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radioactivity counter would detect it as evidence for life. Should a positive response be obtained, a duplicate sample of the same soil would be heated to "sterilize" it. It would then be tested as a control and should it still show activity similar to the first response, that was evidence that the activity was chemical in nature. However, a nil, or greatly diminished response, was evidence for biology. This same control was to be used for any of the three life detection experiments that showed a positive initial result. The initial assessment of results from the Viking 1 PR experiment was that "analysis of the results shows that a small but significant formation of organic matter occurred" and that the sterilized control showed no evidence of organics, showing that the "findings could be attributed to biological activity." However, given the persistence of organic release at 90 °C, the inhibition of organics after injecting water vapor and, especially, the lack of detection of organics in the
Martian soil by the GCMS experiment, the investigators concluded that a nonbiological explanation of the PR results was most likely. However, in subsequent years, as the GCMS results have come increasingly under scrutiny, the pyrolytic release experiment results have again come to be viewed as possibly consistent with biological activity, although "An explanation for the apparent small synthesis of organic matter in the pyrolytic release experiment remains obscure."
291:
immediately following the first injection. The experiment was done by both Viking probes, the first using a sample from the surface exposed to sunlight and the second probe taking the sample from underneath a rock; both initial injections came back positive. Sterilization control tests were subsequently carried out by heating various soil samples. Samples heated for 3 hours at 160 °C gave off no radioactive gas when nutrients were injected, and samples heated for 3 hours at 50 °C exhibited a substantial reduction in radioactive gas released following nutrient injection. A sample stored at 10 °C for several months was later tested showing significantly reduced radioactive gas release.
312:). When mixed with small organic molecules, superoxidizers readily oxidize them to carbon dioxide, which may account for the LR result. Superoxide chemistry can also account for the puzzling results seen when more nutrients were added to the soil in the LR experiment; because life multiplies, the amount of gas should have increased when a second or third batch of nutrients was added, but if the effect was due to a chemical being consumed in the first reaction, no new gas would be expected. Lastly, many superoxides are relatively unstable and are destroyed at elevated temperatures, also accounting for the "sterilization" seen in the LR experiment."
539:
scientist Rafael
Navarro demonstrated that the Viking biological experiments likely lacked sensitivity to detect trace amounts of organic compounds. In a paper published in December 2010, the scientists suggest that if organics were present, they would not have been detected because when the soil is heated to check for organics, perchlorate destroys them rapidly producing chloromethane and dichloromethane, which is what the Viking landers found. This team also notes that this is not a proof of life but it could make a difference in how scientists look for organic
498:
peroxide nor superoxide is required to explain the results of the Viking biology experiments. A more detailed study was conducted in 2017 by a team of researchers including Quinn. While this study was not specifically designed to match the data from the LR experiment, it was found that hypochlorite could partially explain the control results, including the 160 °C sterilization test. The authors stated "Further experiments are planned to characterize the thermal stability of hypochlorite and other oxychlorine species in the context of the LR experiments."
93:
304:
second and third nutrient injections did not produce any further release of labeled gas." The 2011 edition of the same textbook noted that "Albet Yen of the Jet
Propulsion Laboratory has shown that, under extremely cold and dry conditions and in a carbon dioxide atmosphere, ultraviolet light (remember: Mars lacks an ozone layer, so the surface is bathed in ultraviolet) can cause carbon dioxide to react with soils to produce various oxidizers, including highly reactive
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31:
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the positive LR results are diagnostic for life on Mars. He and others have conducted ongoing experiments attempting to reproduce the Viking data, either with biological or non-biological materials on Earth. While no experiment has ever precisely duplicated the Mars LR test and control results, experiments with
569:
According to
Gilbert Levin and Patricia Ann Straat, investigators of the LR experiment, no explanation involving inorganic chemistry as of 2016 is able to give satisfactory explanations of the complete data from the LR experiment, and specifically address the question of what active agent on the soil
303:
textbook noted that "With unsterilized
Terrestrial samples, though, the addition of more nutrients after the initial incubation would then produce still more radioactive gas as the dormant bacteria sprang into action to consume the new dose of food. This was not true of the Martian soil; on Mars, the
581:
argued that the Viking mission would have done better to examine the
Martian atmosphere than look at the soil. He theorised that all life tends to expel waste gases into the atmosphere, and as such it would be possible to theorise the existence of life on a planet by detecting an atmosphere that was
205:
found by Viking were interpreted as contaminants from Earth was that the ratio of two isotopes of chlorine in them matched the three-to-one ratio for those isotopes on Earth. The ratio for them on Mars has not been clearly determined yet. If it is found to be much different than Earth's, that would
526:
It has also been argued that the
Labeled Release (LR) experiment detected so few metabolising organisms in the Martian soil, that it would have been impossible for the gas chromatograph to detect them. This view has been put forward by the designer of the LR experiment, Gilbert Levin, who believes
401:
on earth do. After several days of incubation, the experiment removed the gases, baked the remaining soil at 650 °C (1200 °F), and collected the products in a device which counted radioactivity. If any of the C had been converted to biomass, it would be vaporized during heating and the
410:
Organic compounds seem to be common, for example, on asteroids, meteorites, comets and the icy bodies orbiting the Sun, so detecting no trace of any organic compound on the surface of Mars came as a surprise. The GC-MS was definitely working, because the controls were effective and it was able to
257:
In early
November 1976, it was reported that "on Viking 2, the gas exchange experiment is producing analogous results to those from Viking 1. Again, oxygen disappeared once the nutrient solution came into contact with the soil. Again, carbon dioxide began to appear and still continues to evolve".
173:
as "while perchlorate is too poor an oxidizer to reproduce the LR results (under the conditions of that experiment perchlorate does not oxidize organics), it does oxidize, and thus destroy, organics at the higher temperatures used in the Viking GCMS experiment. NASA astrobiologist Chris McKay has
538:
While the majority of astrobiologists still conclude that the Viking biological experiments were inconclusive or negative, Gilbert Levin is not alone in believing otherwise. The current claim for life on Mars is grounded on old evidence reinterpreted in the light of recent developments. In 2006,
497:
In 2013, astrobiologist
Richard Quinn at the Ames Center conducted experiments in which amino acids reacting with hypochlorite, which is created when perchlorate is irradiated with gamma rays, seemed to reproduce the findings of the labeled-release experiment. He concluded that neither hydrogen
423:
Despite the positive result from the
Labeled Release experiment, a general assessment is that the results seen in the four experiments are best explained by oxidative chemical reactions with the Martian soil. One of the current conclusions is that the Martian soil, being continuously exposed to
462:
missions from 1965 to 1976. Horowitz considered that the great versatility of the carbon atom makes it the element most likely to provide solutions, even exotic solutions, to the problems of survival of life on other planets. However, he also considered that the conditions found on Mars were
594:, launched in March 2016, implements this approach and will focus on detection, characterization of spatial and temporal variation, and localization of sources for a broad suite of atmospheric trace gases on Mars and help determine if their formation is of biological or geological origin. The
290:
one or more of the nutrients. Such a result was to be followed with the control part of the experiment as described for the PR below. The result was quite a surprise, considering the negative results of the first two tests, with a steady stream of radioactive gases being given off by the soil
201:, "those chemicals are exactly what new study found when a little perchlorate -- the surprise finding from Phoenix -- was added to desert soil from Chile containing organics and analyzed in the manner of the Viking tests." However, the 2010 NASA press release also noted that: "One reason the
493:
as byproduct, the identical chlorine compounds discovered by both Viking landers when they performed the same tests on Mars. Because perchlorate would have broken down any Martian organics, the question of whether Viking found organic compounds is still wide open, as alternative chemical and
598:
has also been attempting – since late 2014 – to detect and map methane on Mars' atmosphere. A press commentary argued that, if there was life at the Viking lander sites, it may have been killed by the exhaust from the landing rockets. That is not a problem for missions which land via an
477:, a strong oxidizer when heated above 200 °C. This was initially thought to be the cause of a false positive LR result. However, results of experiments published in December 2010 propose that organic compounds "could have been present" in the soil analyzed by both
411:
detect traces of chlorine, attributed to the cleaning solvents that had been used to sterilize it prior to launch. A reanalysis of the GC-MS data was performed in 2018, suggesting that organic compounds may actually have been detected, corroborating with data from the
178:-like levels of perchlorates were present in the Viking samples, the organic content of the Martian soil could have been as high as 0.1% and still would have produced the (false) negative result that the GCMS returned. Thus, while conventional wisdom regarding the
206:
support the 1970s interpretation." Biemann has written a commentary critical of the Navarro-González and McKay paper, to which the latter have replied; the exchange was published in December 2011. In 2021 the chlorine isotope ratio on Mars was measured by the
566:' and therefore representative of a new form of life. The taxonomy proposed by Crocco has not been accepted by the scientific community, and the validity of Crocco's interpretation hinged entirely on the absence of an oxidative agent in the Martian soil.
230:. It applied a liquid complex of organic and inorganic nutrients and supplements to a soil sample, first with just nutrients added, then with water added too. Periodically, the instrument sampled the atmosphere of the incubation chamber and used a
136:, MIT) was used to analyze the components of untreated Martian soil, and particularly those components that are released as the soil is heated to different temperatures. It could measure molecules present at a level of a few parts per billion.
510:
on Mars in 2008, some theories remained opposed to the general scientific conclusion. An investigator suggested that the biological explanation of the lack of detected organics by GC-MS could be that the oxidizing inventory of the
419:
involving organic compounds were what those experiments were designed to detect. The general scientific community surmises that the Viking's biological tests remain inconclusive, and can be explained by purely chemical processes.
