Planetary habitability

2317:, that orbit their stars in circular orbits far enough away from the habitable zone not to disturb it but close enough to "protect" terrestrial planets in closer orbit in two critical ways. First, they help to stabilize the orbits, and thereby the climates of the inner planets. Second, they keep the inner stellar system relatively free of comets and asteroids that could cause devastating impacts. Jupiter orbits the Sun at about five times the distance between the Earth and the Sun. This is the rough distance we should expect to find good Jupiters elsewhere. Jupiter's "caretaker" role was dramatically illustrated in 1994 when 661: 29: 1855: 1904:(such a world would have a year lasting just 6.3 days). At those distances, the star's gravity would cause tidal locking. One side of the planet would eternally face the star, while the other would always face away from it. The only ways in which potential life could avoid either an inferno or a deep freeze would be if the planet had an atmosphere thick enough to transfer the star's heat from the day side to the night side, or if there was a gas giant in the habitable zone, with a 10947: 8297: 1093: 1916: 889:

Mars and that of Earth or Venus: 0.3 Earth masses has been offered as a rough dividing line for habitable planets. However, a 2008 study by the Harvard-Smithsonian Center for Astrophysics suggests that the dividing line may be higher. Earth may in fact lie on the lower boundary of habitability: if it were any smaller, plate tectonics would be impossible. Venus, which has 85% of Earth's mass, shows no signs of tectonic activity. Conversely, "

10875: 1832:, the nearest star system to the Sun, suggested that binaries need not be discounted in the search for habitable planets. Centauri A and B have an 11 AU distance at closest approach (23 AU mean), and both should have stable habitable zones. A study of long-term orbital stability for simulated planets within the system shows that planets within approximately three AU of either star may remain rather stable (i.e. the 7402: 10911: 1085: 10935: 8309: 728:, including 54 that may be in the habitable zone. Six of the candidates in this zone are smaller than twice the size of Earth. A more recent study found that one of these candidates (KOI 326.01) is much larger and hotter than first reported. Based on the findings, the Kepler team estimated there to be "at least 50 billion planets in the Milky Way" of which "at least 500 million" are in the habitable zone. 10887: 984:

planets has surprised most researchers: 90% have an orbital eccentricity greater than that found within the Solar System, and the average is fully 0.25. This means that the vast majority of planets have highly eccentric orbits and of these, even if their average distance from their star is deemed to be within the HZ, they nonetheless would be spending only a small portion of their time within the zone.

1817:, for example). However, where the separation is significantly less, a stable orbit may be impossible. If a planet's distance to its primary exceeds about one fifth of the closest approach of the other star, orbital stability is not guaranteed. Whether planets might form in binaries at all had long been unclear, given that gravitational forces might interfere with planet formation. Theoretical work by 7169: 10923: 2658:) and we should expect to find planets throughout the galaxy between two and twelve Earth masses. If the star system is otherwise favorable, such planets would be good candidates for life as they would be large enough to remain internally dynamic and to retain an atmosphere for billions of years but not so large as to accrete a gaseous shell which limits the possibility of life formation. 10899: 1957:, has shown that seawater, too, could be effectively circulated without freezing solid if the ocean basins were deep enough to allow free flow beneath the night side's ice cap. Further research—including a consideration of the amount of photosynthetically active radiation—suggested that tidally locked planets in red dwarf systems might at least be habitable for higher plants. 1335: 9410: 1003:, seasons will not occur and a main stimulant to biospheric dynamism will disappear. The planet would also be colder than it would be with a significant tilt: when the greatest intensity of radiation is always within a few degrees of the equator, warm weather cannot move poleward and a planet's climate becomes dominated by colder polar weather systems. 4335:

Jenkins, Jon M.; Latham, David W.; Lissauer, Jack J.; Marcy, Geoffrey W.; Rowe, Jason; Sasselov, Dimitar; Boss, Alan; Charbonneau, David; Ciardi, David; Doyle, Laurance; Dupree, Andrea K.; Ford, Eric B.; Fortney, Jonathan; et al. (2011). "Characteristics of planetary candidates observed by Kepler, II: Analysis of the first four months of data".

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longer, because red dwarf stars live for hundreds of billions of years or even longer on the main sequence. However, combined with the above disadvantages, it is more likely that red dwarf stars would remain habitable longer to microbes, while the shorter-lived yellow dwarf stars, like the Sun, would remain habitable longer to animals.

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to only last roughly the first 1.2 billion years of its existence. If a planet forms far away from a red dwarf so as to avoid tidal locking, and then migrates into the star's habitable zone after this turbulent initial period, it is possible that life may have a chance to develop. However, observations of the 7 to 12-billion year old

1281:, and water, are gaseous at warm temperatures. In the hot region close to the Sun, these volatile compounds could not have played a significant role in the planets' geological formation. Instead, they were trapped as gases underneath the newly formed crusts, which were largely made of rocky, involatile compounds such as 1096: 1095: 1101: 1099: 1094: 2042:

sequence) within the former massive-star system may be enriched with the relatively large supply of the heavy elements so close to a supernova explosion. However, this states nothing about what types of planets would form as a result of the supernova material, or what their habitability potential would be.

776: 1100: 1806:. This may be partly sample bias, as massive and bright stars tend to be in binaries and these are most easily observed and catalogued; a more precise analysis has suggested that the more common fainter stars are usually singular, and that up to two thirds of all stellar systems are therefore solitary. 2352:

above. However, during the process of migrating into a habitable zone, a Jupiter-size planet may capture a terrestrial planet as a moon. Even if such a planet is initially loosely bound and following a strongly inclined orbit, gravitational interactions with the star can stabilize the new moon into a

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While stellar crowding proves disadvantageous to habitability, so too does extreme isolation. A star as metal-rich as the Sun would probably not have formed in the very outermost regions of the Milky Way given a decline in the relative abundance of metals and a general lack of star formation. Thus, a

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While the likelihood of finding a planet in the habitable zone around any specific red dwarf is slight, the total amount of habitable zone around all red dwarfs combined is equal to the total amount around Sun-like stars given their ubiquity. Furthermore, this total amount of habitable zone will last

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A "stable" HZ implies two factors. First, the range of an HZ should not vary greatly over time. All stars increase in luminosity as they age, and a given HZ thus migrates outwards, but if this happens too quickly (for example, with a super-massive star) planets may only have a brief window inside the

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into a core group of 17,000 potentially habitable stars, and the selection criteria that were used provide a good starting point for understanding which astrophysical factors are necessary for habitable planets. According to research published in August 2015, very large galaxies may be more favorable

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Ward and Brownlee emphasize that such impacts ought to be rare, reducing the probability of other Earth-Moon type systems and hence the probability of other habitable planets. Other moon formation processes are possible, however, and the proposition that a planet may be habitable in the absence of a

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For a planet around a red dwarf star to support life, it would require a rapidly rotating magnetic field to protect it from the flares. A tidally locked planet rotates only very slowly, and so cannot produce a geodynamo at its core. The violent flaring period of a red dwarf's life cycle is estimated

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Thus, while there is reason to suspect that the four "life elements" ought to be readily available elsewhere, a habitable system probably also requires a supply of long-term orbiting bodies to seed inner planets. Without comets there is a possibility that life as we know it would not exist on Earth.

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A larger planet is likely to have a more massive atmosphere. A combination of higher escape velocity to retain lighter atoms, and extensive outgassing from enhanced plate tectonics may greatly increase the atmospheric pressure and temperature at the surface compared to Earth. The enhanced greenhouse

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are common to all stars, but the severity of such fluctuations covers a broad range. Most stars are relatively stable, but a significant minority of variable stars often undergo sudden and intense increases in luminosity and consequently in the amount of energy radiated toward bodies in orbit. These

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vaporize the whole water reservoir and, as a second effect, induce the photodissociation of water vapor and the loss of hydrogen to space. The outer edge of the HZ is the distance from the star where a maximum greenhouse effect fails to keep the surface of the planet above the freezing point, and by

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in 1959, based on climatic constraints imposed by the host star. After an energy source, liquid water is widely considered the most important ingredient for life, considering how integral it is to all life systems on Earth. However, if life is discovered in the absence of water, the definition of an

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A 2020 study found that about half of Sun-like stars could host rocky, potentially habitable planets. Specifically, they estimated with that, on average, the nearest habitable zone planet around G and K-type stars is about 6 parsecs away, and there are about 4 rocky planets around G and K-type stars

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on Earth approximately 500 million years after the planet's formation. "A" class stars (which shine for between 600 million and 1.2 billion years) and the very latest of the "B" class stars (which shine 10+ million to 600 million) fall within this window. At least theoretically life could emerge in

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orbits and enabled many to cross Earth's orbit and supply the planet with important volatiles such as water and carbon dioxide. Before Earth reached half its present mass, icy bodies from the Jupiter–Saturn region and small bodies from the primordial asteroid belt supplied water to the Earth due to

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Thus, relative isolation is ultimately what a life-bearing system needs. If the Sun were crowded amongst other systems, the chance of being fatally close to dangerous radiation sources would increase significantly. Further, close neighbors might disrupt the stability of various orbiting bodies such

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rather than photosynthesis, for instance, which would be possible in a red dwarf system. A static primary star position removes the need for plants to steer leaves toward the sun, deal with changing shade/sun patterns, or change from photosynthesis to stored energy during night. Because of the lack

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In determining the feasibility of extraterrestrial life, astronomers had long focused their attention on stars like the Sun. However, since planetary systems that resemble the Solar System are proving to be rare, they have begun to explore the possibility that life might form in systems very unlike

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elements within a planet's core is the other significant component of planetary heating). Mars, by contrast, is nearly (or perhaps totally) geologically dead and has lost much of its atmosphere. Thus it would be fair to infer that the lower mass limit for habitability lies somewhere between that of

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has suggested a "living worlds hypothesis" in which our understanding of what constitutes habitability cannot be separated from life already extant on a planet. Planets that are geologically and meteorologically alive are much more likely to be biologically alive as well and "a planet and its life

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that can dim their emitted light by up to 40% for months at a time, while at other times they emit gigantic flares that can double their brightness in a matter of minutes. Such variation would be very damaging for life, as it would not only destroy any complex organic molecules that could possibly

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One important qualification to habitability criteria is that only a tiny portion of a planet is required to support life, a so-called Goldilocks Edge or Great Prebiotic Spot. Astrobiologists often concern themselves with "micro-environments", noting that "we lack a fundamental understanding of how

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of the planet's main biotic solvent (e.g., water on Earth). If, for example, Earth's oceans were alternately boiling and freezing solid, it is difficult to imagine life as we know it having evolved. The more complex the organism, the greater the temperature sensitivity. The Earth's orbit is almost

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and complex metazoans (animals). Unicellularity necessarily precedes multicellularity in any hypothetical tree of life, and where single-celled organisms do emerge there is no assurance that greater complexity will then develop. The planetary characteristics listed below are considered crucial for

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have been found to date confirm the relationship between high metal content and planet formation: "Stars with planets, or at least with planets similar to the ones we are finding today, are clearly more metal rich than stars without planetary companions." This relationship between high metallicity

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Borucki, William J.; Koch, David G.; Basri, Gibor; Batalha, Natalie; Brown, Timothy M.; Bryson, Stephen T.; Caldwell, Douglas; Christensen-Dalsgaard, Jørgen; Cochran, William D.; Devore, Edna; Dunham, Edward W.; Gautier, Thomas N.; Geary, John C.; Gilliland, Ronald; Gould, Alan; Howell, Steve B.;

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The exact effects of these changes can only be computer modelled at present, and studies have shown that even extreme tilts of up to 85 degrees do not absolutely preclude life "provided it does not occupy continental surfaces plagued seasonally by the highest temperature." Not only the mean axial

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In 2020, a computer simulation of the evolution of planetary climates over 3 billion years suggested that feedbacks are a necessary but not a sufficient condition for preventing planets from ever becoming too hot or cold for life, and that chance also plays a crucial role. Related considerations

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Size is not the only factor in making red dwarfs potentially unsuitable for life, however. On a red dwarf planet, photosynthesis on the night side would be impossible, since it would never see the sun. On the day side, because the sun does not rise or set, areas in the shadows of mountains would

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explosion of the massive star in the central part of the system. This supernova will disperse heavier elements throughout its vicinity, created during the phase when the massive star has moved off of the main sequence, and the systems of the potential low-mass stars (which are still on the main

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The role of Jupiter in the early history of the Solar System is somewhat better established, and the source of significantly less debate. Early in the Solar System's history, Jupiter is accepted as having played an important role in the hydration of our planet: it increased the eccentricity of

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Habitability is also influenced by the architecture of the planetary system around a star. The evolution and stability of these systems are determined by gravitational dynamics, which drive the orbital evolution of terrestrial planets. Data collected on the orbital eccentricities of extrasolar

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should be present in or relatively close to the HZ, thus disrupting the formation of Earth-size bodies. The matter in the asteroid belt, for example, appears to have been unable to accrete into a planet due to orbital resonances with Jupiter; if the giant had appeared in the region that is now

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proceed exceptionally slowly, and they emit very little light (from 3% of that produced by the Sun to as little as 0.01%). Any planet in orbit around a red dwarf would have to huddle very close to its parent star to attain Earth-like surface temperatures; from 0.3 AU (just inside the orbit of

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is the difference between a planet's farthest and closest approach to its parent star divided by the sum of said distances. It is a ratio describing the shape of the elliptical orbit. The greater the eccentricity the greater the temperature fluctuation on a planet's surface. Although they are

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The discovery of life in extreme conditions has complicated definitions of habitability, but also generated much excitement amongst researchers in greatly broadening the known range of conditions under which life can persist. For example, a planet that might otherwise be unable to support an

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seas on its surface. Organic-chemical reactions that only require minimum energy are possible in these seas, but whether any living system can be based on such minimal reactions is unclear, and would seem unlikely. These satellites are exceptions, but they prove that mass, as a criterion for

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and low-mass stars (~0.1–0.3 solar masses). However the very short lifespans of stars of more than a few solar masses would scarcely allow time for a planet to cool, let alone the time needed for a stable biosphere to develop. Massive stars are thus eliminated as possible abodes for life.

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in moderating the Earth's climate by stabilising the axial tilt. It has been suggested that a chaotic tilt may be a "deal-breaker" in terms of habitability—i.e. a satellite the size of the Moon is not only helpful but required to produce stability. This position remains controversial.

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where immense star densities are inimical to life, given excessive radiation and gravitational disturbance. Globular clusters are also primarily composed of older, probably metal-poor, stars. Furthermore, in globular clusters, the great ages of the stars would mean a large amount of

2305:, another optimist with regards to extraterrestrial life, considered the possibility of organisms that are always airborne within the high atmosphere of Jupiter in a 1976 paper. Cohen and Stewart also envisioned life in both a solar environment and in the atmosphere of a gas giant. 1098: 1878:

stars could help determine how common life in the universe might be, as red dwarfs make up between 70 and 90% of all the stars in the galaxy. However, it is important to bear in mind that flare stars could greatly reduce the habitability of exoplanets by eroding their atmosphere.

2115:. In such worlds, not only is light not available as an energy source, but the organic material brought by meteorites (thought to have been necessary to start life in some scenarios) may not easily reach the liquid water. If a planet can only harbor life below its surface, the 1041:

The planet should rotate relatively quickly so that the day-night cycle is not overlong. If a day takes years, the temperature differential between the day and night side will be pronounced, and problems similar to those noted with extreme orbital eccentricity will come to the

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habitats include bodies which initially enjoy Earth-like conditions, but do not keep their ability to sustain liquid water on their surface due to stellar or geophysical conditions. Mars, and possibly Venus are examples of this class where complex life forms may not develop.

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It is evident from these absorption and output plots that only the red and blue ends of the visible part of the electromagnetic spectrum are used by plants in photosynthesis. The reflection and transmission of the middle of the spectrum gives the leaves their green visual

884:, but it is the largest, by diameter and mass, and the densest of all terrestrial bodies. It is large enough to retain an atmosphere through gravity alone and large enough that its molten core remains a heat engine, driving the diverse geology of the surface (the decay of 460:

A recent study suggests that cooler stars that emit more light in the infrared and near infrared may actually host warmer planets with less ice and incidence of snowball states. These wavelengths are absorbed by their planets' ice and greenhouse gases and remain warmer.

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such systems but it would almost certainly not reach a sophisticated level given these time-frames and the fact that increases in luminosity would occur quite rapidly. Life around "O" class stars is exceptionally unlikely, as they shine for less than ten million years.

1953:) need only be 100 millibars (0.10 atm), for the star's heat to be effectively carried to the night side. This is well within the levels required for photosynthesis, though water would still remain frozen on the dark side in some of their models. Martin Heath of 953:

The mass of a potentially habitable exoplanet is between 0.1 and 5.0 Earth masses. However it is possible for a habitable world to have a mass as low as 0.0268 Earth Masses. The radius of a potentially habitable exoplanet would range between 0.5 and 1.5 Earth radii.

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will tend to offset the increases in luminosity. Assumptions made about atmospheric conditions and geology thus have as great an impact on a putative HZ range as does stellar evolution: the proposed parameters of the Sun's HZ, for example, have fluctuated greatly.

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Additional geological characteristics may be essential or major factors in the habitability of natural celestial bodies – including some that may shape the body's heat and magnetic field. Some of these are unknown or not well understood and being investigated by

1813:(AU, the average Earth–Sun distance) to several hundred. In latter instances, the gravitational effects will be negligible on a planet orbiting an otherwise suitable star and habitability potential will not be disrupted unless the orbit is highly eccentric (see 1034:

tilt, but also its variation over time must be considered. The Earth's tilt varies between 21.5 and 24.5 degrees over 41,000 years. A more drastic variation, or a much shorter periodicity, would induce climatic effects such as variations in seasonal severity.

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argue that microbial life is probably widespread while complex life is very rare and perhaps even unique to Earth. Current knowledge of Earth's history partly buttresses this theory: multi-celled organisms are believed to have emerged at the time of the

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are likely examples of this class. Their oceans are thought to be enclosed between thick ice layers. In such conditions, the emergence of even simple life forms may be very difficult because the necessary ingredients for life will likely be completely

713:. The possibility that life could evolve in the cloud tops of giant planets has not been decisively ruled out, though it is considered unlikely, as they have no surface and their gravity is enormous. The natural satellites of giant planets, meanwhile, 1908:, which would be locked to the planet instead of the star, allowing a more even distribution of radiation over the moon. It was long assumed that such a thick atmosphere would prevent sunlight from reaching the surface in the first place, preventing 1436:

The two current ecological approaches for predicting the potential habitability use 19 or 20 environmental factors, with emphasis on water availability, temperature, presence of nutrients, an energy source, and protection from solar ultraviolet and

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outgassing could not have accounted for the amount of water in Earth's oceans. The vast majority of the water—and arguably carbon—necessary for life must have come from the outer Solar System, away from the Sun's heat, where it could remain solid.

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for that reason: it provides a Mars analog and the moisture gradients along its edges are ideal for studying the boundary between sterility and habitability. The Atacama was the subject of study in 2003 that partly replicated experiments from the

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Europa must have big tides, so it's my favorite for microbial life," says Max Bernstein, an astrochemist and program scientist at NASA Headquarters in Washington, D.C. "Europa is considered by many as the best place to find life in the solar

293:. The classical habitable zone (HZ) is defined for surface conditions only; but a metabolism that does not depend on the stellar light can still exist outside the HZ, thriving in the interior of the planet where liquid water is available. 592:

of the mid-second millennium, for instance, may have been caused by a relatively long-term decline in the Sun's luminosity. Thus, a star does not have to be a true variable for differences in luminosity to affect habitability. Of known

946:, which otherwise would tend to strip away planetary atmosphere and to bombard living things with ionized particles. Mass is not the only criterion for producing a magnetic field—as the planet must also rotate fast enough to produce a 340:

environment can influence the evolution of planets and life, if it originated. Liquid water is a necessary but not sufficient condition for life as we know it, as habitability is a function of a multitude of environmental parameters.

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must be interpreted within a planetary and environmental context. Whether a planet will emerge as habitable depends on the sequence of events that led to its formation, which could include the production of organic molecules in

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has been studied as an astrobiological analog, with researchers suggesting rapid sediment infill created a protected microenvironment for microbial organisms; similar conditions may have occurred over the geological history of

1052:) should not be pronounced. In itself, precession need not affect habitability as it changes the direction of the tilt, not its degree. However, precession tends to accentuate variations caused by other orbital deviations; see 223:

of other planets and moons within the Solar System has provided critical information on defining habitability criteria and allowed for substantial geophysical comparisons between the Earth and other bodies. The discovery of

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down to a little less than 4,000 K (6,700 °C to 3,700 °C); the Sun, a G2 star at 5,777 K, is well within these bounds. This spectral range probably accounts for between 5% and 10% of stars in the local

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A supplement to the factors that support life's emergence is the notion that life itself, once formed, becomes a habitability factor in its own right. An important Earth example was the production of molecular oxygen gas

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close to 600 million years ago, but more than 3 billion years after life first appeared. That Earth life remained unicellular for so long underscores that the decisive step toward complex organisms need not necessarily

1784:-type stars could host habitable exoplanets. About half of the stars similar in temperature to the Sun could have a rocky planet able to support liquid water on its surface, according to research using data from NASA's 2301:: submicroscopic "nuclear molecules" combining to form creatures with a life cycle millions of times quicker than Earth life. Called "imaginative and tongue-in-cheek", the idea gave rise to science fiction depictions. 449:, in an orbit between these two planets. However, reviews of the discovery have placed the existence of this planet in doubt, and it is listed as "unconfirmed". In September 2012, the discovery of two planets orbiting 576:

do mitigate such effects, but their atmosphere might not be retained by planets orbiting variables, because the high-frequency energy buffeting these planets would continually strip them of their protective covering.

