know, a little excess sunlight and we get sunburns and skin cancer. But microbes, which are likely to be the first life-forms we find, are much, much tougher with respect to both UV and ionizing radiation.

You also list nitrogen as essential for habitability.

Yes, because life is almost certainly going to use amino acids, and it needs nitrogen to build them. So that's a key requirement.

OK, temperature, water, sunlight, nitrogen, and nothing that will kill off life. Anything else?

Yes: oxygen. It's not evidence of life directly—it's not the same as seeing the life-forms themselves. It's like seeing tire tracks when you're lost in the desert. It's not the car. It's not proof you're about to be rescued. But it's certainly damn interesting. And if the oxygen level is high enough, our experience on Earth leads us to suggest that that should enable complex life, plants and animals. And that's very cool.

So can we go out and search today for the things on your list?

Well, not with any [equipment] that's in space right now. None of the telescopes on the ground right now will do it either, I don't think. But there's no reason why everything on this list couldn't be checked off for Kepler 186-f and other Earth-size planets in the habitable zones of their stars within the next decade.

How about Mars? Is it even still worth looking for life there?

I have to admit my hope is dimming with the results that have come back from Curiosity and other missions. But it's not gone yet, partly because Mars is so close by that it [would] take a lot of negativity before I give up. It's like searching for your keys under the lamppost—you look there because that's where the light is good.

Even if we find life on Mars, though, there's another problem: The first assumption I would make is that, yeah, that's life, but it's directly related to us [because Earth and Mars are so close, any life found on Mars might have originated on Earth and been carried over on a meteorite—or vice versa, that life on Earth might have been carried over from Mars]. You'd have to prove that it isn't. If we find it 500 light-years away, on the other hand, we know it's not related.

You're still working on the search for life inside the solar system, though.

Yes, I'm working on a Europa mission concept, I'm working on an Enceladus mission concept, and I'm working on some Titan mission concepts. I'm working on Mars data coming back right now, and I'm working on future Mars missions. And now I've got a student who's going to be looking at Kepler 186-f, too. So I'm involved with all five of those worlds. I'm like a parent with many children. I love them all, and I resist saying that one is better than the other.

NASA's search for life

The ultimate goal of NASA's Exoplanet Program is to find unmistakable signs of current life.

Exoplanets&rsquo own skies could hold such signs, waiting to be revealed by detailed analysis of the atmospheres of planets well beyond our solar system.

When we analyze light shot by a star through the atmosphere of a distant planet, a technique known as transmission spectroscopy, the effect looks like a barcode. The slices missing from the light spectrum tell us which ingredients are present in the alien atmosphere. One pattern of black gaps might indicate methane, another, oxygen. Seeing those together could be a strong argument for the presence of life. Or we might read a barcode that shows the burning of hydrocarbons in other words, smog.

The danger (and the fungi on Venus)

In November 2019, Astrophysics & Space Science published Joseph&aposs paper, titled "Life on Venus and the interplanetary transfer of biota from Earth." 

The 18-page document proposes that Russia&aposs Venera 13 lander, which spent 127 minutes on the surface of Venus in 1982 before succumbing to extreme heat, had photographed images of organisms resembling lichen and fungi. Like his Mars work, Joseph&aposs review provides "evidence" of life via grainy digital images stretched, cropped and zoomed to oblivion, but notes "similarities in morphology are not proof of life." 

It&aposs the first and only example of a paper by Joseph to be published in a legitimate, peer-reviewed journal in the last decade. But following the controversy over the Mars paper, Joseph asked Astrophysics & Space Science to withdraw his Venus review and refund all publication costs, claiming that it publishes "fake articles." After I raised questions about the paper, Springer Nature said the Venus paper "will be carefully investigated following publishing best practice." It&aposs still available online and has been cited in at least one other scientific paper in a key space science journal. On June 23, after raising additional questions about the paper, an editor&aposs note was added. 

Over the last decade, Joseph and JOC have mostly been ignored by NASA and by the scientific community. Very few scientists take the alien fungi claims seriously, but Joseph&aposs work has been highlighted in UK tabloids, RT and many well-meaning science news sites since February 2019. Some have touted Joseph&aposs websites as "scientific journals" and even confused Joseph&aposs vanity website with legitimate, similarly named journals. One painted Joseph as someone trying to "defy the odds."