298:
article from 2000 noted that "Though most of his peers concluded otherwise, Levin still holds that the robot tests he coordinated on the 1976 Viking lander indicated the presence of living organisms on Mars." A 2006
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One speculation is that the function represents metabolism during a period of slow growth or cell division to an asymptotic level of cellular confluence, perhaps similar to terrestrial biofilms in the steady
2888:
Biemann K, Oro J, Toulmin P, Orgel LE, Nier AO, Anderson DM, et al. (October 1976). "Search for organic and volatile inorganic compounds in two surface samples from the chryse planitia region of Mars".
2664:
1348:
5361:
485:, since NASA's Phoenix lander in 2008 detected perchlorate, which can break down organic compounds. The study's authors found that perchlorate can destroy organics when heated and produce
1698:"Identification of Chlorobenzene in the Viking Gas Chromatograph-Mass Spectrometer Data Sets: Reanalysis of Viking Mission Data Consistent With Aromatic Organic Compounds on Mars"
4584:
3145:
1451:
3111:
1007:
Navarro-González R, McKay CP (2011). "Reply to comment by Biemann and Bada on "Reanalysis of the Viking results suggests perchlorate and organics at midlatitudes on Mars"".
147:. This result was difficult to explain if Martian bacterial metabolism was responsible for the positive results seen by the Labeled Release experiment (see below). A 2011
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not in chemical equilibrium. He concluded that there was enough information about Mars' atmosphere at that time to discount the possibility of life there. Since then,
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100:
The four experiments below are presented in the order in which they were carried out by the two Viking landers. The biology team leader for the Viking program was
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Schuerger, Andrew; Clark, Benton (March 2008). "Viking Biology Experiments: Lessons Learned and the Role of Ecology in Future Mars Life-Detection Experiments".
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In a 2002 paper published by Joseph Miller, he speculates that recorded delays in the system's chemical reactions point to biological activity similar to the
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Trokhimovskiy, A.; Fedorova, A.A.; Olsen, K.S.; Alday, J.; Korablev, O.; Montmessin, F.; Lefèvre, F.; Patrakeev, A.; Belyaev, D.; Shakun, A.V. (July 2021).
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at its location in levels exceeding 1.3ppb. later in 2013 and in 2014, measurements by Curiosity did detect methane, suggesting a time-variable source. The
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samples could be adversely affected by heating to approximately 50 °C and destroyed with long-term storage in the dark at 10 °C, as data suggest.
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278:. In the LR experiment, a sample of Martian soil was inoculated with a drop of very dilute aqueous nutrient solution. The nutrients (7 molecules that were
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Guzman, Melissa; McKay, Christopher P.; Quinn, Richard C.; Szopa, Cyril; Davila, Alfonso F.; Navarro-González, Rafael; Freissinet, Caroline (July 2018).
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1541:
Klein HP, Horowitz NH, Levin GV, Oyama VI, Lederberg J, Rich A, et al. (October 1976). "The viking biological investigation: preliminary results".
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2672:
2314:"The limitations on organic detection in Mars-like soils by thermal volatilization-gas chromatography-MS and their implications for the Viking results"
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Brown FS, Adelson HE, Chapman MC, Clausen OW, Cole AJ, Cragin JT, et al. (February 1978). "The biology instrument for the Viking Mars mission".
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436:. A sufficiently strong oxidizing molecule would react with the added water to produce oxygen and hydrogen, and with the nutrients to produce
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193:-- chlorine compounds interpreted at the time as likely contaminants from cleaning fluids." According to a paper authored by a team led by
185:
According to a 2010 NASA press release: "The only organic chemicals identified when the Viking landers heated samples of Martian soil were
2538:
968:"Comment on "Reanalysis of the Viking results suggests perchlorate and organics at midlatitudes on Mars" by Rafael Navarro-González et al"
182:
biology experiments still points to "no evidence of life", recent years have seen at least a small shift toward "inconclusive evidence"."
3094:
1923:
Navarro-González R (2011). "Correction to "Reanalysis of the Viking results suggests perchlorate and organics at midlatitudes on Mars"".
4851:
3934:
3909:
3656:
1980:
1758:
Beegle LW, Wilson MG, Abilleira F, Jordan JF, Wilson GR (August 2007). "A concept for NASA's Mars 2016 astrobiology field laboratory".
603:-protected capsule, slowed by parachutes and retrorockets, and dropped from a height that allows rocket exhaust to avoid the surface.
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4856:
4781:
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254:. The scientists hypothesized that metabolizing organisms would either consume or release at least one of the gases being measured.
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textbook notes that this was the decisive factor due to which "For most of the Viking scientists, the final conclusion was that the
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and found to be almost indistinguishable from the terrestrial ratio, leaving the interpretation of the GCMS results inconclusive.
623:, and the end products of the plume (water, nitrogen, and ammonia) were not found to have affected the soils at the landing site.
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rover. At the time, the total absence of organic material on the surface made the results of the biology experiments moot, since
226:, NASA Ames) looked for gases given off by an incubated soil sample by first replacing the Martian atmosphere with the inert gas
169:
in Martian soil. The 2011 astrobiology textbook discusses the importance of this finding with respect to the results obtained by
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of each chemical. As a result, it can separate, identify, and quantify a large number of different chemicals. The GCMS (PI:
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in the Martian soil. In fact, Martian soils were found to contain less carbon than lifeless lunar soils returned by the
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Klein HP, Lederberg J, Rich A, Horowitz NH, Oyama VI, Levin GV (1976). "The Viking Mission Search For Life On Mars".
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4635:
4194:
4116:
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Quinn R, Zent A (1999). "Peroxide-Modified Titanium Dioxide: a Chemical Analog of Putative Martian Soil Oxidants".
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products) were tagged with radioactive C. The air above the soil was monitored for the evolution of radioactive CO
194:
73:. The landers each used a robotic arm to pick up and place soil samples into sealed test containers on the craft.
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4756:
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Horowitz NH, Hobby GL, Hubbard JS (December 1976). "The viking carbon assimilation experiments: interim report".
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paper suggesting the detection of "extant microbial life on Mars", based on mathematical speculation through
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Navarro-González R, Navarro KF, de la Rosa J, Iñiguez E, Molina P, Miranda LD, et al. (October 2006).
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3899:
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Schulze-Makuch D, Houtkooper JM (2007-05-22). "A Possible Biogenic Origin for Hydrogen Peroxide on Mars".
612:
140:
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Georgiou, Christos D.; Zisimopoulos, Dimitrios; Kalaitzopoulou, Electra; Quinn, Richard C. (April 2017).
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2060:"Radiation-Driven Formation of Reactive Oxygen Species in Oxychlorine-Containing Mars Surface Analogues"
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17:
2464:"The Case for Extant Life on Mars and Its Possible Detection by the Viking Labeled Release Experiment"
1108:"The Case for Extant Life on Mars and Its Possible Detection by the Viking Labeled Release Experiment"
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Miller JD, Straat PA, Levin GV (February 2002). Hoover RB, Levin GV, Paepe RR, Rozanov AY (eds.).
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1955:"Did Viking Mars Landers Find Life's Building Blocks? Missing Piece Inspires New Look at Puzzle"
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1884:"Reanalysis of the Viking results suggests perchlorate and organics at midlatitudes on Mars"
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2936:"On the ability of the Viking gas chromatograph-mass spectrometer to detect organic matter"
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3095:"The Viking Mission Labeled Release Experiment and the Search for Martian Life: Part I"
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Mukhopadhyay R (October 2007). "The Viking GC/MS and the search for organics on Mars".
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2002:
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Quinn RC, Martucci HF, Miller SR, Bryson CE, Grunthaner FJ, Grunthaner PJ (June 2013).
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O solvent well exceeded the reducing power of the organic compounds of the organisms.
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organisms present, it was believed that they would incorporate some of the carbon as
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Proceedings of the National Academy of Sciences of the United States of America
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Proceedings of the National Academy of Sciences of the United States of America
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3165:. Coloring of the base map indicates relative elevations of Martian surface.
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3112:"The first in situ search for extraterrestrial life: Viking Mission to Mars"
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Navarro-Gonzáles R, Vargas E, de la Rosa J, Raga AC, McKay CP (2010-12-15).
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lander descended to the surface with retro-rockets, however, their fuel was
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286:(or other carbon-based) gas as evidence that microorganisms in the soil had
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The two landers carried out the same tests at two places on Mars' surface,
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Klein HP (1992). "The Viking biology experiments: Epilogue and prologue".
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2003:"Perchlorate radiolysis on Mars and the origin of martian soil reactivity"
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4271:
4183:
4176:
4071:
4002:
3603:
3596:
3536:
3531:
3518:
3511:
3225:
3220:
2753:
2174:
1940:
1908:
1883:
1721:
1266:
1028:
992:
967:
762:
Acevedo S (2001-12-01). "In Memoriam Dr. Harold P. Klein (1921 - 2001)".
677:
670:
358:, Caltech) consisted of the use of light, water, and a carbon-containing
247:
243:
61:
55:
3641:
3169:
2567:
Webster CR, Mahaffy PR, Atreya SK, Flesch GJ, Farley KA (October 2013).
2126:
1635:
Klein, Harold (June 1978). "The Viking biological experiments on Mars".