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Recent research suggests that very large stars, greater than ~100 solar masses, could have planetary systems consisting of hundreds of Mercury-sized planets within the habitable zone. Such systems could also contain

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Red dwarfs have one advantage over other stars as abodes for life: far greater longevity. It took 4.5 billion years before humanity appeared on Earth, and life as we know it will see suitable conditions for 1 to 2.3

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According to prevailing theory, the formation of the Moon commenced when a Mars-sized body struck the Earth in a glancing collision late in its formation, and the ejected material coalesced and fell into orbit (see

7392: 1076:, which in turn aids the dynamic churning of Earth's large liquid water oceans. These lunar forces not only help ensure that the oceans do not stagnate, but also play a critical role in Earth's dynamic climate. 1317:

impacting with the Earth in the Solar System's early years would have deposited vast amounts of water, along with the other volatile compounds life requires, onto the early Earth, providing a kick-start to the

601:; unfortunately for the prospects of life existing in its proximity, the only significant difference between the two bodies is the amplitude of the solar cycle, which appears to be much greater for 18 Scorpii. 3268: 4421: 1097: 2148:

Along with the characteristics of planets and their star systems, the wider galactic environment may also impact habitability. Scientists considered the possibility that particular areas of galaxies (

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more. Red dwarfs, by contrast, could live for trillions of years because their nuclear reactions are far slower than those of larger stars, meaning that life would have longer to evolve and survive.

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atmosphere given the solar conditions in its vicinity, might be able to do so within a deep shadowed rift or volcanic cave. Similarly, craterous terrain might offer a refuge for primitive life. The

228:, beginning in the early 1990s and accelerating thereafter, has provided further information for the study of possible extraterrestrial life. These findings confirm that the Sun is not unique among 10393: 361:) correlates to overall mass. The appropriate spectral range for habitable stars is considered to be "late F" or "G", to "mid-K". This corresponds to temperatures of a little more than 7,000 1206:. Carbon has an unparalleled ability to bond with itself and to form a massive array of intricate and varied structures, making it an ideal material for the complex mechanisms that form living 328:

However, what makes a planet habitable is a much more complex question than having a planet located at the right distance from its host star so that water can be liquid on its surface: various

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Schuerger, Andrew C.; Golden, D.C.; Ming, Doug W. (November 2012). "Biotoxicity of Mars soils: 1. Dry deposition of analog soils on microbial colonies and survival under Martian conditions".

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This article is an analysis of planetary habitability from the perspective of contemporary physical science. A historical viewpoint on the possibility of habitable planets can be found at

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However, the evidence is not quite so clear. Research has shown that Jupiter's role in determining the rate at which objects hit Earth is significantly more complicated than once thought.

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of stars could be used to identify those which are more likely to host habitable Earth-like planets. As of 2020, radionuclides are thought to be produced by rare stellar processes such as

564:: living things adapted to a specific temperature range could not survive too great a temperature variation. Further, upswings in luminosity are generally accompanied by massive doses of 2412:

include yet unknown factors influencing the thermal habitability of planets such as "feedback mechanism (or mechanisms) that prevents the climate ever wandering to fatal temperatures".

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Such a situation can be expected on water-rich planets located too far from their star to allow surface liquid water, but on which subsurface water is in liquid form because of the

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The circular orbit of the Sun around the galactic center keeps it out of the way of the galaxy's spiral arms where intense radiation and gravitation may again lead to disruption.

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In a review of the factors which are important for the evolution of habitable Earth-sized planets, Lammer et al. proposed a classification of four water-dependent habitat types:

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The HEC uses the following terms to classify exoplanets in terms of mass, from least to greatest: asteroidan, mercurian, subterran, terran, superterran, neptunian, and jovian.

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in 1975, argues that life as a whole fosters and maintains suitable conditions for itself by helping to create a planetary environment suitable for its continuity. Similarly,

725: 4697:; Nixon, Conor A.; Affholder, Antonin; Chatain, Audrey; Cockell, Charles; Farnsworth, Kendra K.; Higgins, Peter M.; Miller, Kelly E.; Soderlund, Krista M. (1 February 2024). 2744: 2230:

While most investigations of extraterrestrial life start with the assumption that advanced life-forms must have similar requirements for life as on Earth, the hypothesis of

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and other scientists have proposed a Planet Habitability Index whose criteria include "potential for holding a liquid solvent" that is not necessarily restricted to water.

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showcase that even old red dwarfs can have significant flare activity. Barnard's Star was long assumed to have little activity, but in 1998 astronomers observed an intense

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live, suggest that there may be many more habitable places in the Universe than considered possible until very recently. On 4 November 2013, astronomers reported, based on

5896:"Simulations of the Atmospheres of Synchronously Rotating Terrestrial Planets Orbiting M Dwarfs: Conditions for Atmospheric Collapse and the Implications for Habitability" 10383: 2613:

flourish in environments that were once considered hostile to life. The potential occurrence of complex multi-celled life remains much more controversial. In their work

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stars are also suitable hosts for habitable planets is perhaps the most important open question in the entire field of planetary habitability given their prevalence (

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habitats are planetary bodies on which stellar and geophysical conditions allow liquid water to be available at the surface, along with sunlight, so that complex

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main-sequence stars of the "O" classes and many members of the "B" classes usually live less than 500 million years and in exceptional cases less than 10 million.

1210:. Hydrogen and oxygen, in the form of water, compose the solvent in which biological processes take place and in which the first reactions occurred that led to 2650:, which are 13 and 17 Earth masses. This is probably just chance, as there is no geophysical barrier to the formation of intermediate bodies (see for instance 580:

The Sun, in this respect as in many others, is relatively benign: the variation between its maximum and minimum energy output is roughly 0.1% over its 11-year

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As with other criteria, stability is the critical consideration in evaluating the effect of orbital and rotational characteristics on planetary habitability.

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must be interpreted within a planetary and environmental context. In determining the habitability potential of a body, studies focus on its bulk composition,

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and planet formation also means that habitable systems are more likely to be found around stars of younger generations, since stars that formed early in the

3201: 904:(which is smaller than any of the terrestrial planets) is volcanically dynamic because of the gravitational stresses induced by its orbit, and its neighbor 849:

and thus higher surface-to-volume ratios than their larger cousins. Such bodies tend to lose the energy left over from their formation quickly and end up

483:-shaped region of space surrounding a star in which a planet could maintain liquid water on its surface. The concept was first proposed by astrophysicist 10437: 2378:, and eventually photosynthesizing plants, leading to a radical change in the composition of Earth's atmosphere. This environmental change is called the 5410:

Navarro-González, Rafael; McKay, Christopher P. (7 November 2003). "Mars-Like Soils in the Atacama Desert, Chile, and the Dry Limit of Microbial Life".

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may be very rare, but non-carbon-based complex life could possibly emerge in other environments. The most frequently mentioned alternative to carbon is

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would not likely modify the whole planetary environment in an observable way, thus, detecting its presence on an exoplanet would be extremely difficult.

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effect of such a heavy atmosphere would tend to suggest that the habitable zone should be further out from the central star for such massive planets.

869:. Plate tectonics appear particularly crucial, at least on Earth: not only does the process recycle important chemicals and minerals, it also fosters 10222: 10217: 8648: 8638: 7740: 7730: 5666: 4878: 3942: 512:

HZ and a correspondingly smaller chance of developing life. Calculating an HZ range and its long-term movement is never straightforward, as negative

5563: 2702: 893:", terrestrial planets with higher masses than Earth, would have higher levels of plate tectonics and thus be firmly placed in the habitable range. 10378: 9841: 8935: 7187: 3590: 3232: 560:

stars are considered poor candidates for hosting life-bearing planets, as their unpredictability and energy output changes would negatively impact

5370: 3771: 822:, with its thin atmosphere, is colder than the Earth would be if it were at a similar distance from the Sun), and provide less protection against 8347: 7058: 1974:, and on the Earth the process depends on visible light. There are potential positives to this scenario. Numerous terrestrial ecosystems rely on 1887:

Astronomers for many years ruled out red dwarfs as potential abodes for life. Their small size (from 0.08 to 0.45 solar masses) means that their

1218:

between carbon and oxygen, available by oxidizing organic compounds, is the fuel of all complex life-forms. These four elements together make up

290: 5284: 10145: 8940: 1874:

M-type stars also considered possible hosts of habitable exoplanets, even those with flares such as Proxima b. Determining the habitability of

5026: 4190: 3971: 441:

and may possess liquid water. However it is also possible that a greenhouse effect may render it too hot to support life, while its neighbor,

7285: 3612: 7356:

If The Universe Is Teeming With Aliens ... Where Is Everybody? Fifty Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life

6373: 5752: 4147: 4086: 2895:"Water worlds could support life, study says – Analysis by UChicago, Penn State scientists challenges idea that life requires 'Earth clone'" 10636: 7645: 2169:

by the host or other nearby stars, which due to their proximity may cause extreme harm to life on any planets, provided that they can form.

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Relative abundance in space does not always mirror differentiated abundance within planets; of the four life elements, for instance, only

10116: 9699: 9243: 7815: 5695: 991:

must also meet certain criteria if life is to have the opportunity to evolve. A first assumption is that the planet should have moderate

731:

In analyzing which environments are likely to support life, a distinction is usually made between simple, unicellular organisms such as

588:

that even minor changes in the Sun's luminosity have had significant effects on the Earth's climate well within the historical era: the

8558: 8070: 2095:

habitats are planetary bodies where liquid water oceans exist below the surface, where they can interact directly with a silicate-rich

141:

has defined the principal habitability criteria as "extended regions of liquid water, conditions favorable for the assembly of complex

6100: 1979:

of a day-night cycle, including the weak light of morning and evening, far more energy would be available at a given radiation level.

10432: 9976: 9384: 8257: 3444: 2452: 10152: 1116:

in rocky planet mantles may be critical for the habitability of Earth-like planets. Such planets with higher abundances likely lack

316:" (or Catalogue of Habitable Stellar Systems) in 2002. The catalogue was formed by winnowing the nearly 120,000 stars of the larger 10415: 10252: 9981: 8985: 8653: 7750: 7665: 5895: 3116:

Altermann, Wladyslaw (2008). "From Fossils to Astrobiology – A Roadmap to Fata Morgana?". In Seckbach, Joseph; Walsh, Maud (eds.).

2753: 2482: 1301:

showed that, with the application of energy, simple inorganic compounds exposed to a primordial atmosphere can react to synthesize

1045:

The planet also should rotate quickly enough so that a magnetic dynamo may be started in its iron core to produce a magnetic field.

1026:

seasonal variation. Scientists do not know whether this trend will continue indefinitely with further increases in axial tilt (see

297: 20: 6047: 3637:; Whittet, DC; Sheldon, WR (August 1997). "Ultraviolet radiation from F and K stars and implications for planetary habitability". 2609:

There is an emerging consensus that single-celled micro-organisms may in fact be common in the universe, especially since Earth's

10783: 9020: 8790: 8168: 5691: 1121: 10099: 1186:, are also the most common chemically reactive elements in the universe. Indeed, simple biogenic compounds, such as very simple 10585: 10128: 7501: 1411:, generally considered the driest place on Earth, appears unable to support life, and it has been subject to study by NASA and 5615: 5249: 2859: 1840:

is conservatively estimated at 1.2 to 1.3 AU and Centauri B at 0.73 to 0.74—well within the stable region in both cases.

873:

through continent creation and increased environmental complexity and helps create the convective cells necessary to generate

10560: 10512: 10507: 10502: 10497: 10492: 10487: 10482: 10477: 10472: 10467: 10462: 10457: 10452: 10447: 10442: 10133: 8691: 8158: 7363: 7274: 7225: 5860: 3470: 3150: 3125: 2179:

It is not near the galactic center where once again star densities increase the likelihood of ionizing radiation (e.g., from

830:. Further, where an atmosphere is less dense than 0.006 Earth atmospheres, water cannot exist in liquid form as the required 6451: 4035:

Williams, Darren M.; Kasting, James F.; Wade, Richard A. (January 1997). "Habitable moons around extrasolar giant planets".

2130:

If the water layer is thick enough, water at its base will be in solid phase (ice polymorphs) because of the high pressure.

1836:

deviating by less than 5% during 32 000 binary periods). The continuous habitable zone (CHZ for 4.5 billion years) for

1407:

support life are still instructive to astrobiologists in defining the limits of what organisms can endure. The heart of the

639:

formation. Any planets that did form around a metal-poor star would probably be low in mass, and thus unfavorable for life.

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on a planet or satellite endogenously or be transferred to it from another body, through a hypothetical process known as

9645: 3856: 10570: 10420: 10227: 10104: 9253: 9096: 8623: 8272: 7715: 7640: 6476:

Dirk Schulze-Makuch; et al. (December 2011). "A Two-Tiered Approach to Assessing the Habitability of Exoplanets".

2463: 2231: 2225: 1621: 714: 4578:"High-resolution simulations of the final assembly of Earth-like planets 2: water delivery and planetary habitability" 908:

may have a liquid ocean or icy slush underneath a frozen shell also due to power generated from orbiting a gas giant.

192:

are a primary focus of astrobiological research, although more speculative habitability theories occasionally examine

10603: 10237: 8633: 8252: 8173: 7725: 7349: 7335: 7315: 7301: 7250: 5868: 5721: 4452: 4158: 2469: 2337:. Thus, while the gas giants are now helpful protectors, they were once suppliers of critical habitability material. 1849: 976:

perfectly circular, with an eccentricity of less than 0.02; other planets in the Solar System (with the exception of

445:, may be a more likely candidate for habitability. In September 2010, the discovery was announced of another planet, 422: 370:. "Middle-class" stars of this sort have a number of characteristics considered important to planetary habitability: 6750:

Horner, Jonathan; Jones, B. W.; Chambers, J. (January 2010). "Jupiter – friend or foe? III: the Oort cloud comets".

3805: 3334: 537:, Earth would almost certainly not have developed in its present form. However a gas giant inside the HZ might have 281:

away, according to the scientists. As of June 2021, a total of 59 potentially habitable exoplanets have been found.

98:

which appear favorable to life's flourishing. Of particular interest are those factors that have sustained complex,

10741: 10629: 10298: 10288: 9776: 9190: 8785: 8277: 8110: 7630: 3876:"The Effect of Host Star Spectral Energy Distribution and Ice-Albedo Feedback on the Climate of Extrasolar Planets" 3085: 2536: 1749:

Mesoplanets would be ideal for complex life, whereas hypopsychroplanets and hyperthermoplanets might only support

685:, and the orbital location in the planetary system. The chief assumption about habitable planets is that they are 10997: 10373: 10324: 10247: 10086: 9389: 8215: 8090: 7745: 5589: 5051:

Nimmo, Francis; Primack, Joel; Faber, S. M.; Ramirez-Ruiz, Enrico; Safarzadeh, Mohammadtaher (10 November 2020).

3831: 6017: 1072:

In the case of the Earth, the sole Moon is sufficiently massive and orbits so as to significantly contribute to

842:), does not occur. In addition, a lessened pressure reduces the range of temperatures at which water is liquid. 10329: 8775: 8333: 8100: 8045: 7407: 6245:

Kashi, Amit; Soker, Noam (2011). "The outcome of the protoplanetary disk of very massive stars, January 2011".

4223:

Sagan, C.; Salpeter, E. E. (1976). "Particles, environments, and possible ecologies in the Jovian atmosphere".

3170: 2982:

Wolszczan, A.; Frail, D. A. (9 January 1992). "A planetary system around the millisecond pulsar PSR1257 + 12".

1982:

Red dwarfs are far more variable and violent than their more stable, larger cousins. Often they are covered in

967:

adaptive, living organisms can stand only so much variation, particularly if the fluctuations overlap both the

627:). A high proportion of metals in a star correlates to the amount of heavy material initially available in the 7006:

Porter, Simon B.; Grundy, William M. (July 2011), "Post-capture Evolution of Potentially Habitable Exomoons",

2348:) make it very difficult for an independent Earth-like planet to exist in the system. See the discussion of a 2211:"suburban" location, such as the Solar System enjoys, is preferable to a Galaxy's center or farthest reaches. 1166:

It is generally assumed that any extraterrestrial life that might exist will be based on the same fundamental

10761: 10555: 10202: 10157: 10036: 10026: 10021: 10006: 10001: 9040: 8908: 8717: 8608: 8313: 8148: 8008: 7820: 7700: 7080: 6589: 6395: 6216: 4900: 2457: 1987:

form biological precursors, but also because it would blow off sizeable portions of the planet's atmosphere.

10540: 9886: 1970:

as we understand it would be complicated by the fact that a red dwarf produces most of its radiation in the

918:, meanwhile, has an outside chance of harbouring life, as it has retained a thick atmosphere and has liquid 11017: 10192: 9971: 9228: 9101: 8598: 7690: 865:

which supply the surface with life-sustaining material and the atmosphere with temperature moderators like

208:

The idea that planets beyond Earth might host life is an ancient one, though historically it was framed by

9846: 5567: 1293:

of volatile compounds through the first volcanoes would have contributed to the formation of the planets'

277:. 11 billion of these estimated planets may be orbiting Sun-like stars. The nearest such planet may be 12 11007: 10736: 10622: 10535: 10334: 9086: 8810: 8282: 8267: 8183: 7860: 5782:

Wiegert, Paul A.; Holman, Matt J. (April 1997). "The stability of planets in the Alpha Centauri system".

5315: 5118: 4482: 4162: 3608: 2712: 2620: 2589: 2251: 1954: 1825:

has shown that gas giants can form around stars in binary systems much as they do around solitary stars.

1814: 457:, about 6.9 times the mass of Earth and somewhat hotter, was considered to be within the habitable zone. 9993: 7785: 5952: 5507:

Beaty, David W.; et al. (14 July 2006), the Mars Exploration Program Analysis Group (MEPAG) (ed.),

3118:

From Fossils to Astrobiology: Records of Life on Earth and the Search for Extraterrestrial Biosignatures

3025:

Wolszczan, A (1994). "Confirmation of Earth Mass Planets Orbiting the Millisecond Pulsar PSR:B1257+12".

10865: 10659: 10368: 10363: 10353: 10111: 9771: 9160: 8878: 8800: 8115: 7494: 6540: 5385: 5165: 4940:

Lasker, J.; Joutel, F.; Robutel, P. (July 1993). "Stabilization of the earth's obliquity by the moon".

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More speculative ideas have focused on bodies altogether different from Earth-like planets. Astronomer

1298: 764: 193: 7790: 2592:

evaluate plausible scenarios in which life might form in the cloud-tops of Jovian planets. Similarly,

1866:) would have to huddle close to achieve Earth-like temperatures, probably inducing tidal locking. See 106:

creatures. Research and theory in this regard is a component of a number of natural sciences, such as

10598: 10348: 10016: 9801: 9685: 8745: 8553: 8193: 8024: 7615: 7426: 5292: 4337: 2927: 2476: 1777: 1773: 1769: 1670: Climate and its variability (geography, seasons, diurnal, and eventually, obliquity variations) 1294: 1106: 874: 795: 573: 492: 407: 6277: 5590:"Does life exist outside of the solar system? | Center for Astrophysics | Harvard & Smithsonian" 4775: 2894: 10773: 10358: 10303: 10164: 10056: 9951: 9711: 9354: 8918: 8225: 6544: 6104: 4785: 4555: 4547: 4198: 4094: 4010: 3538: 2383: 682: 10071: 7094: 6073: 3604: 2340:

In contrast, Jupiter-sized bodies that orbit too close to the habitable zone but not in it (as in

1710:

The Habitable Exoplanets Catalog uses estimated surface temperature range to classify exoplanets:

399:

Liquid water may exist on the surface of planets orbiting them at a distance that does not induce

19:"Habitable planet" redirects here. For a list of potentially habitable planets found to date, see 11012: 10746: 10580: 10283: 10207: 9781: 9319: 8613: 8120: 7886: 7705: 5760: 5143: 4478: 4309: 4098: 3688: 2669: 2188: 2149: 1529: 1371:

are Earth organisms that live in niche environments under severe conditions generally considered

880:"Low mass" is partly a relative label: the Earth is low mass when compared to the Solar System's 810:

or stirred by collision. Planets without a thick atmosphere lack the matter necessary for primal

747:, which involves "hot, ocean-covered planets with hydrogen-rich atmospheres", has been reported. 2824:

Costanza, Robert; Bernard, C. Patten (December 1995). "Defining and predicting sustainability".

2062: 740:

life generally, but in every case multicellular organisms are more picky than unicellular life.

137:

criteria must be met before an astronomical body can support life. In its astrobiology roadmap,

10842: 10293: 9786: 9736: 9170: 9145: 9135: 8975: 8854: 7569: 6478: 6272: 6127:"Atmospheric pressure as a natural climate regulator for a terrestrial planet with a biosphere" 4301: 4279: 2585: 2271: 2244: 2079: 1785: 1380: 721: 350: 301: 248: 9761: 4986: 2466: – Measure of the potential of natural satellites to have environments hospitable to life 923:

habitability, cannot necessarily be considered definitive at this stage of our understanding.