And that&aposs where the danger lies.

Astrobiology, the search for and study of extraterrestrial life, is a serious scientific endeavor. NASA has an astrobiology program, and searching for life is a critical part of its Mars exploration program. And although the public seems resistant to fanciful claims of fungal spores on Mars or lichen on Venus, they haven&apost gone away. If anything, social media seems to have made us more gullible. As crank, fringe theories start to gather steam in honest peer-reviewed journals, the public&aposs perception of astrobiology can quickly be muddied. 

"I feel like these guys have just poisoned the whole field," says Myers. 

Gil Levin, the scientist on Viking&aposs LR experiment, feels similarly. He published in Joseph&aposs JOC in 2010 and has a history with Joseph, who nominated the work for a Nobel prize. But in recent years, Levin has distanced himself. "He got to be so erratic that I was afraid to be associated with his work," he says. 

Joseph maintains that NASA has been infiltrated and is "controlled by religious fanatics" opposed to searching for extraterrestrial life. He claims he has ended his career "by discovering and documenting the obvious evidence of life on Mars" and says he can only wait for China to investigate the planet because NASA will "never tell the truth." 

An image taken by the Venera 13 lander from the surface of Venus.

Learning Materials

This video and accompanying guide is designed to help facilitate discussion and to provide tips for diving deeper into the world of Astrobiology. The activity is designed to enhance studies of various Life Science, Earth Science and Physical Science topics in middle school and high school such as: evolution proteins biogeology chemical reactions rocks and minerals the solar system and the universe. Relevant cross-cutting concepts include: Nature of Science Systems and System Models Interdependence of Science, Engineering and Technology. Click here to download the Video Discussion Guide (pdf).

Astrobiology: An Integrated Science Approach is a full-year integrated science curriculum that weaves its way through the disciplines of biology, chemistry, physics, astronomy, and Earth science, as well as sociology, ethics, and the psychology of human thought and behavior. The curriculum is intended to offer an entry into high-school science and was developed by the Technical Education Research Centers (TERC), an independent research-based non-profit organization.

Download free coloring pages from the NASA Astrobiology Program featuring the Perseverance rover. The artwork has been adapted from the Astrobiology Graphic Histories, and features moments in Perseverance’s mission to gather samples from the Martian surface at Jezero crater. Files are available as pdf files or png images. Dig out your markers, paints, and crayons and add some color to Perseverance’s journey!

Explore the possibility of finding life on other planets. See how NASA's search for water on Mars proved successful with the Phoenix Lander. Find out about extremophiles and what makes a habitable zone for life as we know it. Since the production of this video, NASA has learned more about Mars through these missions: Mars Reconnaissance Orbiter, Mars Science Laboratory (Curiosity), Mars Orbiter Mission, and MAVEN.

Learn about extremophiles and the hostile environments where they can be found through captivating NASA videos making up this 3rd-5th collection. Almost every possible environment on Earth is home to a living organism, no matter how hostile the environment may seem.

Where do we find extremophiles? We look for environments that push the limits for ordinary living organisms. NASA conducts analog testing in these extreme environments to better understand life on Earth and identify the potential for life in the universe.

Water in Extreme Environments engages youth in collaborative teams to engineer water filters with basic materials, and by playing a game to learn about where water can be found in our solar system.

Lead students in designing and building a mission to Mars with a guided education plan and resources from NASA, join in live stream Q&As with experts, and share student work with a worldwide audience. Learn how, why, and what Perseverance will explore on Mars, and find out about an exciting opportunity for you and your students to join in the adventure!

Download posters and digital wallpapers of some of astrobiology's greatest heroes! From exploring the depths of Earth's oceans to spotting worlds around distant starts, these heroes of astrobiology science are helping us understand life's origins on Earth and the potential for life in the Universe!

This educational product includes a set of trading cards featuring nine different extremophile groups. The front of each card has an image of an environment in which the extremophiles thrive (e.g. Grand Prismatic Spring at Yellowstone for the thermophiles). The back of each card has a small photo of a representational organism (e.g. Deinococcus radiodurans for the radioresistant microbes) and engaging text about each group’s “Extreme Abilities”, “Extreme Environments” and “Extreme Examples”. The trading cards were developed by the former NASA Astrobiology Institute (NAI) team at the University of Wisconsin, Madison.