5160:
4986:
4081:
4056:
3760:
3281:
3276:
2864:
1258:
649:
548:
433:
390:
382:
251:
3548:
3034:
2745:
1536:
1534:
1532:
1372:
5403:
4976:
4946:
4936:
4896:
4564:
4076:
3984:
3331:
3326:
3315:
3310:
3299:
3294:
2782:
2698:
600:
374:), simulating that on Mars. The carbon-bearing gases were made with
235:
227:
2409:"Life's Building Blocks May Have Been Found on Mars, Research Finds"
1349:"Periodic analysis of the Viking lander Labeled Release experiment"
5319:
5191:
3134:
3082:"Viking Biology from the NASA NSSDC Master Catalog of Experiments"
2278:
91:
5266:
3846:
50:
4624:
4620:
3645:
3552:
1411:"Complexity Analysis of the Viking Labeled Release Experiments"
120:) is a device that separates vapor components chemically via a
2190:"I'm Convinced We Found Evidence of Life on Mars in the 1970s"
295:
1297:"Mars sample return plan carries microbial risk, group warns"
1235:"Completion of the Viking labeled release experiment on Mars"
3088:. U.S. National Aeronautics and Space Administration (NASA).
3075:. U.S. National Aeronautics and Space Administration (NASA).
3052:"Martian Life Could Have Evaded Detection by Viking Landers"
2665:"NASA orbiter to hunt for source of Martian methane in 2016"
1173:"Viking Labeled Release Biology Experiment: Interim Results"
822:
Kieffer HH, Jakosky BM, Snyder CW, Matthews M (1992-10-01).
586:' atmosphere at 10ppb, thus reopening this debate. Although
326:
On 12 April 2012, an international team including Levin and
1823:
Utopia and Back and the search for life in the solar system
1409:
Bianciardi G, Miller JD, Straat PA, Levin GV (March 2012).
686:(The next NASA mission with primary science life detection)
34:
Schematic of the Viking Lander Biological Experiment System
2373:"The Red Soil on Mars as a proof for water and vegetation"
234:
to measure the concentrations of several gases, including
5362:
Astrobiology Science and Technology for Exploring Planets
1044:"Isotopes of chlorine from HCl in the Martian atmosphere"
2307:
2305:
1233:
Levin, Gilbert V.; Straat, Patricia Ann (1 March 1979).
1106:
Levin, Gilbert V.; Straat, Patricia Ann (October 2016).
3016:. National Aeronautics and Space Administration (NASA).
937:
Webster G, Hoover R, Marlaire R, Frias G (2010-09-03).
2798:
Klein HP (1999). "Did Viking Discover Life on Mars?".
2520:"The Viking Lander Labeled Release Experiment Archive"
1353:
Instruments, Methods, and Missions for Astrobiology IV
4585:
Potential cultural impact of extraterrestrial contact
2264:
Levin G (2007). "Analysis of evidence of Mars life".
1171:
Levin, Gilbert; Straat, Patricia (17 December 1976).
155:
missions failed to detect life in the Martian soil."
2438:"Science works through Mars lander life controversy"
615:
each used this landing technique successfully. The
588:
in 2013 the Curiosity rover failed to detect methane
5347:
5280:
5179:
5141:
5125:
5093:
5010:
4919:
4910:
4820:
4724:
4658:
4505:
4441:
4380:
4335:
4193:
3993:
3898:
3862:
3815:
3772:
3745:
3738:
3679:
3618:
3586:
2845:
Journal Origins of Life and Evolution of Biospheres
2800:
Journal Origins of Life and Evolution of Biospheres
2215:
Journal Origins of Life and Evolution of Biospheres
896:
894:
2695:"Did probes find Martian life ... or kill it off?"
2440:. Contactincontext.org. 2007-03-22. Archived from
1315:
823:
4882:Habitability of F-type main-sequence star systems
4872:Habitability of K-type main-sequence star systems
3965:Habitability of F-type main-sequence star systems
3955:Habitability of K-type main-sequence star systems
3014:On Mars: Exploration of the Red Planet. 1958-1978
4252:Communication with extraterrestrial intelligence
1480:
1478:
941:. NASA Jet Propulsion Laboratory. Archived from
939:"Missing Piece Inspires New Look at Mars Puzzle"
4807:Search for extraterrestrial intelligence (SETI)
3176:Clicking on the labels will open a new article.
2697:. Associated Press via NBC News. Archived from
558:went as far as proposing the creation of a new
2569:"Low upper limit to methane abundance on Mars"
1452:"Life on Mars Found by NASA's Viking Mission?"
961:
959:
764:Origins of Life and Evolution of the Biosphere
432:), has built up a thin layer of a very strong
274:, Biospherics Inc.) gave the most promise for
4636:
3657:
3564:
1996:
1994:
1877:
1875:
1674:. Malin Space Science Systems. Archived from
877:(2nd ed.). JHU Press. pp. 282–283.
8:
4787:List of microorganisms tested in outer space
3073:"The Viking Lander Labeled Release Data Set"
4560:History of the extraterrestrial life debate
4257:Gauss's Pythagorean right triangle proposal
3101:. Colorado State University. Archived from
2987:DiGregorio BE, Levin GV, Straat PA (1997).
139:The GCMS measured no significant amount of
65:, then carried out experiments to look for
5212:Enceladus Life Signatures and Habitability
4916:
4643:
4629:
4621:
3875:Planetary habitability in the Solar System
3742:
3664:
3650:
3642:
3571:
3557:
3549:
709:
707:
705:
703:
701:
551:program may help settle this controversy.
338:of the Labeled Release experiments of the
5399:European Astrobiology Network Association
2969:
2959:
2495:
2402:
2400:
2347:
2337:
2277:
2125:
2034:
1907:
1434:
1147:
1067:
991:
932:
930:
806:"Harold P. Klein, NASA Ames Hall of Fame"
494:biological interpretations are possible.
4892:List of potentially habitable exoplanets
4302:Search for extraterrestrial intelligence
3970:List of potentially habitable exoplanets
1981:"Would We Know Alien Life If We Saw It?"
1888:Journal of Geophysical Research: Planets
1702:Journal of Geophysical Research: Planets
562:that classified some Viking results as '
543:in the future. Results from the current
199:National Autonomous University of Mexico
29:
18:Viking spacecraft biological experiments
5310:Living Interplanetary Flight Experiment
4107:Living Interplanetary Flight Experiment
2628:, Dec. 16, 2014 (accessed 25 Oct. 2016)
2626:Curiosity Detects Methane Spike on Mars
697:
2993:. Berkeley, CA: North Atlantic Books.
2539:"James Lovelock, Gaia's grand old man"
1825:. New York: W.H. Freeman and Company.
853:
843:
5300:Biological Oxidant and Life Detection
4008:Biological Oxidant and Life Detection
2114:International Journal of Astrobiology
639:Biological Oxidant and Life Detection
506:Before the discovery of the oxidizer
463:incompatible with carbon based life.
428:from the Sun (Mars has no protective
158:Experiments conducted in 2008 by the
114:gas chromatograph — mass spectrometer
108:Gas chromatograph — mass spectrometer
53:. The first successful Mars landers,
7:
5449:
4877:Habitability of yellow dwarf systems
4862:Habitability of neutron star systems
3960:Habitability of yellow dwarf systems
3945:Habitability of neutron star systems
3705:Viking lander biological experiments
3610:Viking lander biological experiments
2726:The Review of Scientific Instruments
2462:Levin GV, Straat PA (October 2016).
4852:Habitability of binary star systems
3935:Habitability of binary star systems
3910:Catalog of Nearby Habitable Systems
1844:"Perchlorate found in Martian soil"
584:methane has been discovered in Mars
319:previously observed in terrestrial
42:landers each carried four types of
5414:Nexus for Exoplanet System Science
4857:Habitability of natural satellites
4782:Hypothetical types of biochemistry
4570:Nexus for Exoplanet System Science
4413:Hypothetical types of biochemistry
3940:Habitability of natural satellites
3086:National Space Science Data Center
2640:"Agencies outline Mars initiative"
1318:Astrobiology: A Brief Introduction
904:Astrobiology: A Brief Introduction
874:Astrobiology: A Brief Introduction
547:mission and the under-development
25:
5394:Center for Life Detection Science
5315:Mars Astrobiology Explorer-Cacher
4867:Habitability of red dwarf systems
3950:Habitability of red dwarf systems
901:Plaxco KW, Gross M (2011-08-12).
124:and then feeds the result into a
5448:
5437:
5436:
5419:Ocean Worlds Exploration Program
5252:Life Investigation For Enceladus
4772:Extraterrestrial sample curation
4102:Life Investigation For Enceladus
3530:
3510:
3492:
3472:
3454:
3433:
3415:
3397:
3377:
3359:
3341:
3325:
3309:
3293:
3275:
3257:
3237:
3219:
3168:
3157:, overlaid with the position of
2194:Scientific American Blog Network
2188:Levin, Gilbert V. (2019-10-10).
717:Life on Mars; The Complete Story
5357:Astrobiology Society of Britain
5232:Explorer of Enceladus and Titan
4887:Habitable zone for complex life
1925:Journal of Geophysical Research
1009:Journal of Geophysical Research
972:Journal of Geophysical Research
907:. JHU Press. pp. 285–286.
830:. University of Arizona Press.
535:have produced similar results.
27:Mars life detection experiments
5242:Journey to Enceladus and Titan
4092:Journey to Enceladus and Titan
2380:Geophysical Research Abstracts
1927:. Vol. 116, no. E8.