11002: 10852: 10811: 10778: 10751: 10705: 10262: 10031: 9906: 9806: 9640: 9273: 9175: 9000: 8893: 8728: 8663: 8356: 8301: 8240: 8065: 7760: 7625: 7487: 4918: 2615: 2565: 2505: 2493: 2379: 2294: 2259: 1867: 1412: 382: 9831: 7454: 6644:

Horner, Jonathan; Jones, B. W. (October 2008). "Jupiter – Friend or Foe? I: The Asteroids".

6620: 5508: 5482: 4667: 3424: 3366: 1424:

could be recovered from two soil samples, and incubation experiments were also negative for

786:

atmosphere, is colder than the Earth would be if it were at a similar distance from the Sun.

10806: 10756: 10669: 10575: 10550: 10530: 10140: 9811: 9726: 9422: 9349: 9263: 9150: 9140: 9111: 8928: 8823: 8247: 8235: 8130: 8080: 8075: 7974: 7917: 7906: 7810: 7660: 7544: 7534: 7422: 7132: 7025: 6960: 6893: 6826: 6769: 6716: 6663: 6616: 6487: 6432: 6338: 6264: 6141: 5967: 5910: 5801: 5756: 5523: 5478: 5419: 5327: 5228: 5199: 5074: 4951: 4829: 4710: 4599: 4356: 4232: 4044: 3986: 3897: 3767: 3646: 3495: 3420: 3287: 3034: 2991: 2946: 2833: 2782: 2400: 1938:

in California have shown that a planet's atmosphere (assuming it included greenhouse gases

1935: 1930:

This pessimism has been tempered by research. Studies by Robert Haberle and Manoj Joshi of

1822: 963: 831: 6697:

Horner, Jonathan; Jones, B. W. (April 2009). "Jupiter – friend or foe? II: the Centaurs".

4752: 3568:

Of Aliens and Exoplanets: Why the search for life, probably, requires the search for water

2860:"Goal 1: Understand the nature and distribution of habitable environments in the Universe" 2234:

suggests the possibility of lifeforms evolving around a different metabolic mechanism. In

1006:

If a planet is radically tilted, seasons will be extreme and make it more difficult for a

232:

in hosting planets and expands the habitability research horizon beyond the Solar System.

8: 10939: 10715: 10664: 10343: 9891: 9871: 9826: 9796: 9605: 9600: 9399: 9076: 8923: 8903: 8849: 8815: 8710: 8382: 8370: 8230: 8055: 7464: 5316:"Impact Craters as biospheric microenvironments, Lawn Hill Structure, Northern Australia" 5169: 2651: 2642:

There is a "mass-gap" in the Solar System between Earth and the two smallest gas giants,

2508: – Hypothetical type of planet or moon that may be better-suited for life than Earth 2434: 2283: 1484: 1417: 1199: 1149: 1141: 1053: 678: 628: 317: 197: 10967: 7840: 7136: 7029: 6964: 6897: 6830: 6773: 6720: 6667: 6491: 6436: 6342: 6268: 6145: 6126: 5971: 5926: 5914: 5805: 5527: 5423: 5331: 5078: 4955: 4833: 4714: 4603: 4360: 4236: 4048: 3990: 3901: 3650: 3499: 3291: 3038: 2995: 2950: 2837: 2786: 1128:

which may often be necessary for life to develop or persist as they shield planets from

10927: 10915: 10710: 10679: 10645: 9939: 9856: 9816: 9731: 9431: 9312: 9198: 9055: 9005: 8795: 8723: 8060: 7158: 7041: 7015: 6924: 6881: 6857: 6816: 6804: 6785: 6759: 6732: 6706: 6679: 6653: 6423: 6354: 6328: 6290: 6254: 6164: 5991: 5817: 5791: 5451: 5435: 5351: 5119:"The existence of a magnetic field beyond 3.5 billion years ago is still up for debate" 5100: 5064: 4967: 4847: 4819: 4698: 4623: 4589: 4483:"New class of habitable exoplanets represent a big step forward in the search for life" 4372: 4346: 4068: 3918: 3887: 3875: 3722: 3670: 3584: 3511: 3485: 3436: 3310: 3277: 3263: 3237: 3206: 3175: 3066: 3050: 3007: 2964: 2936: 2806: 2629: 2624: 2580: 2499: 2267: 2236: 1634: 1611: 1384: 690: 686: 631:. A smaller amount of metal makes the formation of planets much less likely, under the 374:

They live at least a few hundred million years, allowing life a chance to evolve. More

258: 255: 217: 185: 75:. Environments do not need to contain life to be considered habitable nor are accepted 7037: 6231: 5699: 4641: 2496: – Hypothesis that complex extraterrestrial life is improbable and extremely rare 1372: 1367:, operate in micro-organisms that act on and respond to changing micro-environments." 660: 321:

to the formation and development of habitable planets than smaller galaxies, like the

10187: 9821: 9569: 9564: 9513: 9363: 8831: 8701: 8400: 8394: 8188: 7938: 7891: 7855: 7595: 7574: 7359: 7345: 7331: 7311: 7297: 7270: 7246: 7221: 7162: 7150: 7074: 7061:. Astrobiology Magazine. 22 September 2005. Archived from the original on 3 June 2011 7045: 6988: 6983: 6948: 6929: 6911: 6862: 6844: 6629: 6604: 6583: 6503: 6389: 6358: 6294: 6210: 6169: 5983: 5539: 5443: 5343: 5104: 5092: 4894: 4851: 4734: 4726: 4615: 4425: 4368: 4060: 4002: 3923: 3662: 3572: 3440: 3404:

Lammer, H.; Bredehöft, J. H.; Coustenis, A.; Khodachenko, M. L.; et al. (2009).

3339: 3315: 3146: 3121: 3058: 2845: 2810: 2798: 2166: 1992: 1810: 1696: 1676: Substrate (soil processes, rock microenvironments, dust composition, shielding) 1651: 1510: 1360: 305: 220: 177: 168:, and potential chemical interactions. Stellar characteristics of importance include 142: 111: 83: 56: 32:

Understanding planetary habitability is partly an extrapolation of the conditions on

8678: 5995: 5821: 5455: 5355: 4805: 4627: 4376: 3744: 3515: 3367:"The Habitable Exoplanets Catalog – Planetary Habitability Laboratory @ UPR Arecibo" 3070: 2968: 1729:- medium temperature (0–50 °C; not to be confused with the other definition of 10891: 10790: 10684: 10565: 10313: 10076: 10066: 9926: 9876: 9766: 9756: 9680: 9610: 9595: 9394: 9278: 9218: 9165: 9071: 9045: 8945: 8522: 8376: 7800: 7140: 7033: 6978: 6968: 6919: 6901: 6852: 6834: 6789: 6777: 6736: 6724: 6683: 6671: 6624: 6495: 6346: 6282: 6159: 6149: 5975: 5918: 5809: 5531: 5486: 5427: 5335: 5261: 5082: 4971: 4959: 4942: 4837: 4718: 4607: 4364: 4248: 4240: 4072: 4052: 3994: 3913: 3905: 3674: 3654: 3503: 3428: 3305: 3295: 3042: 3011: 2999: 2954: 2871: 2841: 2790: 2540: 2487: 2341: 2161: 2112: 1946: 1901: 1893: 1888: 1392: 1356: 1137: 1133: 1120:

for a significant fraction of their lifetimes, and those with lower concentrations

977: 943: 790:

Low-mass planets are poor candidates for life for two reasons. First, their lesser

636: 367: 337: 213: 7188:"Earth has stayed habitable for billions of years – exactly how lucky did we get?" 6197:. Astrobiology Magazine. 29 August 2005. Archived from the original on 3 June 2011 5951:

Heath, Martin J.; Doyle, Laurance R.; Joshi, Manoj M.; Haberle, Robert M. (1999).

5872: 4155:

Proceedings of 12th Cambridge Workshop on Cool Stars, Stellar Systems, and The Sun

3519: 2037:

However, a massive-star system could be a progenitor of life in another way – the

1532:(e.g. Zn, Ni, Cu, Cr, As, Cd, etc.; some are essential, but toxic at high levels) 1375:

to life. Usually (although not always) unicellular, extremophiles include acutely

1350:

and an ideal environment to study the boundary between sterility and habitability.

10766: 10011: 9851: 9751: 9675: 9665: 9444: 9293: 9283: 9106: 8965: 8950: 8913: 8898: 8844: 8770: 8463: 8095: 7928: 7554: 6286: 3046: 2395: 2387: 2135: 2131: 2104: 1833: 1564: 1270: 1254: 862: 839: 803: 760: 674: 585: 480: 235:

While Earth is the only place in the Universe known to harbor life, estimates of

4914: 2353:

close, circular orbit that is coplanar with the planet's orbit around the star.

2126:

habitats have liquid water layers between two ice layers, or liquids above ice.

1257:. This can be partly explained by the fact that many of these elements, such as 930:

Finally, a larger planet is likely to have a large iron core. This allows for a

216:. The late 20th century saw two breakthroughs in the field. The observation and 10951: 10879: 10720: 9916: 9911: 9716: 9625: 9180: 9081: 9010: 8960: 8836: 8734: 8471: 8014: 7610: 7549: 7524: 7173: 7145: 7120: 6307: 5087: 5053:"Radiogenic Heating and Its Influence on Rocky Planet Dynamos and Habitability" 5052: 4842: 4807: 4422:"Exclusive: "Most Earth-Like" Exoplanet Gets Major Demotion—It Isn't Habitable" 3269:

Proceedings of the National Academy of Sciences of the United States of America

3197: 2959: 2922: 2544: 2428: 2391: 2156:, on the Milky Way galaxy's edge is considered to be in a life-favorable spot: 2096: 1975: 1967: 1939: 1909: 1905: 1837: 1829: 1683: 1582: 1573: 1408: 1339: 1319: 1266: 1207: 1125: 1027: 968: 931: 866: 589: 538: 474: 434: 262: 236: 76: 28: 6781: 6728: 6675: 6350: 5979: 5667:"About Half of Sun-Like Stars Could Host Rocky, Potentially Habitable Planets" 5490: 4391:"NASA Finds Earth-size Planet Candidates in Habitable Zone, Six Planet System" 4278:. The Encyclopedia of Astrobiology, Astronomy, and Spaceflight. Archived from 3943:"About Half of Sun-Like Stars Could Host Rocky, Potentially Habitable Planets" 3658: 3576: 3432: 1383:

organisms and others that can survive water temperatures above 100 °C in

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objects, which can bring catastrophe if knocked into the inner Solar System.

2108: 1996: 1897: 1454: 1364: 1343: 1215: 1117: 972: 947: 935: 905: 870: 815: 748: 550: 400: 358: 243:

and new insights into the extreme habitats on Earth where organisms known as

134: 99: 87: 6949:"The occurrence of Jovian planets and the habitability of planetary systems" 6906: 6839: 6154: 5564:"PHL's Exoplanets Catalog - Planetary Habitability Laboratory @ UPR Arecibo" 5431: 4253: 3300: 3262:

Petigura, Eric A.; Howard, Andrew W.; Marcy, Geoffrey W. (31 October 2013).

2794: 1854: 1802:

Typical estimates often suggest that 50% or more of all stellar systems are

10903: 10832: 10689: 10197: 10182: 10061: 9958: 9881: 9650: 9630: 9620: 9518: 9454: 9288: 9233: 9213: 9208: 9203: 9155: 9030: 8970: 8603: 8568: 7695: 7650: 7635: 7620: 7605: 7564: 7559: 7539: 7529: 7510: 7410:

was created from a revision of this article dated 22 January 2006

6992: 6933: 6866: 6507: 6173: 6125:

Li, King-Fai; Pahlevan, Kaveh; Kirschvink, Joseph L.; Yung, Yuk L. (2009).

6048:"AstronomyCast episode 40: American Astronomical Society Meeting, May 2007" 5987: 5922: 5543: 5535: 5447: 5347: 5339: 5220: 5191: 4806:

Constantin W. Arnscheidt; Robin D. Wordsworth; Feng Ding (13 August 2019).

4780: 4738: 4694: 4619: 4510: 4006: 3998: 3927: 3871: 3666: 3319: 3062: 2802: 2610: 2514: 2440: 2344:), or have a highly elliptical orbit that crosses the habitable zone (like 2298: 2275: 2263: 2255: 2030: 1750: 1425: 1368: 1167: 1161: 1113: 939: 915: 811: 752: 744: 669: 640: 632: 594: 484: 454: 446: 442: 426: 266: 244: 189: 157: 150: 115: 95: 6973: 6499: 5729: 4722: 4456: 4064: 3909: 3471:"Target selection for SETI: A catalog of nearby habitable stellar systems" 3086:"NASA Technical Memorandum 102363 – Extraterrestrial Life in the Universe" 396:

They emit sufficient radiation at wavelengths conducive to photosynthesis.

10123: 9901: 9896: 9866: 9836: 9791: 9746: 9741: 9670: 9655: 9590: 9534: 9529: 9495: 9480: 9475: 9469: 9223: 8888: 8696: 8514: 8506: 8412: 7991: 7881: 7600: 7590: 7264: 6319:

Forget, François (July 2013). "On the probability of habitable planets".

5796: 5250:"Understand the evolutionary mechanisms and environmental limits of life" 4594: 3490: 3166: 2655: 2422: 2290: 2204: 1924: 1863: 1859: 1803: 1781: 1376: 1219: 1211: 1073: 1011: 890: 885: 783: 610: 581: 430: 354: 333: 309: 181: 130: 125:

source, and the notion of planetary habitability implies that many other

103: 68: 60: 8325: 7255:(2021-01-26) Kepler-22b, the Oceanic Exoplanet - "Finding a New Earth", 2191:

at the centers of galaxies may also prove a danger to any nearby bodies.

10094: 9861: 9635: 9559: 9485: 9464: 9238: 9116: 9035: 8479: 7968: 7655: 5439: 5144:"Organic Molecule, Amino Acid-Like, Found in Constellation Sagittarius" 3527:

Habitability criteria defined—the foundational source for this article.

3202:"As Ranks of Goldilocks Planets Grow, Astronomers Consider What's Next" 3054: 2899: 2593: 2302: 2200: 2184: 2000: 1923:, a potentially habitable planet orbiting a red dwarf constituent in a 1915: 1730: 1644: 1630: 1544: 1438: 1302: 1290: 1243: 1231: 1202:. These four elements together comprise over 96% of Earth's collective 1187: 1129: 1049: 1015: 996: 858: 807: 775: 694: 624: 598: 556: 450: 390: 375: 329: 278: 209: 173: 169: 165: 146: 126: 72: 10946: 6570:. Astrobiology Magazine. Archived from the original on 8 February 2012 3566: 2437: – 2007 European study concept of an array of space observatories 1809:

The separation between stars in a binary may range from less than one

623:, there is a significant variation in the amount of heavier elements ( 10614: 9544: 9539: 9505: 9490: 9379: 9258: 8995: 8990: 8805: 8780: 8487: 8105: 7962: 7923: 7901: 6805:"Jupiter's decisive role in the inner Solar System's early evolution" 5288: 4963: 4576:

Raymond, Sean N.; Quinn, Thomas; Lunine, Jonathan I. (January 2007).

4056: 3835: 3543: 3003: 2446: 2241: 2173: 2153: 2116: 2038: 1920: 1875: 1818: 1610: Low pressure (is there a low-pressure threshold for terrestrial 1309: 1195: 1007: 901: 881: 827: 823: 756: 710: 644: 565: 525: 517: 438: 418: 322: 274: 270: 240: 225: 107: 7121:"Chance played a role in determining whether Earth stayed habitable" 4699:"Organic Input to Titan's Subsurface Ocean Through Impact Cratering" 4577: 3723:"The violent youth of solar proxies steer course of genesis of life" 10874: 9934: 8980: 8955: 8867: 8860: 8755: 8686: 8163: 8153: 8085: 7876: 7850: 7825: 7435:

Planetary Sciences and Habitability Group, Spanish Research Council

6821: 5813: 5069: 4881:. Astrobiology Magazine. Archived from the original on 19 June 2021 4824: 4514: 4487: 4244: 3507: 3403: 2941: 2345: 2180: 2067: 1983: 1971: 1503: C, H, N, O, P, S, essential metals, essential micronutrients 1476: 1262: 1258: 1183: 1175: 1000: 988: 846: 799: 732: 702: 698: 649: 616: 561: 513: 7020: 6764: 6711: 6658: 6376:. Astrobiology Magazine. Archived from the original on 3 June 2011 6333: 6259: 5835: 5640: 5027:"Stellar Smashups May Fuel Planetary Habitability, Study Suggests" 4351: 3892: 3282: 2152:) are better suited to life than others; the Solar System, in the 1065: 950:

within its core—but it is a significant component of the process.

9946: 8765: 8740: 8444: 8019: 7845: 5950: 4668:"Titan Most Likely Non-Habitable, Astrobiologists Say | Sci.News" 2647: 2597: 2333:

the gravitational scattering of Jupiter and, to a lesser extent,

2314: 1286: 1278: 1274: 1223: 1203: 1191: 1019: 919: 897: 854: 850: 791: 736: 6195:"M Dwarfs: The Search for Life is On, Interview with Todd Henry" 10847: 10257: 9585: 9409: 9344: 9248: 8760: 8668: 8262: 7835: 7805: 7795: 7755: 7479: 3869: 3747:(Press release). Astronomy & Astrophysics. 13 December 2007 3565:

Giovanni, Modirrousta-Galian, Darius Maddalena (4 April 2021).

2643: 2334: 1282: 1265:, along with their simplest and most common compounds, such as 1250: 1227: 1179: 1171: 1084: 992: 911: 706: 620: 362: 313: 122: 52: 37: 7434: 6547:. The Encyclopedia of Astrobiology, Astronomy, and Spaceflight 5894:

Joshi, M. M.; Haberle, R. M.; Reynolds, R. T. (October 1997).

5865:

NASA Specialized Center of Research and Training in Exobiology

5172:. The Encyclopedia of Astrobiology, Astronomy, and Spaceflight 4148:"Confirming the Metal-Rich Nature of Stars with Giant Planets" 3874:; Pierrehumbert, R. T.; Joshi, M. M.; Robinson, T. D. (2013). 2502: – Concept of permanent human habitation outside of Earth 1018:) than it has been in the past, coinciding with reduced polar 9304: 8178: 8050: 7168: 6101:"'The end of the world' has already begun, UW scientists say" 5509:"Findings of the Mars Special Regions Science Analysis Group" 5050: 1314: 1170:

as found on Earth, as the four elements most vital for life,

569: 530: 386: 239:

around other stars, along with the discovery of thousands of

161: 33: 7474: 4471: 4306:

Millennium Mathematics Project, Videoconferences for Schools

3539:"Giant Galaxies May Be Better Cradles for Habitable Planets" 2543:. For a discussion of the probability of alien life see the 1862:. Any planet around a red dwarf such as the one shown here ( 664:

The moons of some gas giants could potentially be habitable.

10837: 8530: 8125: 7439: 7283:

Fogg, Martyn J., ed. "Terraforming" (entire special issue)

7112: 5381: 5257: 4394: 3093: 2867: 2707: 1931: 1397: 1347: 1061: 835: 819: 779: 534: 289:

An understanding of planetary habitability begins with the

229: 138: 64: 41: 10898: 7469: 7095:"Chance played a major role in keeping Earth fit for life" 6223: 4693:

Neish, Catherine; Malaska, Michael J.; Sotin, Christophe;

4146:

Santos, Nuno C.; Israelian, Garik; Mayor, Michael (2003).

3264:"Prevalence of Earth-size planets orbiting Sun-like stars" 2431: – Orbits where planets may have liquid surface water 1334: 10546:

Exoplanetary Circumstellar Environments and Disk Explorer

8221:

Astrobiology Science and Technology for Exploring Planets

1421: 1289:

and oxygen, accounting for oxygen's relative abundance).

1239: 1235: 701:

rocks, and have not accreted the gaseous outer layers of

597:, one that closely resembles the Sun is considered to be 411: 91: 7243:

Evolving the Alien: The Science of Extraterrestrial Life

7218:

Rare Earth: Why Complex Life is Uncommon in the Universe

6124: 2616:

Rare Earth: Why Complex Life Is Uncommon in the Universe

2472: – Possible factors for life around red dwarf stars 2313:"Good Jupiters" are gas giants, like the Solar System's 743:

In August 2021, a new class of habitable planets, named

7444: 4755:. Science & Environment. BBC News. 23 November 2011 4511:"Alien life could be living on big 'Hycean' exoplanets" 4477: 4333: 3966: 3798:"A Hot Potential Habitable Exoplanet around Gliese 163" 2510:

Pages displaying short descriptions of redirect targets

2390:, a scientific model of the geo-biosphere pioneered by 1480: 1226:, the substance of living tissue. In addition, neither 6020:(www.kencroswell.com/reddwarflife.html Full reprint). 5671:

Exoplanet Exploration: Planets Beyond our Solar System

4692: 3947:

Exoplanet Exploration: Planets Beyond our Solar System

2551:. Habitable planets are also a staple of fiction; see 2460: – Liquid water naturally occurring outside Earth 2262:, is restrictive and unimaginative. They suggest that 1960: 1329: 1056:. Precession on Earth occurs over a 26,000-year cycle. 896:

Exceptional circumstances do offer exceptional cases:

90:

of conditions on Earth and the characteristics of the

10863: 9269:

Potential cultural impact of extraterrestrial contact

5409: 3633: 3469:

Turnbull, Margaret C.; Tarter, Jill C. (March 2003).

3140: 7322:

Lonely Planets: The Natural Philosophy of Alien Life

6882:"Jupiter's role in sculpting the early Solar System" 6803:

Batygin, Konstantin; Laughlin, Greg (7 April 2015).