A NASA-funded team of astrobiologists at the University of Maryland has contributed to classroom teaching kits available from Carolina Biologicals that focus on learning basic microbiology and related skills using an Archea, Halobacterium sp. NRC-1, as a model organism. Supporting the use of the kits are two other resources developed by by the astrobiologists, a genomic database of halophiles called HaloWeb with a companion education website, and an online resource about concepts in microbiology and molecular genetics called MolGenT.

Planetary Science Research Discoveries (PSRD) is a NASA-sponsored educational site sharing research on meteorites, asteroids, planets, moons, and other materials in our Solar System. Easily search through the extensive PSRD Archives for background reading and annotated slide sets for your online learning

access to everything from formal lesson plans to amazing imagery and stories about how NASA science and exploration are lifting our world. There will be ongoing opportunities to chat and interact with scientists directly.

This series of talks are presented by Charles Cockell, Professor of Astrobiology at the University of Edinburgh, Scotland, as casual, fireside chats for those who are isolated at home would like to learn about interesting questions in astrobiology. These informal talks are produced and presented by Charles Cockell, and are not supported by NASA Astrobiology. This link is provided as a resource of general interest to the astrobiology community. Any opinions expressed are the author’s alone.

If there were other life out there in the universe, how similar do you think it would it be to life on Earth? Would it use DNA as its genetic material, like you and me? Would it even be made up of cells? We can only speculate about these questions, since we haven't yet found any life forms that hail from off of Earth. But we can think in a more informed way about whether life might exist on other planets (and under what conditions) by considering how life may have arisen right here on our own planet. In this article, we'll examine scientific ideas about the origin of life on Earth. The when of life's origins is well-supported by fossils and radiometric dating. But the how is much less understood.

Earth Analogues for Possible Life on Mars: Lessons and Activities

As the number of “potentially habitable” planets that astronomers find continues to rise, we seem ever closer to answering the question, “Are we alone in the universe?” But should we be looking for life elsewhere? If we were to find life in one of these worlds, should we try to contact any beings who may live there? Is that wise? Aomawa Shields navigates the murky waters of pursuing curiosity in this video. A review quiz is also provided.

A collection of materials from the Woods Hole Oceanographic Institution released for the celebration of the 50th Anniversary of the Alvin submersible.

Dive and Discover is an interactive website designed to immerse you in the excitement of discovery and exploration of the deep seafloor. There are a number of virtual expeditions of particular relevance to astrobiology, including sections on hydrothermal vents on the ocean floor.

A new set of Astrobiology lesson plans for K-12 classrooms from Albion College. In this collection of science activities, seven thorough lesson plans regarding distinct topics in Astrobiology are presented. Each lesson plan has direct and descriptive rationale, objectives, materials, instructions, assessments, reflections, standards, grade levels, and evaluations.

Stromatolites are one of the oldest ecosystems on Earth. These structures are made by the activities of microbes. This video provides some basic insight into living examples of these ancient microbial ecosystems.

Through the NASA Astrobiology Institute (NAI), the NASA Astrobiology Program supported the development of an educational game called Life Underground at the University of Southern California’s School of Cinematic Arts. Life Underground is an interactive outreach experience for 7th and 8th grade classrooms. The goal is for students to visualize microscopic life at a range of terrestrial and extraterrestrial subsurface conditions. Students take the role of a young scientist investigating extreme subsurface environments for microbial life. Tested by teachers, Life Underground was carefully designed to deliver the excitement of astrobiology exploration into middle school classrooms and inspire players to explore STEM-based careers.

The quest to understand our beginnings — of our universe, of life on Earth, of our species — inspires people all over the world. At the University of Wisconsin–Madison, researchers have forged partnerships with colleagues in South Africa and are uncovering answers and opening new scientific frontiers.

The story of oceans is the story of life. Oceans define our home planet, covering the majority of Earth’s surface and driving the water cycle that dominates our land and atmosphere. But more profound still, the story of our oceans envelops our home in a far larger context that reaches deep into the universe and places us in a rich family of ocean worlds that span our solar system and beyond.