1239:Journal of Molecular Evolution
1:
5290:Astrobiology Field Laboratory
4842:Extraterrestrial liquid water
4225:Berkeley SETI Research Center
3925:Extraterrestrial liquid water
1862:"Martian Life Or Not? NASA's
1507:10.1126/science.194.4271.1321
1197:10.1126/science.194.4271.1322
5424:Spanish Astrobiology Center‎
4832:Circumstellar habitable zone
4545:Extraterrestrials in fiction
4418:Interplanetary contamination
3915:Circumstellar habitable zone
3799:(unusual light fluctuations)
3791:(unusual light fluctuations)
3783:(unusual light fluctuations)
3110:Whitaker N (December 2009).
2671:. 2009-03-06. Archived from
1868:. Science Daily. 2008-08-06.
1657:10.1016/0019-1035(78)90053-2
1095:. Reed Business Information.
1091:Burgess, Eric (1976-11-04).
1048:Astronomy & Astrophysics
174:estimated, in fact, that if
5477:Astrobiology space missions
5409:NASA Astrobiology Institute
4403:Extraterrestrial hypothesis
3008:Ezell LN, Ezell EC (1984).
2911:10.1126/science.194.4260.72
2693:Borenstein S (2007-01-07).
1563:10.1126/science.194.4260.99
1314:Plaxco KW, Gross M (2006).
1069:10.1051/0004-6361/202140916
966:Biemann K, Bada JL (2011).
871:Plaxco KW, Gross M (2011).
454:bioscience section for the
165:discovered the presence of
5503:
5257:Mars sample return mission
4117:Mars sample-return mission
3050:Than K (23 October 2006).
1670:Caplinger M (April 1995).
1436:10.5139/IJASS.2012.13.1.14
385:of carbon. If there were
5432:
5335:Terrestrial Planet Finder
4757:Earliest known life forms
3870:Earliest known life forms
3631:Jet Propulsion Laboratory
3155:global topography of Mars
3093:Smith R (12 March 2004).
2144:10.1017/S1473550407003746
1614:10.1007/s11214-007-9194-2
592:ExoMars Trace Gas Orbiter
452:Jet Propulsion Laboratory
5367:Breakthrough Initiatives
4235:Breakthrough Initiatives
2537:Joseph LE (2000-08-17).
1985:Air & Space Magazine
1842:Johnson J (2008-08-06).
1295:Stenger R (2000-11-07).
5028:Mars Science Laboratory
4847:Galactic habitable zone
4339:extraterrestrial beings
3930:Galactic habitable zone
2990:Mars: The Living Planet
2961:10.1073/pnas.0703732104
2934:Biemann K (June 2007).
2820:10.1023/A:1006514327249
2638:Rincon P (2009-07-09).
2596:10.1126/science.1242902
2339:10.1073/pnas.0604210103
2235:10.1023/A:1006506022182
1821:Horowitz, N.H. (1986).
1060:2021A&A...651A..32T
784:10.1023/A:1013387122386
613:Mars Exploration Rovers
545:Mars Science Laboratory
393:through the process of
350:The pyrolytic release (
195:Rafael Navarro-González
5207:Enceladus Life Finder‎
5187:Breakthrough Enceladus
4711:Planetary oceanography
4487:Planetarium hypothesis
4477:Hart–Tipler conjecture
4462:Dark forest hypothesis
4452:Aestivation hypothesis
4171:Venus In Situ Explorer
3975:Planetary habitability
3764:(misidentified quasar)
3756:(misidentified pulsar)
3216:
1979:Bell TE (April 2016).
1866:Team Analyzes Results"
406:Scientific conclusions
97:
38:In 1976 two identical
35:
5487:Extraterrestrial life
5382:Breakthrough Starshot
4982:Lunar Micro Ecosystem
4902:Superhabitable planet
4767:Extraterrestrial life
4590:Post-detection policy
4492:Rare Earth hypothesis
4317:Voyager Golden Record
4210:Allen Telescope Array
4045:Enceladus Life Finder
3980:Superhabitable planet
3673:Extraterrestrial life
3151:Interactive image map
3138:
3128:on 28 September 2013.
2488:10.1089/ast.2015.1464
2407:Wall M (2011-01-06).
2084:10.1089/ast.2016.1539
2027:10.1089/ast.2013.0999
1780:10.1089/ast.2007.0153
1594:Space Science Reviews
1450:Than K (2012-04-13).
1322:. JHU Press. p.
1132:10.1089/ast.2015.1464
720:. London: Blandford.
450:was the chief of the
397:, just as plants and
266:The labeled release (
128:, which measures the
95:
80:near the equator and
33:
5389:Carl Sagan Institute
5377:Breakthrough Message
5217:Enceladus Orbilander
4952:Biosatellite program
4802:Planetary protection
4686:Evolutionary biology
4676:Atmospheric sciences
4580:Planetary protection
4467:Firstborn hypothesis
4457:Berserker hypothesis
4428:Mediocrity principle
4245:Breakthrough Message
3863:Life in the Universe
3023:Analytical Chemistry
2266:ElectroneurobiologĂa
2175:10.1117/2.3201403.03
1941:10.1029/2011JE003854
1909:10.1029/2010JE003599
1722:10.1029/2018JE005544
1029:10.1029/2011JE003880
993:10.1029/2011JE003869
684:Europa Lander (NASA)
596:Mars Orbiter Mission
466:In August 2008, the
203:chlorinated organics
5372:Breakthrough Listen
4393:Directed panspermia
4372:Reptilian humanoids
4240:Breakthrough Listen
4220:Arecibo Observatory
4166:Titan Mare Explorer
3739:Signals of interest
3699:Murchison meteorite
3687:Shergotty meteorite
3626:Exploration of Mars
3580:Viking Mars landers
3352:Mars Polar Lander ↓
3211:Mars Memorials list
3119:SCLH Astronomy Club
2952:2007PNAS..10410310B
2903:1976Sci...194...72B
2857:1992OLEB...21..255K
2812:1999OLEB...29..625K
2775:1976Natur.262...24K
2738:1978RScI...49..139B
2701:on December 5, 2013
2588:2013Sci...342..355W
2480:2016AsBio..16..798L
2330:2006PNAS..10316089N
2288:2007arXiv0705.3176L
2227:1999OLEB...29...59Q
2136:2007IJAsB...6..147H
2076:2017AsBio..17..319G
2019:2013AsBio..13..515Q
1933:2011JGRE..116.8011N
1900:2010JGRE..11512010N
1772:2007AsBio...7..545B
1714:2018JGRE..123.1674G
1649:1978Icar...34..666K
1606:2008SSRv..135..233S
1555:1976Sci...194...99K
1499:1976Sci...194.1321H
1457:National Geographic
1427:2012IJASS..13...14B
1365:2002SPIE.4495...96M
1251:1979JMolE..14..167L
1189:1976Sci...194.1322L
1183:(4271): 1322–1329.
1124:2016AsBio..16..798L
1021:2011JGRE..11612002N
984:2011JGRE..11612001B
776:2001OLEB...31..549A
714:Chambers P (1999).
655:Exploration of Mars
340:1976 Viking Mission
328:Patricia Ann Straat
308:(salts containing O
5202:Enceladus Explorer
4515:Ancient astronauts
4112:Mars Geyser Hopper
4040:Enceladus Explorer
3680:Events and objects
3217:
3010:"Life or No Life?"
2865:10.1007/BF01809861
1894:(E12010): E12010.
1259:10.1007/BF01732376
560:nomenclatural rank
354:) experiment (PI:
270:) experiment (PI:
222:) experiment (PI:
218:The gas exchange (
98:
49:to the surface of
36:
5464:
5463:
5343:
5342:
5167:Rosalind Franklin
5080:Trace Gas Orbiter
4737:Allan Hills 84001
4716:Planetary science
4618:
4617:
4148:SpaceX Red Dragon
4063:Rosalind Franklin
3858:
3857:
3717:Allan Hills 84001
3711:Allan Hills 77005
3639:
3638:
3542:
3524:
3504:
3486:
3466:
3448:
3427:
3425:Rosalind Franklin
3409:
3391:
3371:
3353:
3335:
3319:
3303:
3287:
3269:
3251:
3231:
3174:Clickable image:
3035:10.1021/ac071972t
3000:978-1-883319-58-8
2746:10.1063/1.1135378
1848:Los Angeles Times
1464:on April 15, 2012
1373:10.1117/12.454748
1333:978-0-8018-8366-8
914:978-1-4214-0194-2
884:978-1-4214-0194-2
837:978-0-8165-1257-7
727:978-0-7137-2747-0
529:hydrogen peroxide
346:Pyrolytic release
232:gas chromatograph
208:Trace Gas Orbiter
141:organic molecules
126:mass spectrometer
122:gas chromatograph
16:(Redirected from
5494:
5452:
5451:
5440:
5439:
4917:
4812:Yamato meteorite
4645:
4638:
4631:
4622:
4595:San Marino Scale
4535:Brookings Report
4482:Neocatastrophism
4388:Cosmic pluralism
4362:Little green men
4337:Types of alleged
4262:Astrolinguistics
3851:
3843:
3842:(unknown origin)
3839:Fast radio burst
3835:
3827:
3808:
3807:(unknown origin)
3804:HD 164595 signal
3800:
3792:
3784:
3765:
3757:
3743:
3693:Nakhla meteorite
3666:
3659:
3652:
3643:
3573:
3566:
3559:
3550:
3545:
3543:
3538:
3534:
3527:
3525:
3520:
3514:
3507:
3505:
3500:
3496:
3489:
3487:
3482:
3476:
3469:
3467:
3462:
3458:
3451:
3449:
3443:
3437:
3430:
3428:
3423:
3419:
3412:
3410:
3405:
3401:
3394:
3392:
3387:
3381:
3374:
3372:
3367:
3363:
3356:
3354:
3351:
3345:
3338:
3336:
3333:
3329:
3322:
3320:
3317:
3313:
3306:
3304:
3301:
3297:
3290:
3288:
3283:
3279:
3272:
3270:
3267:
3261:
3254:
3252:
3247:
3241:
3234:
3232:
3227:
3223:
3214:
3201:
3200:
3198:
3193:
3191:
3186:
3184:
3172:
3137:
3129:
3127:
3121:. Archived from
3116:
3106:
3105:on 2 April 2009.