5893: 4453:"Cosmic census finds crowd of planets in our galaxy" 4145: 3832:"Newfound Alien Planet a Top Contender to Host Life" 2738: 2736: 2734: 2732: 2730: 1014:. The axial tilt of the Earth is higher now (in the 999:(or obliquity) relative to the perpendicular of the 6749: 6475: 5468: 4939: 4034: 3804:(Planetary Habitability Laboratory). Archived from 3335:"Milky Way may host billions of Earth-size planets" 3261: 1214:. The energy released in the formation of powerful 681:, delivery of materials during and after planetary 16:

Known extent to which a planet is suitable for life

4808:"Atmospheric Evolution on Low-gravity Waterworlds" 4575: 3745:"Gliese 581: one planet might indeed be habitable" 2517: – Hypothetical planetary engineering process 2443: – Planet with environment similar to Earth's 385:to trigger important atmospheric dynamics such as 10223:Habitability of K-type main-sequence star systems 10218:Habitability of F-type main-sequence star systems 8649:Habitability of F-type main-sequence star systems 8639:Habitability of K-type main-sequence star systems 7741:Habitability of F-type main-sequence star systems 7731:Habitability of K-type main-sequence star systems 6603:Horner, Jonathan; Jones, Barrie (December 2010). 4987:"Without the Moon, Would There Be Life on Earth?" 4218: 4216: 3825: 3823: 3721:Guinan, Edward; Cuntz, Manfred (10 August 2009). 3109: 2727: 980:) have eccentricities that are similarly benign. 465:within 10 parsecs (32.6 light years) of the Sun. 86:is unknown, planetary habitability is largely an 10989: 9842:List of interstellar and circumstellar molecules 8936:Communication with extraterrestrial intelligence 7294:Terraforming: Engineering Planetary Environments 5953:"Habitability of Planets Around Red Dwarf Stars" 5753:"Planetary Systems can from around Binary Stars" 5616:"We Live in the Rarest Type of Planetary System" 4302:"Could there be life in the outer solar system?" 3970:; Whitmore, Daniel P.; Reynolds, Ray T. (1993). 3326: 3257: 3255: 2921:Kite, Edwin S.; Ford, Eric B. (31 August 2018). 2356: 2068:Four classes of habitable planets based on water 767:(JWST), which was launched on 25 December 2021. 410:may be able to support life far longer than the 254:data, that there could be as many as 40 billion 7666:Search for extraterrestrial intelligence (SETI) 6953:Proceedings of the National Academy of Sciences 6886:Proceedings of the National Academy of Sciences 6809:Proceedings of the National Academy of Sciences 6802: 6521:Drake, Frank (1973). "Life on a Neutron Star". 6134:Proceedings of the National Academy of Sciences 5665:Center, By Frank Tavares NASA's Ames Research. 5371:"Too Dry for Life: The Atacama Desert and Mars" 3941:Center, By Frank Tavares NASA's Ames Research. 3857:"Planets May Keep Warmer in a Cool Star System" 3791: 3789: 3759: 3233:"Far-Off Planets Like the Earth Dot the Galaxy" 3226: 3224: 3190: 2823: 2773:Seager, Sara (2013). "Exoplanet Habitability". 2703:"The Solar System and Beyond is Awash in Water" 2696: 2694: 1643: Solar UV-induced volatile oxidants, e.g. 491:The inner edge of the HZ is the distance where 188:-type planets and moons with the potential for 79:(HZ) the only areas in which life might arise. 6118: 5960:Origins of Life and Evolution of the Biosphere 5313: 4213: 3849: 3820: 3468: 3399: 3397: 3395: 3393: 3391: 3389: 3387: 3361: 3359: 3357: 2981: 2701:Dyches, Preston; Chou, Felcia (7 April 2015). 2490: – Hypothesis for lack of detected aliens 1604: Extreme diurnal temperature fluctuations 1469: Past or future liquid (ice) inventories 1048:Change in the direction of the axis rotation ( 10630: 9320: 8341: 7495: 7286:Journal of the British Interplanetary Society 6098: 5781: 5285:"Cave Dwellers: ET Might Lurk in Dark Places" 4915:"Planetary Tilt Not A Spoiler For Habitation" 4222: 3772:Centre de données astronomiques de Strasbourg 3252: 2768: 2766: 2219: 1705: 1699:, ground water flow, surface water, glacial) 149:". In August 2018, researchers reported that 7646:List of microorganisms tested in outer space 7005: 6421:Dorminey, Bruce (July 2005). "Dark Threat". 6312: 5192:"How did chemistry and oceans produce this?" 4502: 3972:"Habitable Zones Around Main Sequence Stars" 3786: 3589:: CS1 maint: multiple names: authors list ( 3221: 3159: 2691: 2349: 2308: 2143: 1242:, and the adenosine phosphates essential to 1230:(required for the building of proteins) nor 655: 336:aspects, the radiation, and the host star's 9244:History of the extraterrestrial life debate 8941:Gauss's Pythagorean right triangle proposal 6696: 6643: 6602: 5696:Harvard-Smithsonian Center for Astrophysics 4646:Harvard-Smithsonian Center for Astrophysics 4444: 4225:The Astrophysical Journal Supplement Series 4185: 4183: 3720: 3639:Origins of Life and Evolution of Biospheres 3530: 3478:The Astrophysical Journal Supplement Series 3384: 3354: 2914: 2425: – Study of plants grown in spacecraft 2293:, a well-known proponent of the search for 2063:Red giant § Prospects for habitability 2056: 1900:, to as little as 0.032 AU for a star like 1759: 1538: Globally distributed oxidizing soils 1253:is present in any abundance in the Earth's 1222:, which in turn are the building blocks of 10637: 10623: 9327: 9313: 8559:Planetary habitability in the Solar System 8348: 8334: 8071:Enceladus Life Signatures and Habitability 7502: 7488: 6449: 6244: 5750: 5462: 5221:"How did the Earth Get to Look Like This?" 4450: 4329: 4327: 4266: 4264: 2763: 2700: 2107:. Two examples of such an environment are 1105:A visualization showing a simple model of 615:While the bulk of material in any star is 584:. There is strong (though not undisputed) 284: 9385:Exoplanet orbital and physical parameters 8355: 8258:European Astrobiology Network Association 7340:Schmidt, Stanley and Robert Zubrin, eds. 7306:Gonzalez, Guillermo and Richards, Jay W. 7144: 7019: 6982: 6972: 6923: 6905: 6856: 6838: 6820: 6763: 6710: 6657: 6628: 6332: 6276: 6258: 6163: 6153: 5836:"Habitable Exoplanet Observatory (HabEx)" 5795: 5641:"Habitable Exoplanet Observatory (HabEx)" 5086: 5068: 4841: 4823: 4593: 4350: 4252: 3917: 3891: 3489: 3309: 3299: 3281: 3115: 3077: 3024: 2958: 2940: 2886: 2006: 726:list of 1235 extrasolar planet candidates 102:organisms on Earth and not just simpler, 10253:List of potentially habitable exoplanets 8986:Search for extraterrestrial intelligence 8654:List of potentially habitable exoplanets 7751:List of potentially habitable exoplanets 7418:, and does not reflect subsequent edits. 7401: 6420: 6071: 6015: 5613: 5502: 5500: 4984: 4180: 3564: 3120:. Vol. 12. Springer. p. xvii. 2920: 2483:List of potentially habitable exoplanets 2382:. This oxygen proved fundamental to the 1914: 1853: 1689:concentrations in the global atmosphere 1333: 1091: 1083: 774: 715:remain valid candidates for hosting life 659: 544: 468: 63:and maintain environments hospitable to 27: 21:List of potentially habitable exoplanets 8791:Living Interplanetary Flight Experiment 8169:Living Interplanetary Flight Experiment 7358:New York: January 2002 Springer-Verlag 7185: 7118: 6947:Lunine, Jonathan I. (30 January 2001). 6565: 6041: 4876: 4324: 4261: 4191:"An interview with Dr. Darren Williams" 3830:Redd, Nola Taylor (20 September 2012). 3462: 3230: 3196: 3141:Horneck, Gerda; Petra Rettberg (2007). 2923:"Habitability of Exoplanet Waterworlds" 2449: – Planet outside the Solar System 2214: 845:Secondly, smaller planets have smaller 121:An absolute requirement for life is an 10990: 10644: 7216:Ward, Peter; Brownlee, Donald (2000). 7125:Communications Earth & Environment 6946: 6452:"Which alien worlds are most livable?" 6371: 6318: 4642:"Earth: A Borderline Planet for Life?" 3795: 3165: 3083: 2772: 2399:will co-evolve." This is the basis of 1037:Other orbital considerations include: 806:and be lost to space when buffeted by 10965: 10618: 10561:Geodynamics of terrestrial exoplanets 9308: 8692:Biological Oxidant and Life Detection 8329: 8159:Biological Oxidant and Life Detection 7483: 6752:International Journal of Astrobiology 6699:International Journal of Astrobiology 6646:International Journal of Astrobiology 6520: 6321:International Journal of Astrobiology 6065: 5506: 5497: 5368: 4508: 4451:Borenstein, Seth (19 February 2011). 4419: 4413: 3774:(Strasbourg astronomical Data Center) 3765: 3689:"Light Absorption for Photosynthesis" 3413:The Astronomy and Astrophysics Review 2892: 2406: 1431: 957: 722:Kepler Space Observatory Mission team 524:Second, no large-mass body such as a 488:HZ may have to be greatly expanded. 10243:Habitability of yellow dwarf systems 10233:Habitability of neutron star systems 8644:Habitability of yellow dwarf systems 8629:Habitability of neutron star systems 8389:Viking lander biological experiments 8308: 7736:Habitability of yellow dwarf systems 7721:Habitability of neutron star systems 7262: 6879: 6605:"Jupiter – Friend or Foe? An answer" 6566:Bortman, Henry (29 September 2004). 6229: 5282: 3829: 3802:University of Puerto Rico at Arecibo 3536: 3332: 2852: 2742: 2052:Habitability of neutron star systems 1843: 818:across their surfaces (for example, 572:radiation which might prove lethal. 10586:Sudarsky's gas giant classification 10213:Habitability of binary star systems 8619:Habitability of binary star systems 8594:Catalog of Nearby Habitable Systems 7711:Habitability of binary star systems 6539: 5556: 5164: 4753:"Most liveable alien worlds ranked" 4270: 3768:"LHS 188 – High proper-motion Star" 3537:Choi, Charles Q. (21 August 2015). 3231:Overbye, Dennis (4 November 2013). 3084:Graham, Robert W. (February 1990). 1961:Other factors limiting habitability 1798:Habitability of binary star systems 1330:Microenvironments and extremophiles 689:. Such planets, roughly within one 652:'s history have low metal content. 604: 453:was announced. One of the planets, 433:", has been found orbiting in the " 417:Whether fainter late K and M class 13: 10571:Nexus for Exoplanet System Science 10228:Habitability of natural satellites 9254:Nexus for Exoplanet System Science 9097:Hypothetical types of biochemistry 8624:Habitability of natural satellites 8273:Nexus for Exoplanet System Science 7716:Habitability of natural satellites 7641:Hypothetical types of biochemistry 7388: 7329:Gaia: A New Look at Life on Earth. 7269:(1st ed.). Rand Corporation. 7235: 7119:Tyrrell, Toby (11 December 2020). 5664: 4455:. Associated Press. Archived from 3940: 3725:. International Astronomical Union 2464:Habitability of natural satellites 2226:Hypothetical types of biochemistry 1622:ultraviolet germicidal irradiation 1420:landings on Mars in the 1970s; no 1124:. Planetary dynamos create strong 814:, have little insulation and poor 14: 11029: 10966:Smith, Yvette (26 January 2021). 10238:Habitability of red dwarf systems 8634:Habitability of red dwarf systems 8253:Center for Life Detection Science 8174:Mars Astrobiology Explorer-Cacher 7726:Habitability of red dwarf systems 7445:Planetary Habitability Laboratory 7369: 7186:Tyrrell, Toby (19 January 2021). 7008:The Astrophysical Journal Letters 6099:Hines, Sandra (13 January 2003). 6016:Croswell, Ken (27 January 2001). 5869:University of Southern California 5698:. 30 January 2006. Archived from 5692:"Most Milky Way Stars Are Single" 4985:Dorminey, Bruce (29 April 2009). 4397:. 2 February 2011. Archived from 4195:Astrobiology: The Living Universe 4091:Department of Atmospheric Science 3615:from the original on 14 June 2008 2470:Habitability of red dwarf systems 1850:Habitability of red dwarf systems 1791: 1088:Geological cross section of Earth 798:retention difficult. Constituent 423:habitability of red dwarf systems 344: 10959: 10945: 10933: 10921: 10909: 10897: 10885: 10873: 10335:Stars with proto-planetary discs 10299:NASA Star and Exoplanet Database 10289:Extrasolar Planets Encyclopaedia 9777:Extraterrestrial sample curation 9408: 8786:Life Investigation For Enceladus 8307: 8296: 8295: 8278:Ocean Worlds Exploration Program 8111:Life Investigation For Enceladus 7631:Extraterrestrial sample curation 7509: 7455:The Habitable Exoplanets Catalog 7400: 7179: 7167: 7087: 7051: 6999: 6940: 6873: 6796: 6743: 6690: 6637: 6630:10.1111/j.1468-4004.2010.51616.x 6596: 6559: 6533: 6514: 6469: 6443: 6414: 6402: 6365: 6301: 6238: 6230:Cain, Fraser (4 February 2009). 6187: 6092: 5369:McKay, Christopher (June 2002). 5260:. September 2003. Archived from 5170:"Elements, biological abundance" 4773: 3870:Shields, A. L.; Meadows, V. S.; 3406:"What makes a planet habitable?" 2537:Beliefs in extraterrestrial life 2045: 2023: 1637:(long-term accumulated effects) 1552:(surface and near-surface only) 770: 389:formation, but not so much that 381:They emit enough high-frequency 145:, and energy sources to sustain 10248:Habitable zone for complex life 9686:Ultra-short period planet (USP) 9390:Methods of detecting exoplanets 8216:Astrobiology Society of Britain 8091:Explorer of Enceladus and Titan 7746:Habitable zone for complex life 7209: 6450:Alan Boyle (22 November 2011). 6072:Croswell, Ken (November 2005). 6035: 6009: 5944: 5887: 5853: 5828: 5775: 5744: 5714: 5684: 5658: 5633: 5607: 5582: 5403: 5362: 5314:Lindsay, J; Brasier, M (2006). 5307: 5276: 5242: 5225:The Electronic Universe Project 5213: 5196:The Electronic Universe Project 5184: 5158: 5136: 5111: 5044: 5024: 5018: 5009: 4978: 4933: 4907: 4877:Bortman, Henry (22 June 2005). 4870: 4858: 4799: 4767: 4745: 4686: 4672:Sci.News: Breaking Science News 4660: 4634: 4569: 4548:"The Heat History of the Earth" 4540: 4528: 4383: 4294: 4139: 4113: 4079: 4028: 3960: 3934: 3863: 3796:Méndez, Abel (29 August 2012). 3737: 3714: 3681: 3627: 3597: 3558: 3333:Khan, Amina (4 November 2013). 3171:"Are We Alone in the Universe?" 3143:Complete Course in Astrobiology 3134: 3018: 2661: 2636: 2603: 2572: 2558: 1521:Toxin abundances and lethality: 1463: Activity of liquid water 1155: 1122:may often be geologically inert 987:A planet's movement around its 508:(carbon dioxide) condensation. 114:and the emerging discipline of 10429:Discovered exoplanets by year 9334: 8776:Journey to Enceladus and Titan 8101:Journey to Enceladus and Titan 7059:"The Living Worlds Hypothesis" 6568:"Coming Soon: "Good" Jupiters" 6372:Mullen, Leslie (18 May 2001). 5283:Hart, Stephen (17 June 2003). 4420:Grant, Andrew (8 March 2011). 2975: 2817: 2529: 1: 10556:Extrasolar planets in fiction 10203:Extraterrestrial liquid water 8909:Berkeley SETI Research Center 8609:Extraterrestrial liquid water 8149:Astrobiology Field Laboratory 7701:Extraterrestrial liquid water 7470:General interest astrobiology 7241:Cohen, Jack and Ian Stewart. 6880:Naoz, Smadar (7 April 2015). 5728:. Sol Company. Archived from 5722:"Stars and Habitable Planets" 5614:Billings, Lee (1 June 2023). 4776:"Magnetic Field of the Earth" 3097:. Lewis Research Center, Ohio 2684: 2596:suggested that the clouds of 2458:Extraterrestrial liquid water 2386:of later animal species. The 2357:Life's impact on habitability 2282:to water. The astrobiologist 1723:- cold (<−50 to 0 °C) 1717:- very cold (<−50 °C) 1518: Availability/mineralogy 1355:evolutionary forces, such as 1234:(needed for the formation of 479:The habitable zone (HZ) is a 203: 10576:Planets in globular clusters 10193:Circumstellar habitable zone 9229:Extraterrestrials in fiction 9102:Interplanetary contamination 8599:Circumstellar habitable zone 8483:(unusual light fluctuations) 8475:(unusual light fluctuations) 8467:(unusual light fluctuations) 8283:Spanish Astrobiology Center‎ 7691:Circumstellar habitable zone 6287:10.1016/j.newast.2010.06.003 6074:"A Flare for Barnard's Star" 3047:10.1126/science.264.5158.538 2846:10.1016/0921-8009(95)00048-8 2677:moon has not been disproven. 