NSF-produced audio documentary envisions future where scientists can predict how cells, brains, bodies and biomes will react to changing environments.

The Mission: Find Life! exhibit at the Pacific Science Center in Seattle, WA shows how astrobiologists search for life elsewhere in the Universe, studying extreme environments to understand the potential habitability of extraterrestrial environments and examining how life might arise on planets orbiting stars different from our Sun. The exhibit features research at the Virtual Planetary Laboratory and runs March 18-September 4, 2017. Videos from the exhibit can be viewed from this link.

Get set for launch. “Eyes on Exoplanets” will fly you to any planet you wish—as long as it's far beyond our solar system. This fully rendered 3D universe is scientifically accurate, allowing you to zoom in for a close look at more than 1,000 exotic planets known to orbit distant stars.

Astronomy is a textbook published by OpenStax, a national non-profit project to develop high-quality intro textbooks free to students. Senior authors are Andrew Fraknoi, David Morrison, and Sidney Wolff. The project had the help of over 75 astronomers and astronomy educators, to make sure that the text is up-to-date, authoritative, and educationally sound. Ancillary materials are being developed. Authors and instructors can share syllabi, teaching materials, handouts, labs, etc. at the Open Education Resources (OER) Commons website:

A resource guide to exploring eclipses in general and the August 21, 2017 Total Eclipse.

A listing of resources about cultures and astronomy by Andrew Fraknoi

A series of fun, easy to understand, science animation videos on topics such as: Are You Alone? (In the Universe), the Big Bang, the Fermi Paradox, What is Life, and much more.

Rising Stargirls announces the release of their new Teaching and Activity Handbook! By integrating creative strategies such as free writing, visual art, and theater exercises, this new innovative astronomy curriculum addresses each girl as a whole by providing an avenue for individual self-expression and personal exploration that is interwoven with scientific engagement and discovery. Hands-on activities, educator resources, and a suggested structure for workshops are provided in this manual. It is meant for use it in classrooms and informal learning environments anywhere in the world. The activities are created for middle-school girls, ages 10-15.

With gorgeous graphics, supporting background reading, and three inquiry- and standards-based, field tested activities, this poster is a great addition to any middle or high school classroom. It explores the connection between extreme environments on Earth, and potentially habitable environments elsewhere in the Solar System.

In December 2011, high in the central Andes of Chile, NASA scientists launched the prototype Planetary Lake Lander, a testing platform for the development of robots that are capable of making scientific decisions based on the data they collect. Dr. Nathalie Cabrol leads a team of researchers working on these smart robots, which will expand our ability to search for life in the universe.

The Search for the Origin of Life takes a personal look at scientists around the United States working with the NASA Astrobiology Institute (NAI) to understand the origin of life. Attempting the seemingly impossible, these researchers want to answer one of humanity's oldest questions - how did life begin? Travel with them to some of our planet Earth's most extreme environments - from the frozen glaciers of the Canadian Arctic, to the inhospitable thermal springs of Yellowstone National Park, and to mysterious caves in Italy.

Astrobiobound gives middle and high school students an opportunity to take a crack at planning an astrobiology-specific NASA science mission to Mars, helping them to learn how science and systems engineering play a part in achieving their goal.

Learn about important events in the history of life on Earth.

The Solar System Treks are online, browser-based portals that allow you to visualize, explore, and analyze the surfaces of other worlds using real data returned from a growing fleet of spacecraft.

In the framework of the program Europlanet 2012, six Solar System bodies are mapped by planetary scientists and graphic artists on spectacular map pages.

NAI scientists and their international partners are featured in this documentary which has aired both on PBS and NASA-TV. The program highlights cutting edge field work looking at unique habitats and survival mechanisms of life on Earth.

This is an integrated science curriculum for ninth or tenth grade based on the theme of evolution and delivered on CD-ROM. It’s six modules span the breadth of astrobiology research, from cosmic evolution through the evolution of life, and beyond.

WAMC’s radio program "To The Best Of Our Knowledge", NAI Principal Investigator Doug Whittet talks about astrobiology, and the ongoing research and education activities of his New York Center for Astrobiology (NYCA), seated at RPI.