3089:
3076:
3059:
3046:
3017:
3004:
2983:
2973:
2963:
2930:
2884:
2851:(4): 1573–0875.
2839:
2806:(6): 1573–0875.
2794:
2783:10.1038/262024a0
2757:
2710:
2709:
2707:
2706:
2690:
2684:
2683:
2681:
2680:
2661:
2655:
2654:
2652:
2651:
2635:
2629:
2622:
2616:
2615:
2573:
2564:
2558:
2557:
2555:
2554:
2545:. Archived from
2534:
2528:
2527:
2516:
2510:
2509:
2499:
2459:
2453:
2452:
2450:
2449:
2434:
2428:
2427:
2425:
2424:
2415:. Archived from
2404:
2395:
2394:
2392:
2391:
2377:
2371:Paepe R (2007).
2368:
2362:
2361:
2351:
2341:
2324:(44): 16089–94.
2309:
2300:
2299:
2281:
2261:
2255:
2254:
2210:
2204:
2203:
2201:
2200:
2185:
2179:
2178:
2162:
2156:
2155:
2129:
2109:
2103:
2102:
2100:
2098:
2055:
2049:
2048:
2038:
1998:
1989:
1988:
1976:
1970:
1969:
1967:
1966:
1951:
1945:
1944:
1920:
1914:
1913:
1911:
1879:
1870:
1869:
1858:
1852:
1851:
1839:
1833:
1819:
1813:
1812:
1810:
1809:
1798:
1792:
1791:
1755:
1749:
1748:
1746:
1744:
1708:(7): 1674–1683.
1693:
1687:
1686:
1684:
1683:
1667:
1661:
1660:
1632:
1626:
1625:
1600:(1–4): 233–243.
1589:
1583:
1582:
1549:(4260): 99–105.
1538:
1527:
1526:
1493:(4271): 1321–2.
1482:
1473:
1472:
1470:
1469:
1460:. Archived from
1447:
1441:
1440:
1438:
1406:
1400:
1399:
1393:
1392:
1383:. Archived from
1344:
1338:
1337:
1321:
1311:
1305:
1304:
1292:
1286:
1285:
1283:
1281:
1230:
1224:
1223:
1221:
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1168:
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1161:
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1103:
1097:
1096:
1088:
1082:
1081:
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1032:
1004:
998:
997:
995:
963:
954:
953:
951:
950:
934:
925:
924:
922:
921:
898:
889:
888:
868:
862:
861:
855:
851:
849:
841:
829:
819:
813:
812:
810:
802:
796:
795:
759:
753:
752:
750:
749:
738:
732:
731:
711:
533:titanium dioxide
336:cluster analysis
317:circadian rhythm
130:molecular weight
21:
5502:
5501:
5497:
5496:
5495:
5493:
5492:
5491:
5467:
5466:
5465:
5460:
5428:
5349:
5339:
5282:
5276:
5237:Icebreaker Life
5175:
5137:
5121:
5095:
5089:
5006:
4912:
4906:
4823:
4816:
4720:
4696:Geomicrobiology
4654:
4649:
4619:
4614:
4610:Xenoarchaeology
4600:Technosignature
4501:
4437:
4423:Kardashev scale
4376:
4338:
4331:
4327:Xenolinguistics
4292:Project Phoenix
4282:Project Cyclops
4267:Lincos language
4230:Bracewell probe
4215:Arecibo message
4196:
4189:
4087:Icebreaker Life
3989:
3901:
3894:
3854:
3849:
3841:
3833:
3825:
3811:
3806:
3798:
3790:
3782:
3768:
3763:
3755:
3734:
3675:
3670:
3640:
3635:
3614:
3582:
3577:
3547:
3546:
3537:
3535:
3528:
3519:
3517:
3515:
3508:
3499:
3497:
3490:
3481:
3479:
3477:
3470:
3461:
3459:
3452:
3442:
3440:
3438:
3431:
3422:
3420:
3413:
3404:
3402:
3395:
3386:
3384:
3382:
3375:
3366:
3364:
3357:
3350:
3348:
3346:
3339:
3332:
3330:
3323:
3316:
3314:
3307:
3300:
3298:
3291:
3282:
3280:
3273:
3266:
3264:
3262:
3255:
3246:
3244:
3242:
3235:
3226:
3224:
3215:
3204:
3202:
3196:
3195:
3189:
3188:
3182:
3181:
3180:
3177:
3166:
3149:
3135:
3132:
3125:
3114:
3109:
3099:Semester at Sea
3092:
3079:
3071:
3067:
3062:
3049:
3029:(19): 7249–56.
3020:
3007:
3001:
2986:
2946:(25): 10310–3.
2933:
2887:
2842:
2797:
2769:(5563): 24–27.
2760:
2723:
2719:
2717:Further reading
2714:
2713:
2704:
2702:
2692:
2691:
2687:
2678:
2676:
2663:
2662:
2658:
2649:
2647:
2637:
2636:
2632:
2623:
2619:
2582:(6156): 355–7.
2571:
2566:
2565:
2561:
2552:
2550:
2536:
2535:
2531:
2518:
2517:
2513:
2474:(10): 798–810.
2461:
2460:
2456:
2447:
2445:
2436:
2435:
2431:
2422:
2420:
2406:
2405:
2398:
2389:
2387:
2375:
2370:
2369:
2365:
2311:
2310:
2303:
2263:
2262:
2258:
2212:
2211:
2207:
2198:
2196:
2187:
2186:
2182:
2164:
2163:
2159:
2127:physics/0610093
2111:
2110:
2106:
2096:
2094:
2057:
2056:
2052:
2000:
1999:
1992:
1978:
1977:
1973:
1964:
1962:
1953:
1952:
1948:
1922:
1921:
1917:
1881:
1880:
1873:
1860:
1859:
1855:
1841:
1840:
1836:
1820:
1816:
1807:
1805:
1802:"ExoMars rover"
1800:
1799:
1795:
1757:
1756:
1752:
1742:
1740:
1695:
1694:
1690:
1681:
1679:
1669:
1668:
1664:
1634:
1633:
1629:
1591:
1590:
1586:
1540:
1539:
1530:
1484:
1483:
1476:
1467:
1465:
1449:
1448:
1444:
1408:
1407:
1403:
1390:
1388:
1346:
1345:
1341:
1334:
1313:
1312:
1308:
1294:
1293:
1289:
1279:
1277:
1232:
1231:
1227:
1217:
1215:
1170:
1169:
1165:
1118:(10): 798–810.
1105:
1104:
1100:
1093:"New Scientist"
1090:
1089:
1085:
1041:
1040:
1036:
1015:(E12): E12002.
1006:
1005:
1001:
978:(E12): E12001.
965:
964:
957:
948:
946:
936:
935:
928:
919:
917:
915:
900:
899:
892:
885:
870:
869:
865:
852:
842:
838:
821:
820:
816:
808:
804:
803:
799:
761:
760:
756:
747:
745:
740:
739:
735:
728:
713:
712:
699:
694:
689:
629:
605:Mars Pathfinder
576:
522:
518:
514:
504:
491:dichloromethane
448:Norman Horowitz
443:
408:
395:carbon fixation
378:(C), a heavy,
373:
364:carbon monoxide
356:Norman Horowitz
348:
311:
285:
264:
262:Labeled release
241:
216:
191:dichloromethane
110:
102:Harold P. Klein
90:
88:The experiments
84:further north.