697:, are primarily composed of 668:Habitability indicators and 541:under the right conditions. 198:types of astronomical bodies 156:Habitability indicators and 7: 10536:Exoplanet naming convention 9646:Planet/Brown dwarf boundary 9087:Extraterrestrial hypothesis 8268:NASA Astrobiology Institute 7296:, SAE International, 1995. 7038:10.1088/2041-8205/736/1/L14 5871:, San Diego. Archived from 5751:Boss, Alan (January 2006). 5471:Planetary and Space Science 3766:Staff (20 September 2012). 3609:California State University 2415: 2278:are sometimes suggested as 2232:other types of biochemistry 1955:Greenwich Community College 1870:. Credit: MPIA/V. Joergens. 995:. If there is little or no 10: 11034: 10660:Interplanetary spaceflight 9772:Extraterrestrial materials 9406: 8801:Mars sample-return mission 8116:Mars sample return mission 7465:David Darling encyclopedia 7440:The Habitable Zone Gallery 7146:10.1038/s43247-020-00057-8 6374:"Galactic Habitable Zones" 5861:"Habitable zones of stars" 4369:10.1088/0004-637X/736/1/19 3698:. Georgia State University 2893:Staff (1 September 2018). 2746:NASA Astrobiology Strategy 2553:Planets in science fiction 2223: 2220:Alternative biochemistries 2060: 2049: 1919:An artist's impression of 1847: 1795: 1706:Classification terminology 1159: 1152:, geochemists and others. 1079: 1022:, warmer temperatures and 765:James Webb Space Telescope 608: 548: 472: 194:alternative biochemistries 18: 10825: 10799: 10729: 10698: 10652: 10599:Discoveries of exoplanets 10594: 10523: 10312: 10271: 10173: 10085: 9992: 9925: 9802:Interplanetary dust cloud 9698: 9578: 9504: 9430: 9417: 9372: 9340: 9189: 9125: 9064: 9019: 8877: 8677: 8582: 8554:Earliest known life forms 8546: 8499: 8456: 8429: 8422: 8363: 8291: 8206: 8194:Terrestrial Planet Finder 8139: 8038: 8000: 7984: 7952: 7869: 7778: 7769: 7679: 7616:Earliest known life forms 7583: 7517: 7266:Habitable Planets for Man 7263:Dole, Stephen H. (1965). 7215: 7079:: CS1 maint: unfit URL ( 6782:10.1017/S1473550409990346 6729:10.1017/S1473550408004357 6676:10.1017/S1473550408004187 6588:: CS1 maint: unfit URL ( 6408: 6394:: CS1 maint: unfit URL ( 6351:10.1017/S1473550413000128 6215:: CS1 maint: unfit URL ( 5491:10.1016/j.pss.2012.07.026 5057:The Astrophysical Journal 4899:: CS1 maint: unfit URL ( 4864: 4812:The Astrophysical Journal 4534: 4338:The Astrophysical Journal 3859:. Redorbit. 19 July 2013. 3692:(Graphic with references) 3433:10.1007/s00159-009-0019-z 2928:The Astrophysical Journal 2477:Habitable Planets for Man 2172:It is not near an active 2144:The galactic neighborhood 1860:photospheric temperatures 1631:Galactic cosmic radiation 1448:Some habitability factors 1446: 1439:galactic cosmic radiation 802:are more likely to reach 656:Planetary characteristics 643:studies of systems where 493:runaway greenhouse effect 10304:Open Exoplanet Catalogue 10279:Nearby Habitable Systems 10165:Transit-timing variation 8919:Breakthrough Initiatives 8226:Breakthrough Initiatives 6609:Astronomy and Geophysics 6105:University of Washington 6080:. Kalmbach Publishing Co 5784:The Astronomical Journal 5088:10.3847/2041-8213/abc251 4843:10.3847/1538-4357/ab2bf2 4786:Georgia State University 4612:10.1089/ast.2006.06-0126 4584:(Submitted manuscript). 4556:James Madison University 4509:Staff (27 August 2021). 4095:University of Washington 2960:10.3847/1538-4357/aad6e0 2522: 2189:supermassive black holes 2150:galactic habitable zones 2057:Post-main sequence stars 1858:Relative star sizes and 1760:Alternative star systems 1403:Earth environments that 751:may soon be studied for 393:destroys incipient life. 355:photospheric temperature 353:of a star indicates its 10784:Trans-Neptunian objects 10581:Small planet radius gap 10284:Exoplanet Data Explorer 10208:Galactic habitable zone 9782:Giant-impact hypothesis 9023:extraterrestrial beings 8614:Galactic habitable zone 7887:Mars Science Laboratory 7706:Galactic habitable zone 6907:10.1073/pnas.1503865112 6840:10.1073/pnas.1423252112 6621:2010A&G....51f..16H 6545:"Neutron star, life on" 6155:10.1073/pnas.0809436106 6018:"Red, willing and able" 5980:10.1023/A:1006596718708 5483:2012P&SS...72...91S 5432:10.1126/science.1089143 4479:University of Cambridge 4310:University of Cambridge 3659:10.1023/A:1006596806012 3425:2009A&ARv..17..181L 3301:10.1073/pnas.1319909110 2795:10.1126/science.1232226 2670:giant impact hypothesis 2080:multicellular organisms 1999:, showing that it is a 1882: 285:Stellar characteristics 10998:Planetary habitability 10843:National Space Society 10675:Planetary habitability 10541:Exoplanet phase curves 10379:Terrestrial candidates 10330:Multiplanetary systems 10294:NASA Exoplanet Archive 9977:Mean-motion resonances 9787:Gravitational collapse 9737:Circumstellar envelope 9171:Planetarium hypothesis 9161:Hart–Tipler conjecture 9146:Dark forest hypothesis 9136:Aestivation hypothesis 8855:Venus In Situ Explorer 8659:Planetary habitability 8448:(misidentified quasar) 8440:(misidentified pulsar) 8066:Enceladus Life Finder‎ 8046:Breakthrough Enceladus 7570:Planetary oceanography 7396: 7376:Listen to this article 7324:, HarperCollins, 2004. 5923:10.1006/icar.1997.5793 5536:10.1089/ast.2006.6.677 5340:10.1089/ast.2006.6.348 4991:scientificamerican.com 4197:. 2000. Archived from 4159:University of Colorado 3999:10.1006/icar.1993.1010 2319:Comet Shoemaker–Levy 9 2007:Longevity and ubiquity 1927: 1871: 1786:Kepler Space Telescope 1739:- hot (50-100 °C) 1351: 1346:provides an analog to 1299:Miller–Urey experiment 1136:. The electromagnetic 1109: 1107:Earth's magnetic field 1089: 875:Earth's magnetic field 787: 757:terrestrial telescopes 665: 529:between the orbits of 296:Under the auspices of 49:Planetary habitability 45: 36:, as this is the only 10968:"Finding a New Earth" 10853:The Planetary Society 10416:Potentially habitable 10321:Exoplanetary systems 10263:Superhabitable planet 10022:F/Yellow-white dwarfs 9907:Sample-return mission 9807:Interplanetary medium 9274:Post-detection policy 9176:Rare Earth hypothesis 9001:Voyager Golden Record 8894:Allen Telescope Array 8729:Enceladus Life Finder 8664:Superhabitable planet 8357:Extraterrestrial life 8241:Breakthrough Starshot 7841:Lunar Micro Ecosystem 7761:Superhabitable planet 7626:Extraterrestrial life 7395: 7308:The Privileged Planet 7245:, Ebury Press, 2002. 6974:10.1073/pnas.98.3.809 6500:10.1089/ast.2010.0592 5254:Astrobiology: Roadmap 4993:. Scientific American 4919:Penn State University 4723:10.1089/ast.2023.0055 3910:10.1089/ast.2012.0961 2864:Astrobiology: Roadmap 2743:NASA (October 2015), 2506:Superhabitable planet 2494:Rare Earth hypothesis 2380:Great Oxidation Event 2350:stable habitable zone 2297:, imagined life on a 2295:extraterrestrial life 2260:Rare Earth hypothesis 1918: 1857: 1635:solar particle events 1337: 1194:, have been found in 1160:Further information: 1104: 1087: 778: 720:In February 2011 the 663: 545:Low stellar variation 469:Stable habitable zone 383:ultraviolet radiation 31: 10800:Terraforming targets 10730:Colonization targets 10670:Intergalactic travel 10551:Extragalactic planet 10531:Carl Sagan Institute 9812:Interplanetary space 9727:Circumplanetary disk 9400:Planet-hosting stars 9264:Planetary protection 9151:Firstborn hypothesis 9141:Berserker hypothesis 9112:Mediocrity principle 8929:Breakthrough Message 8547:Life in the Universe 8248:Carl Sagan Institute 8236:Breakthrough Message 8076:Enceladus Orbilander 7811:Biosatellite program 7661:Planetary protection 7545:Evolutionary biology 7535:Atmospheric sciences 7427:More spoken articles 5757:Carnegie Institution 5378:Ames Research Center 5229:University of Oregon 5200:University of Oregon 5146:. ScienceDaily. 2008 5015:File:Tidalwaves1.gif 4087:"The Little Ice Age" 3525:on 22 February 2006. 3169:(18 November 2013). 2826:Ecological Economics 2401:Earth system science 2321:impacted the giant. 2280:alternative solvents 2215:Other considerations 1936:Ames Research Center 1823:Carnegie Institution 1768:It is believed that 1745:- (> 100 °C) 1492:Chemical environment 1150:planetary scientists 1142:neutron star mergers 964:Orbital eccentricity 832:atmospheric pressure 679:protoplanetary disks 190:Earth-like chemistry 153:could support life. 82:As the existence of 51:is the measure of a 11018:Prebiotic chemistry 10665:Interstellar travel 9892:Protoplanetary disk 9872:Planetary migration 9827:Interstellar medium 9606:Circumtriple planet 9601:Circumbinary planet 9077:Directed panspermia 9056:Reptilian humanoids 8924:Breakthrough Listen 8904:Arecibo Observatory 8850:Titan Mare Explorer 8423:Signals of interest 8383:Murchison meteorite 8371:Shergotty meteorite 8231:Breakthrough Listen 7137:2020ComEE...1...61T 7030:2011ApJ...736L..14P 6965:2001PNAS...98..809L 6898:2015PNAS..112.4189N 6831:2015PNAS..112.4214B 6774:2010IJAsB...9....1H 6721:2009IJAsB...8...75H 6668:2008IJAsB...7..251H 6492:2011AsBio..11.1041S 6437:2005Ast....33g..40D 6343:2013IJAsB..12..177F 6269:2011NewA...16...27K 6146:2009PNAS..106.9576L 5972:1999OLEB...29..405H 5915:1997Icar..129..450J 5875:on 21 November 2000 5806:1997AJ....113.1445W 5620:Scientific American 5594:www.cfa.harvard.edu 5528:2006AsBio...6..677M 5424:2003Sci...302.1018N 5418:(5647): 1018–1021. 5332:2006AsBio...6..348L 5079:2020ApJ...903L..37N 5031:Scientific American 4956:1993Natur.361..615L 4834:2019ApJ...881...60A 4715:2024AsBio..24..177N 4604:2007AsBio...7...66R 4361:2011ApJ...736...19B 4282:on 10 February 2012 4237:1976ApJS...32..737S 4049:1996DPS....28.1221W 3991:1993Icar..101..108K 3902:2013AsBio..13..715S 3651:1997OLEB...27..413K 3500:2003ApJS..145..181T 3292:2013PNAS..11019273P 3276:(48): 19273–19278. 3039:1994Sci...264..538W 2996:1992Natur.355..145W 2951:2018ApJ...864...75K 2838:1995EcoEc..15..193C 2787:2013Sci...340..577S 2759:on 18 November 2016 2652:OGLE-2005-BLG-390Lb 2435:Darwin (spacecraft) 2284:Dirk Schulze-Makuch 1966:remain so forever. 1925:trinary star system 1591:physical conditions 1487:of available water 1200:interstellar medium 1118:a persistent dynamo 1054:Milankovitch cycles 826:and high-frequency 629:protoplanetary disk 359:main-sequence stars 318:Hipparcos Catalogue 11008:Space colonization 10711:McKendree cylinder 10680:Space and survival 10646:Space colonization 9857:Nebular hypothesis 9832:Interstellar space 9817:Interstellar cloud 9797:Internal structure 9732:Circumstellar disc 9199:Ancient astronauts 8796:Mars Geyser Hopper 8724:Enceladus Explorer 8364:Events and objects 8061:Enceladus Explorer 7397: 7342:Islands in the Sky 7320:Grinspoon, David. 6078:Astronomy Magazine 5264:on 26 January 2011 4695:Lopes, Rosaly M.C. 4674:. 20 February 2024 4481:(25 August 2021). 4459:on 15 January 2024 4276:"Jupiter, life on" 4101:on 9 February 2012 3808:on 21 October 2019 3238:The New York Times 3207:The New York Times 3200:(6 January 2015). 3176:The New York Times 2874:on 17 January 2011 2630:Cambrian explosion 2581:Evolving the Alien 2500:Space colonization 2407:The role of chance 2268:silicon-based life 2264:Earth-like planets 2237:Evolving the Alien 1928: 1896:) for a star like 1872: 1743:hyperthermoplanets 1715:hypopsychroplanets 1432:Ecological factors 1385:hydrothermal vents 1352: 1112:Concentrations of 1110: 1090: 1064:appears to play a 958:Orbit and rotation 853:dead, lacking the 788: 691:order of magnitude 666: 218:robotic spacecraft 69:generated directly 46: 10861: 10860: 10612: 10611: 10188:Astrooceanography 9822:Interstellar dust 9694: 9693: 9570:Ultra-hot Neptune 9565:Ultra-hot Jupiter 9514:Eccentric Jupiter 9364:Planetary science 9302: 9301: 8832:SpaceX Red Dragon 8747:Rosalind Franklin 8542: 8541: 8401:Allan Hills 84001 8395:Allan Hills 77005 8323: 8322: 8202: 8201: 8026:Rosalind Franklin 7939:Trace Gas Orbiter 7596:Allan Hills 84001 7575:Planetary science 7393: 7364:978-0-387-95501-8 7327:Lovelock, James. 7310:, Regnery, 2004. 7276:978-0-444-00092-7 7227:978-0-387-98701-9 6892:(14): 4189–4190. 6815:(14): 4214–4217. 6486:(10): 1041–1052. 6234:. Universe Today. 6232:"Red Dwarf Stars" 6140:(24): 9576–9579. 6103:(Press release). 5932:on 14 August 2011 5755:(Press release). 5702:on 13 August 2007 5694:(Press release). 5391:on 26 August 2009 4950:(6413): 615–617. 4917:(Press release). 4426:Discover Magazine 4201:on 28 August 2007 4043:(6613): 234–236. 3968:Kasting, James F. 3635:Kasting, James F. 3340:Los Angeles Times 3152:978-3-527-40660-9 3127:978-1-4020-8836-0 2990:(6356): 145–147. 2167:stellar evolution 1889:nuclear reactions 1844:Red dwarf systems 1811:astronomical unit 1703: 1702: 1598: Temperature 1102: 863:tectonic activity 306:Margaret Turnbull 143:organic molecules 112:planetary science 84:life beyond Earth 57:natural satellite 40:known to support 11025: 10983: 10982: 10980: 10978: 10963: 10950: 10949: 10938: 10937: 10936: 10926: 10925: 10924: 10914: 10913: 10912: 10902: 10901: 10890: 10889: 10888: 10878: 10877: 10869: 10716:O'Neill cylinder 10685:Space settlement 10639: 10632: 10625: 10616: 10615: 10566:Neptunian desert 9952:Tidally detached 9887:Planet formation 9877:Planetary system 9767:Exozodiacal dust 9757:Disrupted planet 9681:Ultra-cool dwarf 9611:Disrupted planet 9596:Chthonian planet 9428: 9427: 9412: 9395:Planetary system 9329: 9322: 9315: 9306: 9305: 9279:San Marino Scale 9219:Brookings Report 9166:Neocatastrophism 9072:Cosmic pluralism 9046:Little green men 9021:Types of alleged 8946:Astrolinguistics 8535: 8527: 8526:(unknown origin) 8523:Fast radio burst 8519: 8511: 8492: 8491:(unknown origin) 8488:HD 164595 signal 8484: 8476: 8468: 8449: 8441: 8427: 8426: 8377:Nakhla meteorite 8350: 8343: 8336: 8327: 8326: 8311: 8310: 8299: 8298: 7776: 7775: 7671:Yamato meteorite 7504: 7497: 7490: 7481: 7480: 7417: 7415: 7404: 7403: 7394: 7384: 7382: 7377: 7292:Fogg, Martyn J. 7280: 7231: 7203: 7202: 7200: 7198: 7192:The Conversation 7183: 7177: 7172:Available under 7171: 7166: 7148: 7116: 7110: 7109: 7107: 7105: 7091: 7085: 7084: 7078: 7070: 7068: 7066: 7055: 7049: 7048: 7023: 7003: 6997: 6996: 6986: 6976: 6944: 6938: 6937: 6927: 6909: 6877: 6871: 6870: 6860: 6842: 6824: 6800: 6794: 6793: 6767: 6747: 6741: 6740: 6714: 6694: 6688: 6687: 6661: 6652:(3–4): 251–261. 6641: 6635: 6634: 6632: 6600: 6594: 6593: 6587: 6579: 6577: 6575: 6563: 6557: 6556: 6554: 6552: 6537: 6531: 6530: 6518: 6512: 6511: 6473: 6467: 6466: 6464: 6462: 6447: 6441: 6440: 6418: 6412: 6406: 6400: 6399: 6393: 6385: 6383: 6381: 6369: 6363: 6362: 6336: 6316: 6310: 6308:Stellar mass#Age 6305: 6299: 6298: 6280: 6262: 6242: 6236: 6235: 6227: 6221: 6220: 6214: 6206: 6204: 6202: 6191: 6185: 6184: 6182: 6180: 6167: 6157: 6131: 6122: 6116: 6115: 6113: 6111: 6096: 6090: 6089: 6087: 6085: 6069: 6063: 6062: 6060: 6058: 6039: 6033: 6032: 6030: 6028: 6013: 6007: 6006: 6004: 6002: 5957: 5948: 5942: 5941: 5939: 5937: 5931: 5925:. Archived from 5900: 5891: 5885: 5884: 5882: 5880: 5857: 5851: 5850: 5848: 5846: 5840:www.jpl.nasa.gov 5832: 5826: 5825: 5799: 5797:astro-ph/9609106 5790:(4): 1445–1450. 5779: 5773: 5772: 5770: 5768: 5759:. Archived from 5748: 5742: 5741: 5739: 5737: 5718: 5712: 5711: 5709: 5707: 5688: 5682: 5681: 5679: 5677: 5662: 5656: 5655: 5653: 5651: 5645:www.jpl.nasa.gov 5637: 5631: 5630: 5628: 5626: 5611: 5605: 5604: 5602: 5600: 5586: 5580: 5579: 5577: 5575: 5566:. Archived from 5560: 5554: 5553: 5552: 5550: 5513: 5504: 5495: 5494: 5466: 5460: 5459: 5407: 5401: 5400: 5398: 5396: 5390: 5384:. Archived from 5375: 5366: 5360: 5359: 5311: 5305: 5304: 5302: 5300: 5291:. Archived from 5280: 5274: 5273: 5271: 5269: 5246: 5240: 5239: 5237: 5235: 5217: 5211: 5210: 5208: 5206: 5188: 5182: 5181: 5179: 5177: 5162: 5156: 5155: 5153: 5151: 5140: 5134: 5133: 5131: 5129: 5115: 5109: 5108: 5090: 5072: 5048: 5042: 5041: 5039: 5037: 5022: 5016: 5013: 5007: 5006: 5000: 4998: 4982: 4976: 4975: 4964:10.1038/361615a0 4937: 4931: 4930: 4928: 4926: 4921:. 