NOVA’s ScienceNOW series, hosted by Neil de Grasse Tyson, released an episode called Hunt for Alien Earths devoted to the work of astronomers who search for planets orbiting other stars that might host life.

Tune into this podcast from Omega Tau, a wide-reaching series from Stuttgart, Germany, for an interview with NAI’s Director Carl Pilcher. He gives a great introduction to the NAI, astrobiology, and the search for life elsewhere in the Universe.

NASA’s Planet Quest website presents a Historic Timeline of the search for other worlds.

CLASSROOM MATERIALScience Fiction Stories with Good Astronomy & Physics Prof. Andrew Fraknoi (Foothill College) has compiled a selective list of short stories and novels that use more or less accurate science and can be used for teaching or reinforcing astronomy or physics concepts.

These are topic based, educationally rich, experiences that are captured during real expeditions with scientists doing current research in the field.

This booklet contains five inquiry- and standards-based classroom activities for grades 5-8 and three math extensions spanning topics from Defining Life, to Determining the Chances of Extraterrestrial Life.

Tune in to this YouTube video produced by Oort Kuiper in 2008 for a six-minute journey through astrobiology!

Watch John Delanos TEDx talk about a survey of astrobiology research topics masterfully conveyed as a “story of us.” The talk ranges from the manufacture of organic molecules in space to extrasolar planets, to hyperthermophilichemolithoautotrophs!

Out of billions of galaxies and billions of stars, how do we find Earth-like habitable worlds? What is essential to support life as we know it? In this TED Ed video, astrobiologist Ariel Anbar provides a checklist for finding life on other planets.

Combining startling animation with input from expert astrophysicists and astrobiologists, Alien Planets Revealed takes viewers on a journey along with the Kepler telescope.

This hands-on/minds-on lesson can engage learners in a variety of settings, showing them how scientists use Earth-based bacteria to investigate the potential for life on Mars.

NASA’s Cassini mission captured dazzling imagery of Saturn’s moon Enceladus, detailing plumes of ice particles and water vapor erupting from the surface and extending hundreds of kilometers into space making it an object of astrobiological study.

You can now display images of the intriguing world of Titan in your classroom, office, or home! In addition to the beautiful image on the front of the poster, there are lesson plans and background reading on the back.

Microbial Life is a freely accessible digital library dedicated to the diversity, ecology, and evolution of the microbial world. Engage students with hands-on activities and other curriculum-based resources that cover astrobiological topics.

The PlanetQuest group at JPL created these amazing posters, beckoning us to consider places beyond our imagination – beyond our Solar System!

In celebration of the 2015 International Year of Light, a new international exhibition, "LIGHT: Beyond the Bulb" has been launched by the same group that created “From Earth to the Universe”.

TIMETREE is a public resource for knowledge on the timescale and evolutionary history of life.

Interested in using astrobiology to teach math? Already teaching astrobiology and want to bring in some math problem sets? The Astrobiology Math booklet was developed by Dr. Sten Odenwald at NASA as part of the Space Math at NASA project.

The Big Picture Science radio show, produced by the SETI Institute, takes listeners on a journey with modern science research through lively and intelligent storytelling. A special astrobiology collection is available.

Nova has combined the latest telescope images with dazzling animation, immersing audiences in the sights and sounds of alien worlds. Astrobiologists explain how these places are changing how we think about the potential for life in our solar system.

Sign-up to get the latest in news, events, and opportunities from the NASA Astrobiology Program.

What Might Life on Other Planets Look Like? A Harvard Biologist Explains

Jonathan B. Losos is a biology professor and director of the Losos Laboratory at Harvard University and Curator of Herpetology at Harvard&rsquos Museum of Comparative Zoology. His research regularly appears in top scientific journals, such as Nature and Science, and he has written a popular series about his work for The New York Times. Losos is the editor in chief of The Princeton Guide to Evolution and a member of the National Geographic Society&rsquos Committee for Research and Exploration. He is the author of Lizards in an Evolutionary Tree: Ecology and Adaptive Radiation of Anoles.

Jonathan B. Losos: So this question about the inevitability of evolution, the extent to which the outcomes we see in the world today were destined to occur, has a number of implications.

I mean just most generally it tells us whether how fated evolution was to occur, how the outcome today was destined in a way.