28:
23:
22:
15:
12:
11:
5:
5500:
5498:
5490:
5489:
5484:
5482:Viking program
5479:
5469:
5468:
5462:
5461:
5459:
5458:
5446:
5433:
5430:
5429:
5427:
5426:
5421:
5416:
5411:
5406:
5401:
5396:
5391:
5386:
5385:
5384:
5379:
5374:
5364:
5359:
5353:
5351:
5345:
5344:
5341:
5340:
5338:
5337:
5332:
5327:
5325:Northern Light
5322:
5317:
5312:
5307:
5302:
5297:
5292:
5286:
5284:
5281:Cancelled and
5278:
5277:
5275:
5274:
5269:
5264:
5259:
5254:
5249:
5244:
5239:
5234:
5229:
5224:
5219:
5214:
5209:
5204:
5199:
5194:
5189:
5183:
5181:
5177:
5176:
5174:
5173:
5172:
5171:
5158:
5156:Europa Clipper
5153:
5145:
5143:
5139:
5138:
5136:
5135:
5129:
5127:
5123:
5122:
5120:
5119:
5112:
5107:
5099:
5097:
5091:
5090:
5088:
5087:
5082:
5077:
5076:
5075:
5062:
5055:
5054:
5053:
5040:
5039:
5038:
5025:
5020:
5014:
5012:
5008:
5007:
5005:
5004:
4999:
4994:
4989:
4984:
4979:
4974:
4969:
4964:
4959:
4954:
4949:
4944:
4939:
4934:
4929:
4923:
4921:
4914:
4908:
4907:
4905:
4904:
4899:
4894:
4889:
4884:
4879:
4874:
4869:
4864:
4859:
4854:
4849:
4844:
4839:
4834:
4828:
4826:
4818:
4817:
4815:
4814:
4809:
4804:
4799:
4794:
4789:
4784:
4779:
4774:
4769:
4764:
4759:
4754:
4752:Drake equation
4749:
4744:
4739:
4734:
4728:
4726:
4722:
4721:
4719:
4718:
4713:
4708:
4703:
4698:
4693:
4691:Exoplanetology
4688:
4683:
4678:
4673:
4668:
4666:Astrochemistry
4662:
4660:
4656:
4655:
4650:
4648:
4647:
4640:
4633:
4625:
4616:
4615:
4613:
4612:
4607:
4602:
4597:
4592:
4587:
4582:
4577:
4572:
4567:
4562:
4557:
4552:
4547:
4542:
4537:
4532:
4527:
4522:
4517:
4511:
4509:
4507:Related topics
4503:
4502:
4500:
4499:
4497:Zoo hypothesis
4494:
4489:
4484:
4479:
4474:
4469:
4464:
4459:
4454:
4448:
4446:
4439:
4438:
4436:
4435:
4430:
4425:
4420:
4415:
4410:
4405:
4400:
4398:Drake equation
4395:
4390:
4384:
4382:
4378:
4377:
4375:
4374:
4369:
4364:
4359:
4354:
4349:
4343:
4341:
4333:
4332:
4330:
4329:
4324:
4319:
4314:
4309:
4304:
4299:
4294:
4289:
4284:
4279:
4277:Pioneer plaque
4274:
4269:
4264:
4259:
4254:
4249:
4248:
4247:
4242:
4232:
4227:
4222:
4217:
4212:
4207:
4201:
4199:
4191:
4190:
4188:
4187:
4180:
4173:
4168:
4163:
4158:
4150:
4145:
4137:
4129:
4127:Northern Light
4124:
4119:
4114:
4109:
4104:
4099:
4094:
4089:
4084:
4079:
4074:
4069:
4068:
4067:
4054:
4051:Europa Clipper
4047:
4042:
4037:
4030:
4023:
4015:
4010:
4005:
3999:
3997:
3995:Space missions
3991:
3990:
3988:
3987:
3982:
3977:
3972:
3967:
3962:
3957:
3952:
3947:
3942:
3937:
3932:
3927:
3922:
3917:
3912:
3906:
3904:
3896:
3895:
3893:
3892:
3887:
3882:
3877:
3872:
3866:
3864:
3860:
3859:
3856:
3855:
3853:
3852:
3850:(radio signal)
3844:
3836:
3834:(inconclusive)
3828:
3826:(radio source)
3819:
3817:
3813:
3812:
3810:
3809:
3801:
3793:
3788:EPIC 204278916
3785:
3776:
3774:
3770:
3769:
3767:
3766:
3758:
3749:
3747:
3740:
3736:
3735:
3733:
3732:
3726:
3720:
3714:
3708:
3702:
3696:
3690:
3683:
3681:
3677:
3676:
3671:
3669:
3668:
3661:
3654:
3646:
3637:
3636:
3634:
3633:
3628:
3622:
3620:
3616:
3615:
3613:
3612:
3607:
3600:
3592:
3590:
3588:Viking program
3584:
3583:
3578:
3576:
3575:
3568:
3561:
3553:
3529:
3516:
3509:
3491:
3478:
3471:
3453:
3439:
3432:
3414:
3396:
3383:
3376:
3358:
3347:
3340:
3324:
3308:
3292:
3274:
3263:
3256:
3243:
3236:
3218:
3203:
3199: Planned)
3192: Inactive
3178:
3167:
3159:Martian rovers
3139:
3133:
3131:
3130:
3107:
3090:
3077:
3068:
3066:
3065:External links
3063:
3061:
3060:
3047:
3018:
3005:
2999:
2984:
2931:
2897:(4260): 72–6.
2885:
2840:
2795:
2758:
2720:
2718:
2715:
2712:
2711:
2685:
2669:Thaindian News
2656:
2630:
2617:
2559:
2529:
2511:
2454:
2429:
2396:
2363:
2301:
2256:
2205:
2180:
2157:
2104:
2070:(4): 319–336.
2050:
1990:
1971:
1946:
1915:
1871:
1853:
1834:
1814:
1793:
1750:
1688:
1672:"Life on Mars"
1662:
1627:
1584:
1528:
1474:
1442:
1401:
1339:
1332:
1306:
1287:
1245:(1): 167–183.
1225:
1163:
1098:
1083:
1034:
999:
955:
926:
913:
890:
883:
863:
836:
814:
797:
770:(6): 549–551.
754:
733:
726:
696:
695:
693:
690:
688:
687:
681:
674:
667:
665:Viking program
662:
657:
652:
647:
642:
636:
630:
628:
625:
611:rover and the
579:James Lovelock
575:
572:
520:
516:
512:
503:
500:
441:
438:carbon dioxide
407:
404:
387:photosynthetic
371:
368:carbon dioxide
347:
344:
309:
283:
263:
260:
239:
215:
212:
145:Apollo program
109:
106:
89:
86:
40:Viking program
26:
24:
14:
13:
10:
9:
6:
4:
3:
2:
5499:
5488:
5485:
5483:
5480:
5478:
5475:
5474:
5472:
5457:
5456:
5447:
5445:
5444:
5435:
5434:
5431:
5425:
5422:
5420:
5417:
5415:
5412:
5410:
5407:
5405:
5402:
5400:
5397:
5395:
5392:
5390:
5387:
5383:
5380:
5378:
5375:
5373:
5370:
5369:
5368:
5365:
5363:
5360:
5358:
5355:
5354:
5352:
5346:
5336:
5333:
5331:
5328:
5326:
5323:
5321:
5318:
5316:
5313:
5311:
5308:
5306:
5303:
5301:
5298:
5296:
5293:
5291:
5288:
5287:
5285:
5279:
5273:
5270:
5268:
5265:
5263:
5260:
5258:
5255:
5253:
5250:
5248:
5245:
5243:
5240:
5238:
5235:
5233:
5230:
5228:
5225:
5223:
5222:Europa Lander
5220:
5218:
5215:
5213:
5210:
5208:
5205:
5203:
5200:
5198:
5195:
5193:
5190:
5188:
5185:
5184:
5182:
5178:
5170:
5168:
5164:
5163:
5162:
5159:
5157:
5154:
5152:
5151:
5147:
5146:
5144:
5140:
5134:
5131:
5130:
5128:
5124:
5118:
5117:
5113:
5111:
5108:
5106:
5105:
5101:
5100:
5098:
5092:
5086:
5083:
5081:
5078:
5074:
5072:
5068:
5067:
5066:
5063:
5061:
5060:
5056:
5052:
5050:
5046:
5045:
5044:
5041:
5037:
5035:
5031:
5030:
5029:
5026:
5024:
5021:
5019:
5016:
5015:
5013:
5009:
5003:
5000:
4998:
4995:
4993:
4990:
4988:
4985:
4983:
4980:
4978:
4975:
4973:
4970:
4968:
4965:
4963:
4960:
4958:
4955:
4953:
4950:
4948:
4945:
4943:
4940:
4938:
4935:
4933:
4930:
4928:
4925:
4924:
4922:
4918:
4915:
4909:
4903:
4900:
4898:
4895:
4893:
4890:
4888:
4885:
4883:
4880:
4878:
4875:
4873:
4870:
4868:
4865:
4863:
4860:
4858:
4855:
4853:
4850:
4848:
4845:
4843:
4840:
4838:
4835:
4833:
4830:
4829:
4827:
4825:
4819:
4813:
4810:
4808:
4805:
4803:
4800:
4798:
4795:
4793:
4790:
4788:
4785:
4783:
4780:
4778:
4777:Extremophiles
4775:
4773:
4770:
4768:
4765:
4763:
4760:
4758:
4755:
4753:
4750:
4748:
4745:
4743:
4740:
4738:
4735:
4733:
4730:
4729:
4727:
4723:
4717:
4714:
4712:
4709:
4707:
4704:
4702:
4699:
4697:
4694:
4692:
4689:
4687:
4684:
4682:
4679:
4677:
4674:
4672:
4669:
4667:
4664:
4663:
4661:
4657:
4653:
4646:
4641:
4639:
4634:
4632:
4627:
4626:
4623:
4611:
4608:
4606:
4603:
4601:
4598:
4596:
4593:
4591:
4588:
4586:
4583:
4581:
4578:
4576:
4573:
4571:
4568:
4566:
4563:
4561:
4558:
4556:
4553:
4551:
4548:
4546:
4543:
4541:
4538:
4536:
4533:
4531:
4528:
4526:
4523:
4521:
4518:
4516:
4513:
4512:
4510:
4508:
4504:
4498:
4495:
4493:
4490:
4488:
4485:
4483:
4480:
4478:
4475:
4473:
4470:
4468:
4465:
4463:
4460:
4458:
4455:
4453:
4450:
4449:
4447:
4444:
4443:Fermi paradox
4440:
4434:
4431:
4429:
4426:
4424:
4421:
4419:
4416:
4414:
4411:
4409:
4408:Fermi paradox
4406:
4404:
4401:
4399:
4396:
4394:
4391:
4389:
4386:
4385:
4383:
4379:
4373:
4370:
4368:
4367:Nordic aliens
4365:
4363:
4360:
4358:
4355:
4353:
4350:
4348:
4347:Energy beings
4345:
4344:
4342:
4340:
4334:
4328:
4325:
4323:
4320:
4318:
4315:
4313:
4310:
4308:
4305:
4303:
4300:
4298:
4295:
4293:
4290:
4288:
4285:
4283:
4280:
4278:
4275:
4273:
4270:
4268:
4265:
4263:
4260:
4258:
4255:
4253:
4250:
4246:
4243:
4241:
4238:
4237:
4236:
4233:
4231:
4228:
4226:
4223:
4221:
4218:
4216:
4213:
4211:
4208:
4206:
4203:
4202:
4200:
4198:
4197:communication
4192:
4186:
4185:
4181:
4179:
4178:
4174:
4172:
4169:
4167:
4164:
4162:
4159:
4157:
4155:
4151:
4149:
4146:
4144:
4142:
4138:
4136:
4134:
4130:
4128:
4125:
4123:
4120:
4118:
4115:
4113:
4110:
4108:
4105:
4103:
4100:
4098:
4095:
4093:
4090:
4088:
4085:
4083:
4080:
4078:
4075:
4073:
4070:
4066:
4064:
4060:
4059:
4058:
4055:
4053:
4052:
4048:
4046:
4043:
4041:
4038:
4036:
4035:
4031:
4029:
4028:
4024:
4022:
4020:
4016:
4014:
4011:
4009:
4006:
4004:
4001:
4000:
3998:
3996:
3992:
3986:
3983:
3981:
3978:
3976:
3973:
3971:
3968:
3966:
3963:
3961:
3958:
3956:
3953:
3951:
3948:
3946:
3943:
3941:
3938:
3936:
3933:
3931:
3928:
3926:
3923:
3921:
3918:
3916:
3913:
3911:
3908:
3907:
3905:
3903:
3897:
3891:
3890:Life on Titan
3888:
3886:
3883:
3881:
3880:Life on Venus
3878:
3876:
3873:
3871:
3868:
3867:
3865:
3861:
3848:
3845:
3840:
3837:
3832:
3829:
3824:
3821:
3820:
3818:
3814:
3805:
3802:
3797:
3794:
3789:
3786:
3781:
3778:
3777:
3775:
3771:
3762:
3759:
3754:
3751:
3750:
3748:
3746:Misidentified
3744:
3741:
3737:
3730:
3727:
3724:
3723:Yamato 000593
3721:
3718:
3715:
3712:
3709:
3706:
3703:
3700:
3697:
3694:
3691:
3688:
3685:
3684:
3682:
3678:
3674:
3667:
3662:
3660:
3655:
3653:
3648:
3647:
3644:
3632:
3629:
3627:
3624:
3623:
3621:
3617:
3611:
3608:
3606:
3605:
3601:
3599:
3598:
3594:
3593:
3591:
3589:
3585:
3581:
3574:
3569:
3567:
3562:
3560:
3555:
3554:
3551:
3544:
3541:
3533:
3526:
3523:
3513:
3506:
3503:
3495:
3488:
3485:
3475:
3468:
3465:
3457:
3450:
3446:
3436:
3429:
3426:
3418:
3411:
3408:
3400:
3393:
3390:
3380:
3373:
3370:
3362:
3355:
3344:
3337:
3328:
3321:
3312:
3305:
3296:
3289:
3286:
3278:
3271:
3260:
3253:
3250:
3240:
3233:
3230:
3222:
3212:
3208:
3175:
3171:
3164:
3160:
3156:
3152:
3147:
3143:
3124:
3120:
3113:
3108:
3104:
3100:
3096:
3091:
3087:
3083:
3080:Williams DR.
3078:
3074:
3070:
3069:
3064:
3057:
3053:
3048:
3044:
3040:
3036:
3032:
3028:
3024:
3019:
3015:
3011:
3006:
3002:
2996:
2992:
2991:
2985:
2981:
2977:
2972:
2967:
2962:
2957:
2953:
2949:
2945:
2941:
2937:
2932:
2928:
2924:
2920:
2916:
2912:
2908:
2904:
2900:
2896:
2892:
2886:
2882:
2878:
2874:
2870:
2866:
2862:
2858:
2854:
2850:
2846:
2841:
2837:
2833:
2829:
2825:
2821:
2817:
2813:
2809:
2805:
2801:
2796:
2792:
2788:
2784:
2780:
2776:
2772:
2768:
2764:
2759:
2755:
2751:
2747:
2743:
2739:
2735:
2732:(2): 139–82.
2731:
2727:
2722:
2721:
2716:
2700:
2696:
2689:
2686:
2675:on 2018-10-05
2674:
2670:
2666:
2660:
2657:
2645:
2641:
2634:
2631:
2627:
2621:
2618:
2613:
2609:
2605:
2601:
2597:
2593:
2589:
2585:
2581:
2577:
2570:
2563:
2560:
2549:on 2009-04-08
2548:
2544:
2540:
2533:
2530:
2525:
2521:
2515:
2512:
2507:
2503:
2498:
2493:
2489:
2485:
2481:
2477:
2473:
2469:
2465:
2458:
2455:
2444:on 2016-03-04
2443:
2439:
2433:
2430:
2419:on 2011-01-09
2418:
2414:
2410:
2403:
2401:
2397:
2385:
2381:
2374:
2367:
2364:
2359:
2355:
2350:
2345:
2340:
2335:
2331:
2327:
2323:
2319:
2315:
2308:
2306:
2302:
2297:
2293:
2289:
2285:
2280:
2275:
2271:
2267:
2260:
2257:
2252:
2248:
2244:
2240:
2236:
2232:
2228:
2224:
2220:
2216:
2209:
2206:
2195:
2191:
2184:
2181:
2176:
2172:
2168:
2167:SPIE Newsroom
2161:
2158:
2153:
2149:
2145:
2141:
2137:
2133:
2128:
2123:
2119:
2115:
2108:
2105:
2093:
2089:
2085:
2081:
2077:
2073:
2069:
2065:
2061:
2054:
2051:
2046:
2042:
2037:
2032:
2028:
2024:
2020:
2016:
2013:(6): 515–20.
2012:
2008:
2004:
1997:
1995:
1991:
1986:
1982:
1975:
1972:
1960:
1956:
1950:
1947:
1942:
1938:
1934:
1930:
1926:
1919:
1916:
1910:
1905:
1901:
1897:
1893:
1889:
1885:
1878:
1876:
1872:
1867:
1865:
1857:
1854:
1849:
1845:
1838:
1835:
1832:
1831:0-7167-1766-2
1828:
1824:
1818:
1815:
1803:
1797:
1794:
1789:
1785:
1781:
1777:
1773:
1769:
1766:(4): 545–77.
1765:
1761:
1754:
1751:
1739:
1735:
1731:
1727:
1723:
1719:
1715:
1711:
1707:
1703:
1699:
1692:
1689:
1678:on 2008-05-27
1677:
1673:
1666:
1663:
1658:
1654:
1650:
1646:
1642:
1638:
1631:
1628:
1623:
1619:
1615:
1611:
1607:
1603:
1599:
1595:
1588:
1585:
1580:
1576:
1572:
1568:
1564:
1560:
1556:
1552:
1548:
1544:
1537:
1535:
1533:
1529:
1524:
1520:
1516:
1512:
1508:
1504:
1500:
1496:
1492:
1488:
1481:
1479:
1475:
1463:
1459:
1458:
1453:
1446:
1443:
1437:
1432:
1428:
1424:
1420:
1416:
1412:
1405:
1402:
1398:
1387:on 2020-11-09
1386:
1382:
1378:
1374:
1370:
1366:
1362:
1358:
1354:
1350:
1343:
1340:
1335:
1329:
1325:
1320:
1319:
1310:
1307:
1302:
1298:
1291:
1288:
1276:
1272:
1268:
1264:
1260:
1256:
1252:
1248:
1244:
1240:
1236:
1229:
1226:
1214:
1210:
1206:
1202:
1198:
1194:
1190:
1186:
1182:
1178:
1174:
1167:
1164:
1159:
1155:
1150:
1145:
1141:
1137:
1133:
1129:
1125:
1121:
1117:
1113:
1109:
1102:
1099:
1094:
1087:
1084:
1079:
1075:
1070:
1065:
1061:
1057:
1053:
1049:
1045:
1038:
1035:
1030:
1026:
1022:
1018:
1014:
1010:
1003:
1000:
994:
989:
985:
981:
977:
973:
969:
962:
960:
956:
945:on 2010-11-03
944:
940:
933:
931:
927:
916:
910:
906:
905:
897:
895:
891:
886:
880:
876:
875:
867:
864:
859:
847:
839:
833:
828:
827:
818:
815:
807:
801:
798:
793:
789:
785:
781:
777:
773:
769:
765:
758:
755:
743:
737:
734:
729:
723:
719:
718:
710:
708:
706:
704:
702:
698:
691:
685:
682:
680:
679:
675:
673:
672:
668:
666:
663:
661:
658:
656:
653:
651:
648:
646:
643:
640:
637:
635:
632:
631:
626:
624:
622:
618:
617:Phoenix Scout
614:
610:
606:
602:
597:
593:
589:
585:
580:
573:
571:
567:
565:
561:
557:
552:
550:
546:
542:
541:biosignatures
536:
534:
530:
524:
509:
501:
499:
495:
492:
488:
487:chloromethane
484:
480:
476:
472:
470:
464:
461:
457:
453:
449:
445:
439:
435:
431:
427:
421:
418:
414:
405:
403:
400:
399:cyanobacteria
396:
392:
388:
384:
381:
377:
369:
365:
361:
357:
353:
345:
343:
341:
337:
333:
332:peer reviewed
329:
324:
322:
321:cyanobacteria
318:
313:
307:
302:
297:
292:
289:
281:
277:
276:exobiologists
273:
272:Gilbert Levin
269:
261:
259:
255:
253:
249:
245:
237:
233:
229:
225:
221:
213:
211:
209:
204:
200:
196:
192:
188:
187:chloromethane
183:
181:
177:
172:
168:
164:
162:
156:
154:
150:
146:
142:
137:
135:
134:Klaus Biemann
131:
127:
123:
119:
115:
107:
105:
104:(NASA Ames).