25 August 2003 4911: 4905: 4904: 4898: 4890: 4888: 4886: 4879:"Elusive Earths" 4874: 4868: 4862: 4856: 4855: 4845: 4827: 4803: 4797: 4796: 4794: 4792: 4771: 4765: 4764: 4762: 4760: 4749: 4743: 4742: 4690: 4684: 4683: 4681: 4679: 4664: 4658: 4657: 4655: 4653: 4638: 4632: 4631: 4597: 4595:astro-ph/0510285 4573: 4567: 4566: 4564: 4562: 4544: 4538: 4532: 4526: 4525: 4523: 4521: 4506: 4500: 4499: 4497: 4495: 4475: 4469: 4468: 4466: 4464: 4448: 4442: 4441: 4439: 4437: 4432:on 15 March 2014 4428:. Archived from 4417: 4411: 4410: 4408: 4406: 4401:on 29 April 2011 4387: 4381: 4380: 4354: 4331: 4322: 4321: 4319: 4317: 4298: 4292: 4291: 4289: 4287: 4268: 4259: 4258: 4256: 4254:2060/19760019038 4220: 4211: 4210: 4208: 4206: 4187: 4178: 4177: 4175: 4173: 4168:on 15 April 2012 4167: 4161:. Archived from 4152: 4143: 4137: 4136: 4134: 4132: 4117: 4111: 4110: 4108: 4106: 4097:. Archived from 4083: 4077: 4076: 4057:10.1038/385234a0 4032: 4026: 4025: 4023: 4021: 4016:on 18 March 2009 4015: 4009:. Archived from 3976: 3964: 3958: 3957: 3955: 3953: 3938: 3932: 3931: 3921: 3895: 3867: 3861: 3860: 3853: 3847: 3846: 3844: 3842: 3827: 3818: 3817: 3815: 3813: 3793: 3784: 3783: 3781: 3779: 3763: 3757: 3756: 3754: 3752: 3741: 3735: 3734: 3732: 3730: 3718: 3712: 3711: 3705: 3703: 3696:phy-astr.gus.edu 3693: 3685: 3679: 3678: 3631: 3625: 3624: 3622: 3620: 3601: 3595: 3594: 3588: 3580: 3562: 3556: 3555: 3553: 3551: 3534: 3528: 3526: 3524: 3518:. Archived from 3493: 3491:astro-ph/0210675 3475: 3466: 3460: 3459: 3457: 3455: 3449: 3443:. Archived from 3410: 3401: 3382: 3381: 3379: 3377: 3363: 3352: 3351: 3349: 3347: 3330: 3324: 3323: 3313: 3303: 3285: 3259: 3250: 3249: 3247: 3245: 3228: 3219: 3218: 3216: 3214: 3194: 3188: 3187: 3185: 3183: 3163: 3157: 3156: 3138: 3132: 3131: 3113: 3107: 3106: 3104: 3102: 3090: 3081: 3075: 3074: 3033:(5158): 538–42. 3022: 3016: 3015: 3004:10.1038/355145a0 2979: 2973: 2972: 2962: 2944: 2918: 2912: 2911: 2909: 2907: 2890: 2884: 2883: 2881: 2879: 2870:. Archived from 2856: 2850: 2849: 2821: 2815: 2814: 2781:(577): 577–581. 2770: 2761: 2760: 2758: 2752:, archived from 2751: 2740: 2725: 2724: 2722: 2720: 2715:on 10 April 2015 2711:. Archived from 2698: 2678: 2665: 2659: 2640: 2634: 2607: 2601: 2600:might host life. 2576: 2570: 2564:Life appears to 2562: 2556: 2541:Cosmic pluralism 2533: 2511: 2488:Neocatastrophism 2373: 2372: 2371: 2342:47 Ursae Majoris 2162:globular cluster 2015: 1902:Proxima Centauri 1695: Transport ( 1444: 1443: 1393:Lawn Hill crater 1212:life's emergence 1138:emission spectra 1134:cosmic radiation 1103: 944:cosmic radiation 938:the planet from 761:space telescopes 675:molecular clouds 637:planetary system 605:High metallicity 507: 506: 505: 368:Milky Way galaxy 261:orbiting in the 214:physical science 59:'s potential to 11033: 11032: 11028: 11027: 11026: 11024: 11023: 11022: 10988: 10987: 10986: 10976: 10974: 10964: 10960: 10956: 10944: 10934: 10932: 10922: 10920: 10910: 10908: 10896: 10886: 10884: 10872: 10864: 10862: 10857: 10821: 10795: 10737:Lagrange points 10725: 10694: 10648: 10643: 10613: 10608: 10604:Search projects 10590: 10519: 10308: 10267: 10169: 10141:Radial velocity 10081: 10037:K/Orange dwarfs 10027:G/Yellow dwarfs 9988: 9982:Titius–Bode law 9921: 9852:Molecular cloud 9752:Detached object 9703: 9701: 9690: 9676:Toroidal planet 9666:Sub-brown dwarf 9574: 9500: 9472:(Super-Mercury) 9445:Coreless planet 9421: 9419: 9413: 9404: 9368: 9336: 9333: 9303: 9298: 9294:Xenoarchaeology 9284:Technosignature 9185: 9121: 9107:Kardashev scale 9060: 9022: 9015: 9011:Xenolinguistics 8976:Project Phoenix 8966:Project Cyclops 8951:Lincos language 8914:Bracewell probe 8899:Arecibo message 8880: 8873: 8771:Icebreaker Life 8673: 8585: 8578: 8538: 8533: 8525: 8517: 8509: 8495: 8490: 8482: 8474: 8466: 8452: 8447: 8439: 8418: 8359: 8354: 8324: 8319: 8287: 8208: 8198: 8141: 8135: 8096:Icebreaker Life 8034: 7996: 7980: 7954: 7948: 7865: 7771: 7765: 7682: 7675: 7579: 7555:Geomicrobiology 7513: 7508: 7431: 7430: 7419: 7413: 7411: 7408:This audio file 7405: 7398: 7389: 7386: 7380: 7379: 7375: 7372: 7344:, Wiley, 1996. 7277: 7238: 7236:Further reading 7228: 7212: 7207: 7206: 7196: 7194: 7184: 7180: 7117: 7113: 7103: 7101: 7093: 7092: 7088: 7072: 7071: 7064: 7062: 7057: 7056: 7052: 7004: 7000: 6945: 6941: 6878: 6874: 6801: 6797: 6748: 6744: 6695: 6691: 6642: 6638: 6601: 6597: 6581: 6580: 6573: 6571: 6564: 6560: 6550: 6548: 6538: 6534: 6519: 6515: 6474: 6470: 6460: 6458: 6448: 6444: 6419: 6415: 6407: 6403: 6387: 6386: 6379: 6377: 6370: 6366: 6317: 6313: 6306: 6302: 6278:10.1.1.770.1250 6243: 6239: 6228: 6224: 6208: 6207: 6200: 6198: 6193: 6192: 6188: 6178: 6176: 6129: 6123: 6119: 6109: 6107: 6097: 6093: 6083: 6081: 6070: 6066: 6056: 6054: 6040: 6036: 6026: 6024: 6014: 6010: 6000: 5998: 5955: 5949: 5945: 5935: 5933: 5929: 5898: 5892: 5888: 5878: 5876: 5859: 5858: 5854: 5844: 5842: 5834: 5833: 5829: 5780: 5776: 5766: 5764: 5749: 5745: 5735: 5733: 5732:on 28 June 2011 5720: 5719: 5715: 5705: 5703: 5690: 5689: 5685: 5675: 5673: 5663: 5659: 5649: 5647: 5639: 5638: 5634: 5624: 5622: 5612: 5608: 5598: 5596: 5588: 5587: 5583: 5573: 5571: 5562: 5561: 5557: 5548: 5546: 5511: 5505: 5498: 5467: 5463: 5408: 5404: 5394: 5392: 5388: 5373: 5367: 5363: 5312: 5308: 5298: 5296: 5295:on 20 June 2003 5281: 5277: 5267: 5265: 5248: 5247: 5243: 5233: 5231: 5219: 5218: 5214: 5204: 5202: 5190: 5189: 5185: 5175: 5173: 5163: 5159: 5149: 5147: 5142: 5141: 5137: 5127: 5125: 5117: 5116: 5112: 5049: 5045: 5035: 5033: 5023: 5019: 5014: 5010: 4996: 4994: 4983: 4979: 4938: 4934: 4924: 4922: 4913: 4912: 4908: 4892: 4891: 4884: 4882: 4875: 4871: 4863: 4859: 4804: 4800: 4790: 4788: 4772: 4768: 4758: 4756: 4751: 4750: 4746: 4691: 4687: 4677: 4675: 4666: 4665: 4661: 4651: 4649: 4640: 4639: 4635: 4574: 4570: 4560: 4558: 4546: 4545: 4541: 4533: 4529: 4519: 4517: 4507: 4503: 4493: 4491: 4476: 4472: 4462: 4460: 4449: 4445: 4435: 4433: 4418: 4414: 4404: 4402: 4389: 4388: 4384: 4332: 4325: 4315: 4313: 4300: 4299: 4295: 4285: 4283: 4269: 4262: 4221: 4214: 4204: 4202: 4189: 4188: 4181: 4171: 4169: 4165: 4150: 4144: 4140: 4130: 4128: 4119: 4118: 4114: 4104: 4102: 4085: 4084: 4080: 4033: 4029: 4019: 4017: 4013: 3974: 3965: 3961: 3951: 3949: 3939: 3935: 3868: 3864: 3855: 3854: 3850: 3840: 3838: 3828: 3821: 3811: 3809: 3794: 3787: 3777: 3775: 3764: 3760: 3750: 3748: 3743: 3742: 3738: 3728: 3726: 3719: 3715: 3701: 3699: 3691: 3687: 3686: 3682: 3632: 3628: 3618: 3616: 3611:, Los Angeles. 3603: 3602: 3598: 3582: 3581: 3563: 3559: 3549: 3547: 3535: 3531: 3522: 3473: 3467: 3463: 3453: 3451: 3447: 3408: 3402: 3385: 3375: 3373: 3365: 3364: 3355: 3345: 3343: 3331: 3327: 3260: 3253: 3243: 3241: 3229: 3222: 3212: 3210: 3198:Overbye, Dennis 3195: 3191: 3181: 3179: 3164: 3160: 3153: 3139: 3135: 3128: 3114: 3110: 3100: 3098: 3088: 3082: 3078: 3023: 3019: 2980: 2976: 2919: 2915: 2905: 2903: 2891: 2887: 2877: 2875: 2858: 2857: 2853: 2822: 2818: 2771: 2764: 2756: 2749: 2741: 2728: 2718: 2716: 2699: 2692: 2687: 2682: 2681: 2666: 2662: 2641: 2637: 2625:Donald Brownlee 2608: 2604: 2577: 2573: 2563: 2559: 2534: 2530: 2525: 2520: 2509: 2418: 2409: 2396:David Grinspoon 2388:Gaia hypothesis 2370: 2367: 2366: 2365: 2363: 2359: 2311: 2309:"Good Jupiters" 2258:, based on the 2228: 2222: 2217: 2160:It is not in a 2146: 2105:geothermal heat 2082:may originate. 2070: 2065: 2059: 2054: 2048: 2026: 2013: 2009: 1963: 1950: 1943: 1885: 1852: 1846: 1834:semi-major axis 1800: 1794: 1762: 1708: 1690: 1687: 1677: 1671: 1665: 1664: 1659: 1655: 1648: 1638: 1624: 1615: 1605: 1599: 1590: 1583:Redox gradients 1576: 1567: 1558: 1553: 1533: 1523: 1519: 1513: 1504: 1498: 1470: 1464: 1434: 1332: 1285:(a compound of 1271:carbon monoxide 1164: 1158: 1126:magnetic fields 1092: 1082: 989:rotational axis 960: 838:(608 Pa) (0.18 804:escape velocity 773: 658: 613: 607: 553: 547: 539:habitable moons 504: 501: 500: 499: 497: 477: 471: 347: 312:developed the " 302:Project Phoenix 287: 263:habitable zones 237:habitable zones 206: 77:habitable zones 24: 17: 12: 11: 5: 11031: 11021: 11020: 11015: 11013:Exoplanetology 11010: 11005: 11000: 10985: 10984: 10957: 10955: 10954: 10942: 10930: 10918: 10906: 10894: 10882: 10859: 10858: 10856: 10855: 10850: 10845: 10840: 10835: 10829: 10827: 10823: 10822: 10820: 10819: 10814: 10809: 10803: 10801: 10797: 10796: 10794: 10793: 10788: 10787: 10786: 10781: 10776: 10771: 10770: 10769: 10759: 10754: 10749: 10739: 10733: 10731: 10727: 10726: 10724: 10723: 10721:Stanford torus 10718: 10713: 10708: 10702: 10700: 10699:Space habitats 10696: 10695: 10693: 10692: 10687: 10682: 10677: 10672: 10667: 10662: 10656: 10654: 10650: 10649: 10642: 10641: 10634: 10627: 10619: 10610: 10609: 10607: 10606: 10601: 10595: 10592: 10591: 10589: 10588: 10583: 10578: 10573: 10568: 10563: 10558: 10553: 10548: 10543: 10538: 10533: 10527: 10525: 10521: 10520: 10518: 10517: 10516: 10515: 10510: 10505: 10500: 10495: 10490: 10485: 10480: 10475: 10470: 10465: 10460: 10455: 10450: 10445: 10440: 10435: 10426: 10425: 10424: 10423: 10418: 10413: 10408: 10407: 10406: 10401: 10396: 10391: 10381: 10376: 10371: 10366: 10361: 10356: 10351: 10340: 10339: 10338: 10337: 10332: 10327: 10318: 10316: 10310: 10309: 10307: 10306: 10301: 10296: 10291: 10286: 10281: 10275: 10273: 10269: 10268: 10266: 10265: 10260: 10255: 10250: 10245: 10240: 10235: 10230: 10225: 10220: 10215: 10210: 10205: 10200: 10195: 10190: 10185: 10179: 10177: 10171: 10170: 10168: 10167: 10162: 10161: 10160: 10153:Transit method 10150: 10149: 10148: 10138: 10137: 10136: 10126: 10121: 10120: 10119: 10109: 10108: 10107: 10100:Direct imaging 10097: 10091: 10089: 10083: 10082: 10080: 10079: 10074: 10069: 10064: 10059: 10054: 10049: 10044: 10039: 10034: 10029: 10024: 10019: 10014: 10009: 10004: 9998: 9996: 9990: 9989: 9987: 9986: 9985: 9984: 9979: 9974: 9969: 9961: 9956: 9955: 9954: 9944: 9943: 9942: 9931: 9929: 9923: 9922: 9920: 9919: 9917:Star formation 9914: 9912:Scattered disc 9909: 9904: 9899: 9894: 9889: 9884: 9879: 9874: 9869: 9864: 9859: 9854: 9849: 9844: 9839: 9834: 9829: 9824: 9819: 9814: 9809: 9804: 9799: 9794: 9789: 9784: 9779: 9774: 9769: 9764: 9762:Excretion disk 9759: 9754: 9749: 9744: 9739: 9734: 9729: 9724: 9719: 9717:Accretion disk 9714: 9708: 9706: 9696: 9695: 9692: 9691: 9689: 9688: 9683: 9678: 9673: 9668: 9663: 9658: 9653: 9648: 9643: 9638: 9633: 9628: 9626:Eyeball planet 9623: 9618: 9613: 9608: 9603: 9598: 9593: 9588: 9582: 9580: 9576: 9575: 9573: 9572: 9567: 9562: 9557: 9552: 9547: 9542: 9537: 9532: 9527: 9522: 9516: 9510: 9508: 9502: 9501: 9499: 9498: 9493: 9488: 9483: 9478: 9473: 9467: 9462: 9457: 9452: 9447: 9442: 9436: 9434: 9425: 9415: 9414: 9407: 9405: 9403: 9402: 9397: 9392: 9387: 9382: 9376: 9374: 9370: 9369: 9367: 9366: 9361: 9360: 9359: 9358: 9357: 9341: 9338: 9337: 9332: 9331: 9324: 9317: 9309: 9300: 9299: 9297: 9296: 9291: 9286: 9281: 9276: 9271: 9266: 9261: 9256: 9251: 9246: 9241: 9236: 9231: 9226: 9221: 9216: 9211: 9206: 9201: 9195: 9193: 9191:Related topics 9187: 9186: 9184: 9183: 9181:Zoo hypothesis 9178: 9173: 9168: 9163: 9158: 9153: 9148: 9143: 9138: 9132: 9130: 9123: 9122: 9120: 9119: 9114: 9109: 9104: 9099: 9094: 9089: 9084: 9082:Drake equation 9079: 9074: 9068: 9066: 9062: 9061: 9059: 9058: 9053: 9048: 9043: 9038: 9033: 9027: 9025: 9017: 9016: 9014: 9013: 9008: 9003: 8998: 8993: 8988: 8983: 8978: 8973: 8968: 8963: 8961:Pioneer plaque 8958: 8953: 8948: 8943: 8938: 8933: 8932: 8931: 8926: 8916: 8911: 8906: 8901: 8896: 8891: 8885: 8883: 8875: 8874: 8872: 8871: 8864: 8857: 8852: 8847: 8842: 8834: 8829: 8821: 8813: 8811:Northern Light 8808: 8803: 8798: 8793: 8788: 8783: 8778: 8773: 8768: 8763: 8758: 8753: 8752: 8751: 8738: 8735:Europa Clipper 8731: 8726: 8721: 8714: 8707: 8699: 8694: 8689: 8683: 8681: 8679:Space missions 8675: 8674: 8672: 8671: 8666: 8661: 8656: 8651: 8646: 8641: 8636: 8631: 8626: 8621: 8616: 8611: 8606: 8601: 8596: 8590: 8588: 8580: 8579: 8577: 8576: 8571: 8566: 8561: 8556: 8550: 8548: 8544: 8543: 8540: 8539: 8537: 8536: 8534:(radio signal) 8528: 8520: 8518:(inconclusive) 8512: 8510:(radio source) 8503: 8501: 8497: 8496: 8494: 8493: 8485: 8477: 8472:EPIC 204278916 8469: 8460: 8458: 8454: 8453: 8451: 8450: 8442: 8433: 8431: 8424: 8420: 8419: 8417: 8416: 8410: 8404: 8398: 8392: 8386: 8380: 8374: 8367: 8365: 8361: 8360: 8353: 8352: 8345: 8338: 8330: 8321: 8320: 8318: 8317: 8305: 8292: 8289: 8288: 8286: 8285: 8280: 8275: 8270: 8265: 8260: 8255: 8250: 8245: 8244: 8243: 8238: 8233: 8223: 8218: 8212: 8210: 8204: 8203: 8200: 8199: 8197: 8196: 8191: 8186: 8184:Northern Light 8181: 8176: 8171: 8166: 8161: 8156: 8151: 8145: 8143: 8140:Cancelled and 8137: 8136: 8134: 8133: 8128: 8123: 8118: 8113: 8108: 8103: 8098: 8093: 8088: 8083: 8078: 8073: 8068: 8063: 8058: 8053: 8048: 8042: 8040: 8036: 8035: 8033: 8032: 8031: 8030: 8017: 8015:Europa Clipper 8012: 8004: 8002: 7998: 7997: 7995: 7994: 7988: 7986: 7982: 7981: 7979: 7978: 7971: 7966: 7958: 7956: 7950: 7949: 7947: 7946: 7941: 7936: 7935: 7934: 7921: 7914: 7913: 7912: 7899: 7898: 7897: 7884: 7879: 7873: 7871: 7867: 7866: 7864: 7863: 7858: 7853: 7848: 7843: 7838: 7833: 7828: 7823: 7818: 7813: 7808: 7803: 7798: 7793: 7788: 7782: 7780: 7773: 7767: 7766: 7764: 7763: 7758: 7753: 7748: 7743: 7738: 7733: 7728: 7723: 7718: 7713: 7708: 7703: 7698: 7693: 7687: 7685: 7677: 7676: 7674: 7673: 7668: 7663: 7658: 7653: 7648: 7643: 7638: 7633: 7628: 7623: 7618: 7613: 7611:Drake equation 7608: 7603: 7598: 7593: 7587: 7585: 7581: 7580: 7578: 7577: 7572: 7567: 7562: 7557: 7552: 7550:Exoplanetology 7547: 7542: 7537: 7532: 7527: 7525:Astrochemistry 7521: 7519: 7515: 7514: 7507: 7506: 7499: 7492: 7484: 7478: 7477: 7472: 7467: 7462: 7452: 7442: 7437: 7420: 7406: 7399: 7387: 7374: 7373: 7371: 7370:External links 7368: 7367: 7366: 7354:Webb, Stephen 7352: 7338: 7325: 7318: 7304: 7290: 7281: 7275: 7260: 7253: 7237: 7234: 7233: 7232: 7226: 7211: 7208: 7205: 7204: 7178: 7111: 7086: 7050: 6998: 6959:(3): 809–814. 6939: 6872: 6795: 6742: 6689: 6636: 6595: 6558: 6541:Darling, David 6532: 6513: 6468: 6442: 6413: 6401: 6364: 6327:(3): 177–185. 6311: 6300: 6237: 6222: 6186: 6117: 6091: 6064: 6052:Universe Today 6042:Cain, Fraser; 6034: 6008: 5966:(4): 405–424. 5943: 5909:(2): 450–465. 5886: 5852: 5827: 5814:10.1086/118360 5774: 5763:on 15 May 2011 5743: 5726:solstation.com 5713: 5683: 5657: 5632: 5606: 5581: 5570:on 21 May 2019 5555: 5522:(5): 677–732, 5496: 5461: 5402: 5361: 5326:(2): 348–363. 5306: 5275: 5241: 5212: 5183: 5166:Darling, David 5157: 5135: 5110: 5043: 5017: 5008: 4977: 4932: 4906: 4869: 4867:, pp. 122–123. 4857: 4798: 4766: 4744: 4709:(2): 177–189. 4685: 4659: 4633: 4568: 4539: 4527: 4501: 4470: 4443: 4412: 4382: 4323: 4293: 4272:Darling, David 4260: 4245:10.1086/190414 4212: 4179: 4138: 4125:solstation.com 4112: 4078: 4027: 3985:(1): 108–128. 3959: 3933: 3862: 3848: 3819: 3785: 3758: 3736: 3713: 3680: 3645:(4): 413–420. 3626: 3596: 3557: 3529: 3508:10.1086/345779 3484:(1): 181–198. 3461: 3450:on 2 June 2016 3419:(2): 181–249. 3383: 3353: 3325: 3251: 3220: 3189: 3158: 3151: 3133: 3126: 3108: 3076: 3017: 2974: 2913: 2885: 2851: 2832:(3): 193–196. 