But it has other implications as well that people have long speculated about, and that is: what would life be like on other planets if it is evolved? Would it be like the world today here on Earth or would it be completely different?

And this question has taken on some increased urgency or at least interest in recent years because we now realize that there are many planets out there that are like Earth. We used to think that Earth was perhaps unique and so perhaps life as we know it is unique, because we&rsquore the only place that it could evolve.

But quite the contrary we&rsquove now discovered that there are lots of what are called &ldquohabitable exoplanets&rdquo, Some people estimate millions, even billions just in our own Milky Way galaxy. So if that&rsquos the case, if there are that many Earth-like planets &ndash and by Earth-like I mean about the same size, temperature, atmosphere somewhat similar, running water &ndash roughly similar conditions. If there are really that many Earth-like planets many people think that it&rsquos very likely that life has evolved on them.

And so the question is what will that life look like? Well there are those who argue that from the argument of convergent evolution they argue that species facing the same conditions here on Earth evolved the same solutions by natural selection.

They extrapolate to say if conditions on other planets are similar to here then we would see very similar lifeforms, that you arrive on whatever planet you&rsquoll see animal and plant-like organisms that look very familiar. Some people have gone so far as to say that, in fact, human type organisms, humanoids will occur on other planets. So there will be intelligent beings that if we saw them they would be recognizable which, of course, is what Hollywood tells us. If you watch almost any science fiction TV show or movie the intelligent lifeform is bipedal, a couple of arms, a mouth. Maybe they only have three fingers and pointy ears and they&rsquore green, but they&rsquore pretty humanoid.

And so some people say yes, that&rsquos actually very likely that humans are a very successful lifeform here on Earth that we are extremely well adapted to our environment which ancestrally was occurring on the plains of Africa. But we have adapted so exquisitely that we now dominate the world. And so if this is such a good adaptation here on Earth it would similarly be a good adaptation on another planet and evolution would be likely to take the similar course. That is the argument that is being made in some quarters.

Not everyone is convinced by this argument that evolution is deterministic. We recognize that convergent evolution does occur more than we used to realize but still it is argued and I agree with this viewpoint, it&rsquos not inevitable. And the reason is that there are often multiple ways to adapt to the same environmental circumstance. And so even though species are faced with the same conditions they may find different ways to adapt to them. And my favorite example of that has to do with a bird that everyone knows &ndash the woodpecker. And everyone&rsquos heard the tat-tat-tat of a woodpecker on a tree or on your garage siding or whatever. People don&rsquot actually know what the woodpecker is doing.

This is what the woodpecker is doing: It is using its beak to pound on dead wood, listening for a hollow space, the echo indicating there&rsquos a hollow space in the wood which is where a grub, a larval beetle or some other insect is eating the dead wood. And so it listens for the sound of a hollow space. When it hears it, it then starts tapping very hard &ndash tat-tat-tat-tat-tat-tat &ndash using its beak as a jackhammer to dig into the, to chisel or to dig into the deep wood to get to the tunnel. Once it&rsquos there&mdashthe woodpecker has an extremely long tongue. So long, in fact, that it wraps around its brain case. But it sticks out this long tongue that has little prickles on it, and the tongue goes in and it snags the grub which looks like a mealworm or a &ndash snags the grub and pulls it out and eats it. And that is how they capture the food that they eat.

Well woodpeckers are found on almost every continent in the world. They&rsquore very successful, but they don&rsquot fly very well across water. They don&rsquot like to fly across water. And so isolated islands tend not to have woodpeckers. And in their absence other species have evolved to fill the same niche.

And the most extreme example of a different way of doing the same thing is an animal on the island of Madagascar called an aye-aye. Now an aye-aye is a type of lemur. Now people know lemurs from the TV show Zooboomafoo and maybe they&rsquove seen them, the ring-tailed lemur. They hop around, very cute, and so on.

The aye-aye is not very cute. It&rsquos about the size maybe of a small housecat and it&rsquos kind of demonic looking. It has these big leathery ears and these bright yellow eyes and a face that only a mother can love. And the native people of Madagascar had all kinds of taboos and myths about them because they look &ndash and they only come out at night. But their most extreme feature that I think really kind of freaks people out is that their third finger is long and extremely thin. It looks skeletal, and it can rotate in any direction. It&rsquos this kind of finger that can wiggle around.