103:
96:Viking lander
94:
87:
85:
83:
79:
74:
72:
69:of microbial
68:
67:biosignatures
64:
63:
58:
57:
52:
48:
45:
41:
32:
19:
5453:
5441:
5350:and programs
5348:Institutions
5166:
5148:
5126:Heliocentric
5114:
5102:
5084:
5070:
5057:
5049:Perseverance
5048:
5033:
4837:Earth analog
4824:habitability
4792:Ocean planet
4762:Earth analog
4747:Biosignature
4706:Paleontology
4701:Microbiology
4681:Biochemistry
4671:Astrophysics
4652:Astrobiology
4605:UFO religion
4550:Extremophile
4530:Biosignature
4525:Astroecology
4520:Astrobiology
4472:Great Filter
4287:Project Ozma
4195:Interstellar
4182:
4175:
4153:
4141:Perseverance
4140:
4132:
4062:
4049:
4032:
4025:
4018:
3920:Earth analog
3902:habitability
3885:Life on Mars
3704:
3609:
3602:
3595:
3539:
3521:
3501:
3483:
3463:
3445:Schiaparelli
3444:
3424:
3406:
3389:Perseverance
3388:
3368:
3284:
3268:Deep Space 2
3248:
3228:
3185: Active
3173:
3123:the original
3118:
3103:the original
3098:
3085:
3055:
3026:
3022:
3013:
2989:
2943:
2939:
2894:
2890:
2848:
2844:
2803:
2799:
2766:
2762:
2729:
2725:
2703:. Retrieved
2699:the original
2688:
2677:. Retrieved
2673:the original
2668:
2659:
2648:. Retrieved
2643:
2633:
2620:
2579:
2575:
2562:
2551:. Retrieved
2547:the original
2542:
2532:
2523:
2514:
2471:
2468:Astrobiology
2467:
2457:
2446:. Retrieved
2442:the original
2432:
2421:. Retrieved
2417:the original
2412:
2388:. Retrieved
2383:
2379:
2366:
2321:
2317:
2272:(2): 39–47.
2269:
2265:
2259:
2221:(1): 59–72.
2218:
2214:
2208:
2197:. Retrieved
2193:
2183:
2166:
2160:
2117:
2113:
2107:
2097:27 September
2095:. Retrieved
2067:
2064:Astrobiology
2063:
2053:
2010:
2007:Astrobiology
2006:
1984:
1974:
1963:. Retrieved
1961:. 2010-09-05
1959:ScienceDaily
1958:
1949:
1924:
1918:
1891:
1887:
1863:
1856:
1847:
1837:
1822:
1817:
1806:. Retrieved
1796:
1763:
1760:Astrobiology
1759:
1753:
1743:27 September
1741:. Retrieved
1705:
1701:
1691:
1680:. Retrieved
1676:the original
1665:
1640:
1636:
1630:
1597:
1593:
1587:
1546:
1542:
1490:
1486:
1466:. Retrieved
1462:the original
1455:
1445:
1421:(1): 14–26.
1418:
1414:
1404:
1395:
1389:. Retrieved
1385:the original
1356:
1352:
1342:
1317:
1309:
1300:
1290:
1280:27 September
1278:. Retrieved
1242:
1238:
1228:
1218:27 September
1216:. Retrieved
1180:
1176:
1166:
1115:
1112:Astrobiology
1111:
1101:
1086:
1054:(A32): A32.
1051:
1047:
1037:
1012:
1008:
1002:
975:
971:
947:. Retrieved
943:the original
918:. Retrieved
903:
873:
866:
825:
817:
800:
767:
763:
757:
746:. Retrieved
736:
716:
676:
669:
660:Life on Mars
645:Biosignature
634:Astrobiology
608:
577:
568:
556:Mario Crocco
553:
537:
525:
505:
496:
482:
478:
468:
465:
446:
422:
412:
409:
351:
349:
330:published a
325:
314:
301:astrobiology
293:
267:
265:
256:
219:
217:
214:Gas exchange
184:
179:
175:
170:
160:
157:
152:
149:astrobiology
138:
117:
111:
99:
81:
77:
75:
71:life on Mars
60:
54:
37:
5283:undeveloped
5133:BioSentinel
5023:Fobos-Grunt
4920:Earth orbit
4742:Biomolecule
4732:Abiogenesis
4725:Main topics
4659:Disciplines
4540:Exotheology
4352:Grey aliens
4205:Active SETI
4133:Opportunity
4013:BioSentinel
3831:Wow! signal
3780:KIC 8462852
3729:CI1 fossils
3369:Opportunity
3205:(See also:
854:|work=
531:-saturated
508:perchlorate
502:Controversy
475:perchlorate
430:ozone layer
380:radioactive
306:superoxides
288:metabolized
280:Miller-Urey
224:Vance Oyama
167:perchlorate
47:experiments
5471:Categories
5330:Red Dragon
5110:OSIRIS-REx
5094:Comets and
4797:Panspermia
4575:Noogenesis
4555:Hemolithin
4433:Panspermia
4381:Hypotheses
4357:Insectoids
4322:Water hole
3823:SHGb02+14a
3796:VVV-WIT-07
2705:2007-05-31
2679:2009-07-26
2650:2009-07-26
2553:2009-02-10
2448:2014-04-14
2423:2011-01-07
2390:2008-08-14
2199:2020-01-13
2120:(2): 147.
1965:2010-09-23
1808:2014-04-14
1682:2008-10-13
1643:(3): 666.
1468:2013-07-16
1391:2015-03-22
1359:: 96–108.
949:2010-10-24
920:2013-07-16
748:2014-04-14
692:References
417:metabolism
360:atmosphere
44:biological
5247:Laplace-P
5150:Dragonfly
5104:Hayabusa2
5096:asteroids
5065:Tianwen-1
5043:Mars 2020
5034:Curiosity
4967:Eu:CROPIS
4822:Planetary
4445:solutions
4312:setiQuest
4307:SETI@home
4122:Mars 2020
4097:Laplace-P
4034:Dragonfly
4019:Curiosity
3900:Planetary
3464:Sojourner
3249:Curiosity
3056:Space.com
2524:wustl.edu
2413:Space.com
2296:1850-1826
2279:0705.3176
1738:133854625
1730:2169-9100
1622:189797714
1523:206569558
1140:1557-8070
1078:236336984
856:ignored (
846:cite book
621:hydrazine
609:Sojourner
574:Critiques
564:metabolic
554:In 2006,
473:detected
413:Curiosity
376:carbon-14
366:(CO) and
5443:Category
5305:Kazachok
5295:Beagle 3
5227:ExoLance
5180:Proposed
5018:Beagle 2
4992:OREOcube
4972:EXOSTACK
4913:missions
4297:SERENDIP
4272:NIROSETI
4184:Viking 2
4177:Viking 1
4082:Foton-M3
4072:ExoLance
4003:Beagle 2
3604:Viking 2
3597:Viking 1
3540:Viking 2
3522:Viking 1
3229:Beagle 2
3207:Mars map
3043:17972399
2980:17548829
2927:22532319
2919:17793082
2881:22910940
2873:11537541
2828:10666745
2644:BBC News
2612:43194305
2604:24051245
2506:27626510
2358:17060639
2243:10077869
2092:28418706
2045:23746165
1788:17723090
1579:24957458
1571:17793090
1515:17797093
1381:96639386
1275:20915236
1213:24206165
1205:17797094
1158:27626510
792:39294965
742:"ch11-5"
678:Viking 2
671:Viking 1
627:See also
479:Viking 1
426:UV light
248:hydrogen
244:nitrogen
82:Viking 2
78:Viking 1
62:Viking 2
56:Viking 1
5455:Commons
5272:Trident
5262:Oceanus
5161:ExoMars
5142:Planned
5116:Rosetta
5071:Zhurong
5059:Phoenix
4997:Tanpopo
4987:O/OREOS
4932:BIOCORE
4161:Tanpopo
4057:ExoMars
3761:CTA-102
3753:CP 1919
3619:Related
3502:Zhurong
3407:Phoenix
3285:InSight
3163:landers
3153:of the
3146:discuss
2971:1965509
2948:Bibcode
2899:Bibcode
2891:Science
2853:Bibcode
2808:Bibcode
2791:4206764
2771:Bibcode
2734:Bibcode
2584:Bibcode
2576:Science
2497:6445182
2476:Bibcode
2349:1621051
2326:Bibcode
2284:Bibcode
2223:Bibcode
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