2816: 2762: 2726: 2689: 2688: 2686: 2683: 2680: 2679: 2660: 2635: 2602: 2571: 2557: 2545:Drake equation 2527: 2526: 2524: 2521: 2519: 2518: 2512: 2503: 2497: 2491: 2485: 2480: 2473: 2467: 2461: 2455: 2453:Exoplanetology 2450: 2444: 2438: 2432: 2429:Habitable zone 2426: 2419: 2417: 2414: 2408: 2405: 2392:James Lovelock 2368: 2358: 2355: 2310: 2307: 2224:Main article: 2221: 2218: 2216: 2213: 2196: 2195: 2192: 2177: 2170: 2145: 2142: 2141: 2140: 2121: 2120: 2069: 2066: 2061:Main article: 2058: 2055: 2050:Main article: 2047: 2044: 2025: 2022: 2008: 2005: 1993:Barnard's Star 1976:chemosynthesis 1968:Photosynthesis 1962: 1959: 1948: 1941: 1910:photosynthesis 1906:habitable moon 1884: 1881: 1848:Main article: 1845: 1842: 1830:Alpha Centauri 1804:binary systems 1796:Main article: 1793: 1792:Binary systems 1790: 1761: 1758: 1747: 1746: 1740: 1734: 1724: 1721:psychroplanets 1718: 1707: 1704: 1701: 1700: 1685: 1662: 1657: 1653: 1646: 1592: 1586: 1585: 1547: 1540: 1539: 1511:Fixed nitrogen 1493: 1489: 1488: 1457: 1451: 1450: 1433: 1430: 1409:Atacama desert 1340:Atacama Desert 1331: 1328: 1320:origin of life 1267:carbon dioxide 1216:covalent bonds 1157: 1154: 1081: 1078: 1058: 1057: 1046: 1043: 1028:Snowball Earth 969:freezing point 959: 956: 932:magnetic field 867:carbon dioxide 772: 769: 763:, such as the 749:Hycean planets 657: 654: 606: 603: 590:Little Ice Age 549:Main article: 546: 543: 514:feedback loops 502: 475:Habitable zone 473:Main article: 470: 467: 435:habitable zone 405: 404: 397: 394: 379: 351:spectral class 346: 345:Spectral class 343: 286: 283: 267:Sun-like stars 205: 202: 67:. Life may be 15: 9: 6: 4: 3: 2: 11030: 11019: 11016: 11014: 11011: 11009: 11006: 11004: 11001: 10999: 10996: 10995: 10993: 10973: 10969: 10962: 10958: 10953: 10948: 10943: 10941: 10931: 10929: 10919: 10917: 10907: 10905: 10900: 10895: 10893: 10883: 10881: 10876: 10871: 10870: 10867: 10854: 10851: 10849: 10846: 10844: 10841: 10839: 10836: 10834: 10831: 10830: 10828: 10826:Organizations 10824: 10818: 10815: 10813: 10810: 10808: 10805: 10804: 10802: 10798: 10792: 10789: 10785: 10782: 10780: 10777: 10775: 10772: 10768: 10765: 10764: 10763: 10760: 10758: 10755: 10753: 10750: 10748: 10745: 10744: 10743: 10740: 10738: 10735: 10734: 10732: 10728: 10722: 10719: 10717: 10714: 10712: 10709: 10707: 10704: 10703: 10701: 10697: 10691: 10688: 10686: 10683: 10681: 10678: 10676: 10673: 10671: 10668: 10666: 10663: 10661: 10658: 10657: 10655: 10653:Core concepts 10651: 10647: 10640: 10635: 10633: 10628: 10626: 10621: 10620: 10617: 10605: 10602: 10600: 10597: 10596: 10593: 10587: 10584: 10582: 10579: 10577: 10574: 10572: 10569: 10567: 10564: 10562: 10559: 10557: 10554: 10552: 10549: 10547: 10544: 10542: 10539: 10537: 10534: 10532: 10529: 10528: 10526: 10522: 10514: 10511: 10509: 10506: 10504: 10501: 10499: 10496: 10494: 10491: 10489: 10486: 10484: 10481: 10479: 10476: 10474: 10471: 10469: 10466: 10464: 10461: 10459: 10456: 10454: 10451: 10449: 10446: 10444: 10441: 10439: 10436: 10434: 10431: 10430: 10428: 10427: 10422: 10419: 10417: 10414: 10412: 10409: 10405: 10402: 10400: 10397: 10395: 10392: 10390: 10387: 10386: 10385: 10382: 10380: 10377: 10375: 10372: 10370: 10367: 10365: 10362: 10360: 10357: 10355: 10352: 10350: 10347: 10346: 10345: 10342: 10341: 10336: 10333: 10331: 10328: 10326: 10323: 10322: 10320: 10319: 10317: 10315: 10311: 10305: 10302: 10300: 10297: 10295: 10292: 10290: 10287: 10285: 10282: 10280: 10277: 10276: 10274: 10270: 10264: 10261: 10259: 10256: 10254: 10251: 10249: 10246: 10244: 10241: 10239: 10236: 10234: 10231: 10229: 10226: 10224: 10221: 10219: 10216: 10214: 10211: 10209: 10206: 10204: 10201: 10199: 10196: 10194: 10191: 10189: 10186: 10184: 10181: 10180: 10178: 10176: 10172: 10166: 10163: 10159: 10156: 10155: 10154: 10151: 10147: 10144: 10143: 10142: 10139: 10135: 10132: 10131: 10130: 10127: 10125: 10122: 10118: 10115: 10114: 10113: 10110: 10106: 10103: 10102: 10101: 10098: 10096: 10093: 10092: 10090: 10088: 10084: 10078: 10077:Yellow giants 10075: 10073: 10070: 10068: 10065: 10063: 10060: 10058: 10055: 10053: 10050: 10048: 10045: 10043: 10040: 10038: 10035: 10033: 10030: 10028: 10025: 10023: 10020: 10018: 10015: 10013: 10010: 10008: 10005: 10003: 10000: 9999: 9997: 9995: 9991: 9983: 9980: 9978: 9975: 9973: 9970: 9968: 9965: 9964: 9962: 9960: 9957: 9953: 9950: 9949: 9948: 9945: 9941: 9938: 9937: 9936: 9933: 9932: 9930: 9928: 9924: 9918: 9915: 9913: 9910: 9908: 9905: 9903: 9900: 9898: 9895: 9893: 9890: 9888: 9885: 9883: 9880: 9878: 9875: 9873: 9870: 9868: 9865: 9863: 9860: 9858: 9855: 9853: 9850: 9848: 9847:Merging stars 9845: 9843: 9840: 9838: 9835: 9833: 9830: 9828: 9825: 9823: 9820: 9818: 9815: 9813: 9810: 9808: 9805: 9803: 9800: 9798: 9795: 9793: 9790: 9788: 9785: 9783: 9780: 9778: 9775: 9773: 9770: 9768: 9765: 9763: 9760: 9758: 9755: 9753: 9750: 9748: 9745: 9743: 9740: 9738: 9735: 9733: 9730: 9728: 9725: 9723: 9722:Asteroid belt 9720: 9718: 9715: 9713: 9710: 9709: 9707: 9705: 9697: 9687: 9684: 9682: 9679: 9677: 9674: 9672: 9669: 9667: 9664: 9662: 9661:Pulsar planet 9659: 9657: 9654: 9652: 9649: 9647: 9644: 9642: 9639: 9637: 9634: 9632: 9629: 9627: 9624: 9622: 9619: 9617: 9616:Double planet 9614: 9612: 9609: 9607: 9604: 9602: 9599: 9597: 9594: 9592: 9589: 9587: 9584: 9583: 9581: 9577: 9571: 9568: 9566: 9563: 9561: 9558: 9556: 9555:Super-Neptune 9553: 9551: 9550:Super-Jupiter 9548: 9546: 9543: 9541: 9538: 9536: 9533: 9531: 9528: 9526: 9525:Helium planet 9523: 9520: 9517: 9515: 9512: 9511: 9509: 9507: 9503: 9497: 9494: 9492: 9489: 9487: 9484: 9482: 9479: 9477: 9474: 9471: 9468: 9466: 9463: 9461: 9460:Hycean planet 9458: 9456: 9453: 9451: 9450:Desert planet 9448: 9446: 9443: 9441: 9440:Carbon planet 9438: 9437: 9435: 9433: 9429: 9426: 9424: 9416: 9411: 9401: 9398: 9396: 9393: 9391: 9388: 9386: 9383: 9381: 9378: 9377: 9375: 9371: 9365: 9362: 9356: 9353: 9352: 9351: 9348: 9347: 9346: 9343: 9342: 9339: 9330: 9325: 9323: 9318: 9316: 9311: 9310: 9307: 9295: 9292: 9290: 9287: 9285: 9282: 9280: 9277: 9275: 9272: 9270: 9267: 9265: 9262: 9260: 9257: 9255: 9252: 9250: 9247: 9245: 9242: 9240: 9237: 9235: 9232: 9230: 9227: 9225: 9222: 9220: 9217: 9215: 9212: 9210: 9207: 9205: 9202: 9200: 9197: 9196: 9194: 9192: 9188: 9182: 9179: 9177: 9174: 9172: 9169: 9167: 9164: 9162: 9159: 9157: 9154: 9152: 9149: 9147: 9144: 9142: 9139: 9137: 9134: 9133: 9131: 9128: 9127:Fermi paradox 9124: 9118: 9115: 9113: 9110: 9108: 9105: 9103: 9100: 9098: 9095: 9093: 9092:Fermi paradox 9090: 9088: 9085: 9083: 9080: 9078: 9075: 9073: 9070: 9069: 9067: 9063: 9057: 9054: 9052: 9051:Nordic aliens 9049: 9047: 9044: 9042: 9039: 9037: 9034: 9032: 9031:Energy beings 9029: 9028: 9026: 9024: 9018: 9012: 9009: 9007: 9004: 9002: 8999: 8997: 8994: 8992: 8989: 8987: 8984: 8982: 8979: 8977: 8974: 8972: 8969: 8967: 8964: 8962: 8959: 8957: 8954: 8952: 8949: 8947: 8944: 8942: 8939: 8937: 8934: 8930: 8927: 8925: 8922: 8921: 8920: 8917: 8915: 8912: 8910: 8907: 8905: 8902: 8900: 8897: 8895: 8892: 8890: 8887: 8886: 8884: 8882: 8881:communication 8876: 8870: 8869: 8865: 8863: 8862: 8858: 8856: 8853: 8851: 8848: 8846: 8843: 8841: 8839: 8835: 8833: 8830: 8828: 8826: 8822: 8820: 8818: 8814: 8812: 8809: 8807: 8804: 8802: 8799: 8797: 8794: 8792: 8789: 8787: 8784: 8782: 8779: 8777: 8774: 8772: 8769: 8767: 8764: 8762: 8759: 8757: 8754: 8750: 8748: 8744: 8743: 8742: 8739: 8737: 8736: 8732: 8730: 8727: 8725: 8722: 8720: 8719: 8715: 8713: 8712: 8708: 8706: 8704: 8700: 8698: 8695: 8693: 8690: 8688: 8685: 8684: 8682: 8680: 8676: 8670: 8667: 8665: 8662: 8660: 8657: 8655: 8652: 8650: 8647: 8645: 8642: 8640: 8637: 8635: 8632: 8630: 8627: 8625: 8622: 8620: 8617: 8615: 8612: 8610: 8607: 8605: 8602: 8600: 8597: 8595: 8592: 8591: 8589: 8587: 8581: 8575: 8574:Life on Titan 8572: 8570: 8567: 8565: 8564:Life on Venus 8562: 8560: 8557: 8555: 8552: 8551: 8549: 8545: 8532: 8529: 8524: 8521: 8516: 8513: 8508: 8505: 8504: 8502: 8498: 8489: 8486: 8481: 8478: 8473: 8470: 8465: 8462: 8461: 8459: 8455: 8446: 8443: 8438: 8435: 8434: 8432: 8430:Misidentified 8428: 8425: 8421: 8414: 8411: 8408: 8407:Yamato 000593 8405: 8402: 8399: 8396: 8393: 8390: 8387: 8384: 8381: 8378: 8375: 8372: 8369: 8368: 8366: 8362: 8358: 8351: 8346: 8344: 8339: 8337: 8332: 8331: 8328: 8316: 8315: 8306: 8304: 8303: 8294: 8293: 8290: 8284: 8281: 8279: 8276: 8274: 8271: 8269: 8266: 8264: 8261: 8259: 8256: 8254: 8251: 8249: 8246: 8242: 8239: 8237: 8234: 8232: 8229: 8228: 8227: 8224: 8222: 8219: 8217: 8214: 8213: 8211: 8205: 8195: 8192: 8190: 8187: 8185: 8182: 8180: 8177: 8175: 8172: 8170: 8167: 8165: 8162: 8160: 8157: 8155: 8152: 8150: 8147: 8146: 8144: 8138: 8132: 8129: 8127: 8124: 8122: 8119: 8117: 8114: 8112: 8109: 8107: 8104: 8102: 8099: 8097: 8094: 8092: 8089: 8087: 8084: 8082: 8081:Europa Lander 8079: 8077: 8074: 8072: 8069: 8067: 8064: 8062: 8059: 8057: 8054: 8052: 8049: 8047: 8044: 8043: 8041: 8037: 8029: 8027: 8023: 8022: 8021: 8018: 8016: 8013: 8011: 8010: 8006: 8005: 8003: 7999: 7993: 7990: 7989: 7987: 7983: 7977: 7976: 7972: 7970: 7967: 7965: 7964: 7960: 7959: 7957: 7951: 7945: 7942: 7940: 7937: 7933: 7931: 7927: 7926: 7925: 7922: 7920: 7919: 7915: 7911: 7909: 7905: 7904: 7903: 7900: 7896: 7894: 7890: 7889: 7888: 7885: 7883: 7880: 7878: 7875: 7874: 7872: 7868: 7862: 7859: 7857: 7854: 7852: 7849: 7847: 7844: 7842: 7839: 7837: 7834: 7832: 7829: 7827: 7824: 7822: 7819: 7817: 7814: 7812: 7809: 7807: 7804: 7802: 7799: 7797: 7794: 7792: 7789: 7787: 7784: 7783: 7781: 7777: 7774: 7768: 7762: 7759: 7757: 7754: 7752: 7749: 7747: 7744: 7742: 7739: 7737: 7734: 7732: 7729: 7727: 7724: 7722: 7719: 7717: 7714: 7712: 7709: 7707: 7704: 7702: 7699: 7697: 7694: 7692: 7689: 7688: 7686: 7684: 7678: 7672: 7669: 7667: 7664: 7662: 7659: 7657: 7654: 7652: 7649: 7647: 7644: 7642: 7639: 7637: 7636:Extremophiles 7634: 7632: 7629: 7627: 7624: 7622: 7619: 7617: 7614: 7612: 7609: 7607: 7604: 7602: 7599: 7597: 7594: 7592: 7589: 7588: 7586: 7582: 7576: 7573: 7571: 7568: 7566: 7563: 7561: 7558: 7556: 7553: 7551: 7548: 7546: 7543: 7541: 7538: 7536: 7533: 7531: 7528: 7526: 7523: 7522: 7520: 7516: 7512: 7505: 7500: 7498: 7493: 7491: 7486: 7485: 7482: 7476: 7473: 7471: 7468: 7466: 7463: 7460: 7456: 7453: 7450: 7446: 7443: 7441: 7438: 7436: 7433: 7432: 7428: 7424: 7409: 7365: 7361: 7357: 7353: 7351: 7350:0-471-13561-5 7347: 7343: 7339: 7337: 7336:0-19-286218-9 7333: 7330: 7326: 7323: 7319: 7317: 7316:0-89526-065-4 7313: 7309: 7305: 7303: 7302:1-56091-609-5 7299: 7295: 7291: 7288: 7287: 7282: 7278: 7272: 7268: 7267: 7261: 7258: 7254: 7252: 7251:0-09-187927-2 7248: 7244: 7240: 7239: 7229: 7223: 7219: 7214: 7213: 7193: 7189: 7182: 7175: 7170: 7164: 7160: 7156: 7152: 7147: 7142: 7138: 7134: 7130: 7126: 7122: 7115: 7100: 7096: 7090: 7082: 7076: 7060: 7054: 7047: 7043: 7039: 7035: 7031: 7027: 7022: 7017: 7013: 7009: 7002: 6994: 6990: 6985: 6980: 6975: 6970: 6966: 6962: 6958: 6954: 6950: 6943: 6935: 6931: 6926: 6921: 6917: 6913: 6908: 6903: 6899: 6895: 6891: 6887: 6883: 6876: 6868: 6864: 6859: 6854: 6850: 6846: 6841: 6836: 6832: 6828: 6823: 6818: 6814: 6810: 6806: 6799: 6791: 6787: 6783: 6779: 6775: 6771: 6766: 6761: 6757: 6753: 6746: 6738: 6734: 6730: 6726: 6722: 6718: 6713: 6708: 6704: 6700: 6693: 6685: 6681: 6677: 6673: 6669: 6665: 6660: 6655: 6651: 6647: 6640: 6631: 6626: 6622: 6618: 6614: 6610: 6606: 6599: 6591: 6585: 6569: 6562: 6546: 6542: 6536: 6528: 6524: 6517: 6509: 6505: 6501: 6497: 6493: 6489: 6485: 6481: 6480: 6472: 6457: 6453: 6446: 6438: 6434: 6430: 6426: 6425: 6417: 6410: 6405: 6397: 6391: 6375: 6368: 6360: 6356: 6352: 6348: 6344: 6340: 6335: 6330: 6326: 6322: 6315: 6309: 6304: 6296: 6292: 6288: 6284: 6279: 6274: 6270: 6266: 6261: 6256: 6252: 6248: 6247:New Astronomy 6241: 6233: 6226: 6218: 6212: 6196: 6190: 6175: 6171: 6166: 6161: 6156: 6151: 6147: 6143: 6139: 6135: 6128: 6121: 6106: 6102: 6095: 6079: 6075: 6068: 6053: 6049: 6045: 6038: 6023: 6022:New Scientist 6019: 6012: 5997: 5993: 5989: 5985: 5981: 5977: 5973: 5969: 5965: 5961: 5954: 5947: 5928: 5924: 5920: 5916: 5912: 5908: 5904: 5897: 5890: 5874: 5870: 5866: 5862: 5856: 5841: 5837: 5831: 5823: 5819: 5815: 5811: 5807: 5803: 5798: 5793: 5789: 5785: 5778: 5762: 5758: 5754: 5747: 5731: 5727: 5723: 5717: 5701: 5697: 5693: 5687: 5672: 5668: 5661: 5646: 5642: 5636: 5621: 5617: 5610: 5595: 5591: 5585: 5569: 5565: 5559: 5545: 5541: 5537: 5533: 5529: 5525: 5521: 5517: 5510: 5503: 5501: 5492: 5488: 5484: 5480: 5477:(1): 91–101. 5476: 5472: 5465: 5457: 5453: 5449: 5445: 5441: 5437: 5433: 5429: 5425: 5421: 5417: 5413: 5406: 5387: 5383: 5379: 5372: 5365: 5357: 5353: 5349: 5345: 5341: 5337: 5333: 5329: 5325: 5321: 5317: 5310: 5294: 5290: 5286: 5279: 5263: 5259: 5255: 5251: 5245: 5230: 5226: 5222: 5216: 5201: 5197: 5193: 5187: 5171: 5167: 5161: 5145: 5139: 5124: 5120: 5114: 5106: 5102: 5098: 5094: 5089: 5084: 5080: 5076: 5071: 5066: 5062: 5058: 5054: 5047: 5032: 5028: 5025:Woo, Marcus. 5021: 5012: 5005: 4992: 4988: 4981: 4973: 4969: 4965: 4961: 4957: 4953: 4949: 4945: 4944: 4936: 4920: 4916: 4910: 4902: 4896: 4880: 4873: 4866: 4861: 4853: 4849: 4844: 4839: 4835: 4831: 4826: 4821: 4817: 4813: 4809: 4802: 4787: 4783: 4782: 4777: 4770: 4754: 4748: 4740: 4736: 4732: 4728: 4724: 4720: 4716: 4712: 4708: 4704: 4700: 4696: 4689: 4673: 4669: 4663: 4647: 4643: 4637: 4629: 4625: 4621: 4617: 4613: 4609: 4605: 4601: 4596: 4591: 4587: 4583: 4579: 4572: 4557: 4553: 4549: 4543: 4537:, pp. 191–220 4536: 4531: 4516: 4512: 4505: 4490: 4489: 4484: 4480: 4474: 4458: 4454: 4447: 4431: 4427: 4423: 4416: 4400: 4396: 4392: 4386: 4378: 4374: 4370: 4366: 4362: 4358: 4353: 4348: 4344: 4340: 4339: 4330: 4328: 4311: 4307: 4303: 4297: 4281: 4277: 4273: 4267: 4265: 4255: 4250: 4246: 4242: 4238: 4234: 4230: 4226: 4219: 4217: 4200: 4196: 4192: 4186: 4184: 4164: 4160: 4156: 4149: 4142: 4127:. Sol Company 4126: 4122: 4116: 4100: 4096: 4092: 4088: 4082: 4074: 4070: 4066: 4062: 4058: 4054: 4050: 4046: 4042: 4038: 4031: 4012: 4008: 4004: 4000: 3996: 3992: 3988: 3984: 3980: 3973: 3969: 3963: 3948: 3944: 3937: 3929: 3925: 3920: 3915: 3911: 3907: 3903: 3899: 3894: 3889: 3886:(8): 715–39. 