Anyway, they live the same lifestyle as a woodpecker. They&rsquore looking for the same grubs in dead wood. But they do it in a completely different way. Instead of tapping with their peak they tap with their finger. They go around the wood going tap-tap-tap and their big ears are rotated forward listening for the sound of an echo.

And when they hear the echo of an empty tunnel they have these teeth that are &ndash these teeth are kind of sticking out like this, these chiseling incisors that are very strong. And they bite their way through the wood and bite into the wood until they get the tunnel. And then once they get there they then use their finger again. They stick it in there and they snag the larvae and pull it out. And so they&rsquore doing exactly the same thing that the woodpecker is doing but they&rsquove evolved a completely different set of adaptations. And so that&rsquos just one example of how species can adapt to do the same thing in very different ways.

And we see many examples of that in the world. Conversely we also see many examples of species that have no evolutionary parallel. What we call an evolutionary singleton. That is a species that is very well adapted to where it lives but no other species has done the same thing. And my favorite example of that is the duck-billed platypus, this extraordinary animal in Australia. Now people like to make fun of the platypus but they don&rsquot realize that the platypus is exquisitely adapted to living in the streams in eastern Australia. And so it has very lush fur that allows it to swim in water that&rsquos basically almost at freezing It has a powerful tail It&rsquos got webbed feet for swimming And then most extraordinarily it has this duck bill. Now it&rsquos not actually &ndash it kind of looks like a duck&rsquos bill, but it&rsquos not hard like a duck&rsquos bill.It&rsquos actually leathery.

But more importantly it&rsquos covered with thousands of little receptors and these receptors there&rsquos two types of them. One of them can detect slight variation in ripples of water. And so if something goes swimming by they can detect it in the water But in addition they have electro receptors. They can detect very slight electrical discharges. And so when an animal moves its muscles there&rsquos a little bit of electrical activity, and the platypus can detect that. And so when it&rsquos swimming under water it closes its eyes, its ears and its mouth, but based on the receptors on its bill it can find its way around and it can locate its prey&mdashRemarkable adaptation to eating crayfish and other food items like that.

Well so, the platypus lives in these streams that are in no way remarkable. There are streams like that behind the house I grew up in in St. Louis and they occur around the world. Yet nowhere else has a duck-billed platypus evolved. Why is it that it evolved in Australia and nowhere else? Well there are many examples of species extremely well-adapted but no parallel. Things like the chameleon, elephants, giraffes, many types of plants. Many evolutionary singletons. In fact, humans are an evolutionary singleton. If we are so well adapted to our environment, why didn&rsquot something like us evolve anywhere else in the world? Why didn&rsquot they evolve on Madagascar or in South America where monkeys colonized 40 million years ago?

And so this is the counterpart to the argument of evolutionary determinism and convergence. We could probably make a list just as long of species that have not converged. And so in many cases species &ndash in many cases evolution seemed not to be deterministic. That problems posed by environment may elicit different evolutionary solutions.

Human beings tend think that we—as a species—are very special. We dominate this planet that we're on, mostly due to our collective intelligence and ability to adapt to this particular climate. But Harvard biologist Jonathan B. Losos has an interesting theory that since there are so many Earth-type planets in our galaxy alone it's possible that there's some humanoid looking (at least in the bipedal sense) creatures out there, too. In fact, he posits, they might not even be that far off from the kind we're used to seeing in Hollywood movies. But he also dips into convergent evolutions, and presents the opposite side of the argument: evolutionary singletons. If you're interested in learning more, Jonathan's new book is called Improbable Destinies: Fate, Chance, and the Future of Evolution.

Intelligent life probably exists on distant planets — even if we can’t make contact, astrophysicist says

Recently released Navy videos of what the U.S. government now classifies as “unidentified aerial phenomena” have set off another round of speculative musings on the possibility of aliens visiting our planet. Like other astrophysicists who have weighed in on these sightings, I’m skeptical of their extraterrestrial origins. I am confident, however, that intelligent life-forms inhabit planets elsewhere in the universe. Math and physics point to this likely conclusion. But I think we’re unlikely to be able to communicate or interact with them — at least in our lifetimes.

Wanting to understand what’s “out there” is a timeless human drive, one that I understand well. Growing up in poorer and rougher neighborhoods of Watts, Houston’s Third Ward and the Ninth Ward of New Orleans, I was always intrigued by the night sky even if I couldn’t see it very easily given big-city lights and smog. And for the sake of my survival, I didn’t want to be caught staring off into space. Celestial navigation wasn’t going to help me find my way home without getting beaten up or shaken down.

From early childhood, I compulsively and continuously counted the objects in my environment — partly to soothe my anxieties and partly to unlock the mysteries inside things by enumerating them. This habit earned me nothing but taunts and bullying in my hood where, as a bookish kid, I was already a soft target. But whenever I looked up at a moonless night sky, I wondered how I might one day count the stars.

By age 10, I’d become fascinated, even obsessed, with Einstein’s theory of relativity and the quantum possibilities for the multiple dimensions of the universe it opened up in my mind. By high school, I was winning statewide science fairs by plotting the effects of special relativity on a first-generation desktop computer.

So perhaps it’s not surprising that I have gone on to spend much of my career working with other astrophysicists to develop telescopes and detectors that peer into the remote reaches of space and measure the structure and evolution of our universe. The international Dark Energy Survey collaboration has been mapping hundreds of millions of galaxies, detecting thousands of supernovae, and finding patterns of cosmic structure that reveal the nature of dark energy that is accelerating the expansion of our universe. Meanwhile, the Legacy Survey of Space and Time will make trillions of observations of 20 billion stars in the Milky Way.

What we’re discovering is that the cosmos is much vaster than we ever imagined. According to our best estimate, the universe is home to a hundred billion trillion stars — most of which have planets revolving around them. This newly revealed trove of orbiting exoplanets greatly improves the odds of our discovering advanced extraterrestrial life.

Scientific evidence from astrobiology suggests that simple life — composed of individual cells, or small multicellular organisms — is ubiquitous in the universe. It has probably occurred multiple times in our own solar system. But the presence of humanlike, technologically advanced life-forms is a much tougher proposition to prove. It’s all a matter of solar energy. The first simple life on Earth probably began underwater and in the absence of oxygen and light — conditions that are not that difficult to achieve. But what enabled the evolution of advanced, complex life on Earth was its adaptation to the energy of the sun’s light for photosynthesis. Photosynthesis created the abundant oxygen on which high life-forms rely.

It helps that Earth’s atmosphere is transparent to visible light. On most planets, atmospheres are thick, absorbing light before it reaches the surface — like on Venus. Or, like Mercury, they have no atmosphere at all. Earth maintains its thin atmosphere because it spins quickly and has a liquid iron core, conditions that lead to our strong and protective magnetic field. This magnetosphere, in the region above the ionosphere, shields all life on Earth, and its atmosphere, from damaging solar winds and the corrosive effects of solar radiation. That combination of planetary conditions is difficult to replicate.

Still, I’m optimistic that there have been Cambrian explosions of life on other planets similar to what occurred on Earth some 541 million years ago, spawning a cornucopia of biodiversity that is preserved in the fossil record. The more expert we become in observing and calculating the outer reaches of the cosmos, and the more we understand about how many galaxies, stars and exoplanets exist, the greater the possibility of there being intelligent life on one of those planets.

Extraterrestrial Evolution

If an alien has undergone natural selection and has multiple functional parts (such as sensory systems, limbs, internal organs) Levin and his coauthors posit that they must have undergone major evolutionary transitions, in which a group of individuals that could replicate independently (such as cells) cooperate to create a complex life form.

This means complex aliens will likely be entities made up of many smaller entities, with mechanisms that maintain cooperation to keep the organism functioning. This would be similar to what we see among the billions of cells in our own bodies. On planets that have experienced more major transitions than our own, this could even mean nested societies, where social colonies collaborate by specializing in different tasks on a planet-wide scale.

‘We still can’t say whether aliens will walk on two legs or have big green eyes,” Levin said. “But we believe evolutionary theory offers a unique additional tool for trying to understand what aliens will be like, and we have shown some examples of the kinds of strong predictions we can make with it.”

Watch the video: Αναζητώντας ζωή σε άλλους πλανήτες (December 2022).