3885: 3881: 3877: 3873: 3866: 3858: 3852: 3837: 3833: 3826: 3824: 3807: 3803: 3799: 3792: 3790: 3773: 3769: 3762: 3746: 3740: 3724: 3717: 3710: 3697: 3690: 3684: 3676: 3672: 3668: 3664: 3660: 3656: 3652: 3648: 3644: 3640: 3636: 3630: 3614: 3610: 3606: 3605:"Star tables" 3600: 3592: 3586: 3578: 3574: 3570: 3569: 3561: 3546: 3545: 3540: 3533: 3521: 3517: 3513: 3509: 3505: 3501: 3497: 3492: 3487: 3483: 3479: 3472: 3465: 3446: 3442: 3438: 3434: 3430: 3426: 3422: 3418: 3414: 3407: 3400: 3398: 3396: 3394: 3392: 3390: 3388: 3372: 3368: 3362: 3360: 3358: 3342: 3341: 3336: 3329: 3321: 3317: 3312: 3307: 3302: 3297: 3293: 3289: 3284: 3279: 3275: 3271: 3270: 3265: 3258: 3256: 3240: 3239: 3234: 3227: 3225: 3209: 3208: 3203: 3199: 3193: 3178: 3177: 3172: 3168: 3162: 3154: 3148: 3145:. Wiley-VCH. 3144: 3137: 3129: 3123: 3119: 3112: 3096: 3095: 3087: 3080: 3072: 3068: 3064: 3060: 3056: 3052: 3048: 3044: 3040: 3036: 3032: 3028: 3021: 3013: 3009: 3005: 3001: 2997: 2993: 2989: 2985: 2978: 2970: 2966: 2961: 2956: 2952: 2948: 2943: 2938: 2934: 2930: 2929: 2924: 2917: 2902: 2901: 2896: 2889: 2873: 2869: 2865: 2861: 2855: 2847: 2843: 2839: 2835: 2831: 2827: 2820: 2812: 2808: 2804: 2800: 2796: 2792: 2788: 2784: 2780: 2776: 2769: 2767: 2755: 2748: 2747: 2739: 2737: 2735: 2733: 2731: 2714: 2710: 2709: 2704: 2697: 2695: 2690: 2675: 2671: 2664: 2657: 2653: 2649: 2645: 2639: 2631: 2626: 2622: 2618: 2617: 2612: 2611:extremophiles 2606: 2599: 2595: 2591: 2587: 2583: 2582: 2575: 2567: 2561: 2554: 2550: 2549:Fermi paradox 2546: 2542: 2538: 2532: 2528: 2516: 2513: 2507: 2504: 2501: 2498: 2495: 2492: 2489: 2486: 2484: 2481: 2479: 2478: 2474: 2471: 2468: 2465: 2462: 2459: 2456: 2454: 2451: 2448: 2445: 2442: 2439: 2436: 2433: 2430: 2427: 2424: 2421: 2420: 2413: 2404: 2402: 2397: 2393: 2389: 2385: 2381: 2377: 2376:cyanobacteria 2374:) by ancient 2354: 2351: 2347: 2343: 2338: 2336: 2331: 2330:asteroid belt 2325: 2322: 2320: 2316: 2306: 2304: 2300: 2296: 2292: 2287: 2285: 2281: 2277: 2273: 2269: 2265: 2261: 2257: 2253: 2250: 2249:mathematician 2246: 2243: 2239: 2238: 2233: 2227: 2212: 2208: 2206: 2202: 2193: 2190: 2186: 2182: 2178: 2175: 2171: 2168: 2163: 2159: 2158: 2157: 2155: 2151: 2137: 2133: 2129: 2128: 2127: 2125: 2118: 2114: 2110: 2106: 2102: 2101: 2100: 2098: 2094: 2090: 2087: 2083: 2081: 2077: 2073: 2064: 2053: 2046:Neutron stars 2043: 2040: 2035: 2032: 2024:Massive stars 2021: 2017: 2014:billion years 2004: 2002: 1998: 1997:stellar flare 1994: 1988: 1985: 1980: 1977: 1973: 1969: 1958: 1956: 1952: 1944: 1937: 1933: 1926: 1922: 1917: 1913: 1911: 1907: 1903: 1899: 1898:Lacaille 8760 1895: 1890: 1880: 1877: 1869: 1865: 1861: 1856: 1851: 1841: 1839: 1835: 1831: 1828:One study of 1826: 1824: 1820: 1816: 1812: 1807: 1805: 1799: 1789: 1787: 1783: 1779: 1775: 1771: 1766: 1757: 1754: 1752: 1751:extremophilic 1744: 1741: 1738: 1737:thermoplanets 1735: 1732: 1728: 1725: 1722: 1719: 1716: 1713: 1712: 1711: 1698: 1694: 1688: 1681: 1675: 1669: 1660: 1649: 1642: 1636: 1632: 1628: 1623: 1619: 1613: 1609: 1603: 1597: 1593: 1588: 1587: 1584: 1580: 1575: 1571: 1566: 1562: 1557:(subsurface) 1556: 1551: 1548: 1546: 1542: 1541: 1537: 1531: 1527: 1522: 1517: 1512: 1508: 1502: 1497: 1494: 1491: 1490: 1486: 1482: 1478: 1474: 1468: 1462: 1458: 1456: 1453: 1452: 1449: 1445: 1442: 1440: 1429: 1427: 1426:biosignatures 1423: 1419: 1414: 1410: 1406: 1401: 1399: 1394: 1388: 1386: 1382: 1378: 1374: 1370: 1369:Extremophiles 1366: 1365:genetic drift 1362: 1358: 1349: 1345: 1344:South America 1341: 1336: 1327: 1323: 1321: 1316: 1311: 1306: 1304: 1300: 1296: 1292: 1288: 1284: 1280: 1276: 1272: 1268: 1264: 1260: 1256: 1252: 1247: 1245: 1241: 1237: 1233: 1229: 1225: 1221: 1217: 1213: 1209: 1205: 1201: 1197: 1193: 1189: 1185: 1181: 1177: 1173: 1169: 1163: 1153: 1151: 1145: 1143: 1139: 1135: 1131: 1127: 1123: 1119: 1115: 1114:radionuclides 1108: 1086: 1077: 1075: 1070: 1067: 1063: 1055: 1051: 1047: 1044: 1040: 1039: 1038: 1035: 1031: 1029: 1025: 1021: 1017: 1013: 1009: 1004: 1002: 998: 994: 990: 985: 981: 979: 974: 973:boiling point 970: 965: 955: 951: 949: 948:dynamo effect 945: 941: 937: 933: 928: 924: 921: 917: 913: 909: 907: 903: 899: 894: 892: 887: 883: 878: 876: 872: 871:bio-diversity 868: 864: 860: 856: 852: 848: 843: 841: 837: 833: 829: 825: 821: 817: 816:heat transfer 813: 809: 805: 801: 797: 793: 785: 781: 777: 771:Mass and size 768: 766: 762: 758: 754: 753:biosignatures 750: 746: 745:ocean planets 741: 738: 734: 729: 727: 723: 718: 716: 712: 708: 704: 700: 696: 692: 688: 684: 680: 676: 671: 670:biosignatures 662: 653: 651: 646: 642: 641:Spectroscopic 638: 634: 630: 626: 622: 618: 612: 602: 600: 596: 595:solar analogs 591: 587: 583: 578: 575: 571: 567: 563: 558: 552: 551:Variable star 542: 540: 536: 532: 527: 522: 519: 515: 509: 494: 489: 486: 482: 476: 466: 462: 458: 456: 452: 448: 444: 440: 436: 432: 428: 424: 420: 415: 413: 409: 402: 401:tidal locking 398: 395: 392: 388: 384: 380: 377: 373: 372: 371: 369: 364: 360: 357:, which (for 356: 352: 342: 339: 335: 331: 326: 324: 319: 315: 311: 307: 304:, scientists 303: 299: 294: 292: 282: 280: 276: 272: 268: 264: 260: 257: 253: 252:space mission 251: 246: 245:extremophiles 242: 238: 233: 231: 227: 222: 219: 215: 211: 201: 199: 195: 191: 187: 184:. Rocky, wet 183: 179: 175: 171: 167: 163: 159: 158:biosignatures 154: 152: 148: 144: 140: 136: 135:astrophysical 132: 128: 124: 119: 117: 113: 109: 105: 101: 100:multicellular 97: 93: 89: 88:extrapolation 85: 80: 78: 74: 70: 66: 62: 58: 54: 50: 43: 39: 35: 30: 26: 22: 11003:Astrobiology 10975:. Retrieved 10971: 10961: 10940:Solar System 10833:Mars Society 10742:Solar System 10690:Terraforming 10674: 10421:Proper names 10198:Earth analog 10183:Astrobiology 10175:Habitability 10174: 10112:Microlensing 10072:White dwarfs 10042:M/Red dwarfs 10032:Herbig Ae/Be 10017:Brown dwarfs 9959:Rogue planet 9940:Interstellar 9882:Planetesimal 9651:Planetesimal 9631:Giant planet 9621:Ecumenopolis 9519:Mini-Neptune 9455:Dwarf planet 9289:UFO religion 9234:Extremophile 9214:Biosignature 9209:Astroecology 9204:Astrobiology 9156:Great Filter 8971:Project Ozma 8879:Interstellar 8866: 8859: 8837: 8825:Perseverance 8824: 8816: 8746: 8733: 8716: 8709: 8702: 8658: 8604:Earth analog 8586:habitability 8583: 8569:Life on Mars 8312: 8300: 8209:and programs 8207:Institutions 8025: 8007: 7985:Heliocentric 7973: 7961: 7929: 7916: 7908:Perseverance 7907: 7892: 7696:Earth analog 7683:habitability 7680: 7651:Ocean planet 7621:Earth analog 7606:Biosignature 7565:Paleontology 7560:Microbiology 7540:Biochemistry 7530:Astrophysics 7511:Astrobiology 7355: 7341: 7328: 7321: 7307: 7293: 7289:, April 1991 7284: 7265: 7256: 7242: 7220:. 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Retrieved 2713:the original 2706: 2673: 2663: 2638: 2614: 2605: 2579: 2574: 2566:have emerged 2560: 2531: 2515:Terraforming 2475: 2441:Earth analog 2410: 2360: 2339: 2326: 2323: 2312: 2299:neutron star 2288: 2276:hydrocarbons 2256:astrobiology 2235: 2229: 2209: 2197: 2147: 2123: 2122: 2092: 2091: 2085: 2084: 2075: 2074: 2071: 2036: 2031:brown dwarfs 2027: 2018: 2010: 1989: 1981: 1964: 1929: 1886: 1873: 1827: 1808: 1801: 1767: 1763: 1755: 1748: 1742: 1736: 1726: 1720: 1714: 1709: 1692: 1679: 1673: 1667: 1640: 1626: 1620: Strong 1617: 1607: 1601: 1595: 1578: 1569: 1560: 1554: 1549: 1535: 1530:Heavy metals 1525: 1520: 1515: 1506: 1500: 1495: 1472: 1466: 1460: 1447: 1435: 1404: 1402: 1389: 1377:alkaliphilic 1353: 1324: 1307: 1248: 1246:) are rare. 1168:biochemistry 1165: 1162:Geochemistry 1156:Geochemistry 1146: 1111: 1071: 1066:crucial role 1060:The Earth's 1059: 1036: 1032: 1023: 1005: 986: 982: 961: 952: 940:stellar wind 929: 925: 910: 895: 891:super-Earths 879: 851:geologically 844: 812:biochemistry 789: 742: 730: 719: 667: 633:solar nebula 614: 579: 554: 523: 516:such as the 510: 490: 485:Su-Shu Huang 478: 463: 459: 455:Gliese 163 c 447:Gliese 581 g 443:Gliese 581 d 437:" (HZ) of a 427:Gliese 581 c 416: 408:K-type stars 406: 348: 334:geodynamical 327: 295: 288: 249: 234: 207: 164:properties, 155: 151:water worlds 120: 116:astrobiology 96:Solar System 81: 48: 47: 25: 10928:Outer space 10916:Spaceflight 10706:Bishop Ring 10433:before 2000 10349:Discoveries 10124:Polarimetry 10012:Binary star 9902:Rubble pile 9897:Ring system 9867:Outer space 9837:Kuiper belt 9792:Hills cloud 9747:Debris disk 9742:Cosmic dust 9671:Sub-Neptune 9656:Protoplanet 9591:Brown dwarf 9579:Other types 9535:Hot Neptune 9530:Hot Jupiter 9521:(Gas dwarf) 9496:Super-Earth 9481:Ocean world 9476:Lava planet 9470:Iron planet 9432:Terrestrial 9373:Main topics 9224:Exotheology 9036:Grey aliens 8889:Active SETI 8817:Opportunity 8697:BioSentinel 8515:Wow! signal 8464:KIC 8462852 8413:CI1 fossils 8142:undeveloped 7992:BioSentinel 7882:Fobos-Grunt 7779:Earth orbit 7601:Biomolecule 7591:Abiogenesis 7584:Main topics 7518:Disciplines 7475:Sol Station 7459:UPR Arecibo 7449:UPR Arecibo 6758:(1): 1–10. 6551:5 September 6044:Gay, Pamela 5676:19 November 5150:20 December 5128:28 December 3952:14 December 3872:Bitz, C. M. 3371:phl.upr.edu 3182:20 November 2906:1 September 2656:Super-Earth 2590:Ian Stewart 2423:Astrobotany 2384:respiration 2291:Frank Drake 2252:Ian Stewart 2205:Kuiper belt 1864:Gliese 229A 1765:the Sun's. 1731:mesoplanets 1727:mesoplanets 1555:Geochemical 1543:Energy for 1381:acidophilic 1303:amino acids 1295:atmospheres 1220:amino acids 1198:and in the 1188:amino acids 1130:solar winds 1074:ocean tides 1012:homeostasis 1010:to achieve 886:radioactive 859:earthquakes 782:, with its 759:as well as 724:released a 687:terrestrial 611:Metallicity 582:solar cycle 574:Atmospheres 555:Changes in 431:super-Earth 330:geophysical 310:Jill Tarter 279:light-years 273:within the 256:Earth-sized 221:exploration 212:as much as 186:terrestrial 182:metallicity 180:, and high 178:variability 131:geochemical 127:geophysical 104:unicellular 10992:Categories 10791:Free space 10344:Exoplanets 10325:Host stars 10272:Catalogues 10095:Astrometry 10057:Subdwarf B 9994:Host stars 9967:Retrograde 9862:Oort cloud 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808:solar wind 796:atmosphere 711:gas giants 695:Earth mass 645:exoplanets 635:theory of 609:See also: 599:18 Scorpii 557:luminosity 451:Gliese 163 391:ionisation 271:red dwarfs 241:exoplanets 226:exoplanets 210:philosophy 204:Background 196:and other 174:luminosity 166:atmosphere 147:metabolism 73:panspermia 10892:Astronomy 10762:Asteroids 10438:2000–2009 10404:1501–2000 10399:1001–1500 10087:Detection 10052:Red giant 9712:Accretion 9704:evolution 9545:Ice giant 9540:Gas giant 9491:Sub-Earth 9380:Exoplanet 9129:solutions 8996:setiQuest 8991:SETI@home 8806:Mars 2020 8781:Laplace-P 8718:Dragonfly 8703:Curiosity 8584:Planetary 8106:Laplace-P 8009:Dragonfly 7963:Hayabusa2 7955:asteroids 7924:Tianwen-1 7902:Mars 2020 7893:Curiosity 7826:Eu:CROPIS 7681:Planetary 7174:CC BY 4.0 7163:228086341 7155:2662-4435 7131:(1): 61. 7046:118574839 7021:1106.2800 6916:0027-8424 6849:0027-8424 6765:0911.4381 6712:0903.3305 6659:0806.2795 6523:Astronomy 6424:Astronomy 6359:118534798 6334:1212.0113 6295:119255193 6273:CiteSeerX 6260:1002.4693 6084:10 August 6001:11 August 5395:26 August 5289:Space.com 5105:226289878 5097:2041-8213 4852:195584241 4818:(1): 60. 4759:16 August 4731:1531-1074 4520:27 August 4494:25 August 4352:1102.0541 4345:(1): 19. 4172:11 August 3893:1305.6926 3836:Space.com 3729:27 August 3619:12 August 3585:cite book 3550:24 August 3544:Space.com 3441:123220355 3376:19 August 3283:1311.6806 3213:6 January 2935:(1): 75. 2878:11 August 2811:206546351 2447:Exoplanet 2242:biologist 2181:magnetars 2174:gamma ray 2154:Orion Arm 2117:biosphere 2113:Enceladus 2093:Class III 2039:supernova 1984:starspots 1921:GJ 667 Cc 1876:red dwarf 1819:Alan Boss 1612:anaerobes 1361:selection 1308:Even so, 1008:biosphere 855:volcanoes 847:diameters 828:radiation 800:molecules 709:found on 683:accretion 566:gamma ray 562:organisms 526:gas giant 518:CNO cycle 439:red dwarf 419:red dwarf 323:Milky Way 291:host star 275:Milky Way 176:, stable 108:astronomy 10977:13 April 10394:501–1000 10374:Heaviest 10354:Extremes 10062:Subgiant 9935:Exocomet 8981:SERENDIP 8956:NIROSETI 8868:Viking 2 8861:Viking 1 8766:Foton-M3 8756:ExoLance 8687:Beagle 2 8302:Category 8164:Kazachok 8154:Beagle 3 8086:ExoLance 8039:Proposed 7877:Beagle 2 7851:OREOcube 7831:EXOSTACK 7772:missions 7425: · 7099:phys.org 7075:cite web 7065:6 August 6993:11158551 6934:25825762 6867:25831540 6584:cite web 6574:5 August 6508:22017274 6461:20 March 6456:NBC News 6390:cite web 6380:5 August 6211:cite web 6201:5 August 6174:19487662 6046:(2007). 6027:5 August 5996:12329736 5988:10472629 5845:31 March 5822:18969130 5650:31 March 5625:19 April 5599:19 April 5544:17067257 5456:18220447 5448:14605363 5356:20466013 5348:16689651 5299:6 August 5268:6 August 5123:phys.org 4895:cite web 4739:38306187 4678:19 April 4628:10257401 4620:17407404 4515:BBC News 4488:Phys.org 4377:15233153 4316:5 August 4286:6 August 4205:5 August 4020:6 August 4007:11536936 3928:23855332 3667:11536831 3613:Archived 3516:14734094 3320:24191033 3071:19621191 3063:17732735 2969:46991835 2803:23641111 2416:See also 2270:, while 2139:diluted. 2136:Callisto 2132:Ganymede 2124:Class IV 2086:Class II 1972:infrared 1565:Oxidants 1477:Salinity 1373:inimical 1357:mutation 1310:volcanic 1263:nitrogen 1259:hydrogen 1224:proteins 1190:such as 1184:nitrogen 1176:hydrogen 1001:ecliptic 900:'s moon 784:rarefied 733:bacteria 703:hydrogen 699:silicate 650:universe 617:hydrogen 586:evidence 376:luminous 325:galaxy. 55:'s or a 10952:Science 10880:Biology 10866:Portals 10747:Mercury 10369:Largest 10364:Nearest 10067:T Tauri 9963:Orbits 9947:Exomoon 9927:Systems 9641:Planemo 9506:Gaseous 8845:Tanpopo 8741:ExoMars 8445:CTA-102 8437:CP 1919 8314:Commons 8131:Trident 8121:Oceanus 8020:ExoMars 8001:Planned 7975:Rosetta 7930:Zhurong 7918:Phoenix 7856:Tanpopo 7846:O/OREOS 7791:BIOCORE 7412: ( 7383:minutes 7133:Bibcode 7026:Bibcode 6961:Bibcode 6925:4394300 6894:Bibcode 6858:4394287 6827:Bibcode 6790:1103987 6770:Bibcode 6737:8032181 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The 2176:source. 2076:Class I 1894:Mercury 1868:Aurelia 1821:at the 1815:Nemesis 1697:aeolian 1287:silicon 1279:ammonia 1275:methane 1204:biomass 1192:glycine 1080:Geology 993:seasons 978:Mercury 936:protect 920:methane 898:Jupiter 840:inch Hg 834:, 4.56 792:gravity 737:archaea 259:planets 162:orbital 61:develop 10848:SpaceX 10817:Europa 10767:mining 10384:Kepler 10359:Firsts 10258:Tholin 10129:Timing 10047:Pulsar 9972:Trojan 9586:Blanet 9345:Planet 9249:MERMOZ 8838:Spirit 8761:EXPOSE 8711:Darwin 8669:Tholin 8415:(2011) 8409:(2000) 8403:(1984) 8397:(1977) 8391:(1976) 8385:(1969) 8379:(1911) 8373:(1865) 8263:MERMOZ 8056:CAESAR 7944:Viking 7861:VEGGIE 7836:EXPOSE 7816:E-MIST 7806:BIOPAN 7796:Biolab 7756:Tholin 7362: 7348: 7334: 7314: 7300: 7273: 7249: 7224: 7161: 7153: 7044: 6991: 6981: 6932: 6922: 6914: 6865: 6855: 6847: 6788: 6735: 6682: 6506: 6357: 6293: 6275: 6172: 6162: 6110:5 June 5994: 5986: 5903:Icarus 5879:11 May 5820: 5767:5 June 5736:5 June 5706:5 June 5549:6 June 5542: 5454: 5446: 5438: 5354: 5346: 5234:11 May 5205:11 May 5176:11 May 5103: 5095: 4970: 4943:Nature 4925:11 May 4885:8 June 4850: 4791:11 May 4737: 4729: 4652:4 June 4648:. 2008 4626: 4618: 4561:11 May 4552:Geolab 4375: 4312:. 2002 4131:11 May 4105:11 May 4071: 4063: 4037:Nature 4005: 3979:Icarus 3926: 3916: 3709:color. 3673: 3665: 3575: 3514: 3439: 3318: 3308: 3149: 3124: 3101:7 July 3069: 3061: 3053: 3010: 2984:Nature 2967: 2809: 2801: 2672:). In 2644:Uranus 2633:occur. 2335:Saturn 2254:argue 2109:Europa 1753:life. 1693:· 1691: 1680:· 1678: 1674:· 1672: 1668:· 1666: 1641:· 1639: 1627:· 1625: 1618:· 1616: 1608:· 1606: 1602:· 1600: 1596:· 1594: 1581: 1579:· 1577: 1572: 1570:· 1568: 1563: 1561:· 1559: 1536:· 1534: 1528: 1526:· 1524: 1516:· 1514: 1507:· 1505: 1501:· 1499: 1483:, and 1475: 1473:· 1471: 1467:· 1465: 1461:· 1459: 1418:Viking 1405:cannot 1363:, and 1315:Comets 1297:. The 1283:silica 1251:oxygen 1228:sulfur 1182:, and 1180:oxygen 1172:carbon 912:Saturn 906:Europa 794:makes 707:helium 625:metals 621:helium 338:plasma 314:HabCat 250:Kepler 133:, and 123:energy 53:planet 38:planet 10904:Stars 10812:Venus 10779:Titan 10752:Venus 10524:Other 10389:1–500 10314:Lists 9423:types 9418:Sizes 8840:rover 8827:rover 8819:rover 8749:rover 8705:rover 8500:Other 8457:Stars 8179:MELOS 8051:BRUIE 8028:rover 7932:rover 7910:rover 7895:rover 7770:Space 7457:(PHL/ 7447:(PHL/ 7159:S2CID 7042:S2CID 7016:arXiv 6984:14664 6817:arXiv 6786:S2CID 6760:arXiv 6733:S2CID 6707:arXiv 6680:S2CID 6654:arXiv 6355:S2CID 6329:arXiv 6291:S2CID 6255:arXiv 6130:(PDF) 5992:S2CID 5956:(PDF) 5930:(PDF) 5899:(PDF) 5818:S2CID 5792:arXiv 5512:(PDF) 5452:S2CID 5436:JSTOR 5389:(PDF) 5374:(PDF) 5352:S2CID 5101:S2CID 5065:arXiv 4997:1 May 4968:S2CID 4848:S2CID 4820:arXiv 4624:S2CID 4590:arXiv 4373:S2CID 4347:arXiv 4166:(PDF) 4151:(PDF) 4069:S2CID 4014:(PDF) 3975:(PDF) 3888:arXiv 3702:1 May 3671:S2CID 3523:(PDF) 3512:S2CID 3486:arXiv 3474:(PDF) 3454:3 May 3448:(PDF) 3437:S2CID 3409:(PDF) 3278:arXiv 3089:(PDF) 3067:S2CID 3051:JSTOR 3008:S2CID 2965:S2CID 2937:arXiv 2807:S2CID 2757:(PDF) 2750:(PDF) 2523:Notes 1650:, O, 1629: 1550:Solar 1509: 1455:Water 1255:crust 1208:cells 1042:fore. 916:Titan 836:mm Hg 570:X-ray 531:Venus 481:shell 429:, a " 387:ozone 230:stars 34:Earth 10979:2023 10972:NASA 10838:NASA 10807:Mars 10774:Moon 10757:Mars 10513:2024 10508:2023 10503:2022 10498:2021 10493:2020 10488:2019 10483:2018 10478:2017 10473:2016 10468:2015 10463:2014 10458:2013 10453:2012 10448:2011 10443:2010 10158:list 10146:list 10134:list 10117:list 10105:list 9702:and 9420:and 8531:BLC1 8126:THEO 7870:Mars 7801:Bion 7360:ISBN 7346:ISBN 7332:ISBN 7312:ISBN 7298:ISBN 7271:ISBN 7257:NASA 7247:ISBN 7222:ISBN 7199:2021 7151:ISSN 7106:2021 7081:link 7067:2007 6989:PMID 6930:PMID 6912:ISSN 6863:PMID 6845:ISSN 6590:link 6576:2007 6553:2009 6504:PMID 6463:2015 6409:Ward 6396:link 6382:2007 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