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Panspermia proposes that organisms such as bacteria, complete with their DNA, could be transported by means such as comets through space to planets including Earth.

Panspermia (from Ancient Greek πᾶν (pan)  'all ', and σπέρμα (sperma)  'seed') is the hypothesis that life exists throughout the Universe, distributed by space dust,[1] meteoroids,[2] asteroids, comets,[3] and planetoids,[4] as well as by spacecraft carrying unintended contamination by microorganisms.[5][6][7] Panspermia is a fringe theory with little support amongst mainstream scientists.[8] Critics argue that it does not answer the question of the origin of life but merely places it on another celestial body. It is also criticized because it cannot be tested experimentally.[9]

Panspermia proposes that microscopic lifeforms which can survive the effects of space (such as extremophiles) can become trapped in debris ejected into space after collisions between planets and small Solar System bodies that harbor life.[10] Panspermia studies concentrate not on how life began but on methods that may distribute it in the Universe.[11][12][13]

Pseudo-panspermia (sometimes called soft panspermia or molecular panspermia) is the well-attested hypothesis that many of the pre-biotic organic building-blocks of life originated in space, became incorporated in the solar nebula from which planets condensed, and were further—and continuously—distributed to planetary surfaces where life then emerged.[14][15]


The first mention of panspermia was in the writings of the fifth-century BC Greek philosopher Anaxagoras.[16][17] Panspermia began to assume a more scientific form through the proposals of Jöns Jacob Berzelius (1834),[18] Hermann E. Richter (1865),[19] Kelvin (1871),[20] Hermann von Helmholtz (1879)[21][22] and finally reaching the level of a detailed scientific hypothesis through the efforts of the Swedish chemist Svante Arrhenius (1903).[23]

Fred Hoyle (1915–2001) and Chandra Wickramasinghe (born 1939) were influential proponents of panspermia.[24][25] In 1974 they proposed the hypothesis that some dust in interstellar space was largely organic (containing carbon), which Wickramasinghe later proved to be correct.[26][27][28] Hoyle and Wickramasinghe further contended that life forms continue to enter the Earth's atmosphere, and may be responsible for epidemic outbreaks, new diseases, and the genetic novelty necessary for macroevolution.[29]


Core requirements[edit]

Panspermia requires:

  1. that organic molecules originated in space (perhaps to be distributed to Earth)
  2. that life originated from these molecules, extraterrestrially
  3. that this extraterrestrial life was transported to Earth.

The creation and distribution of organic molecules from space is now uncontroversial; it is known as pseudo-panspermia.[14] The existence of extraterrestrial life is unconfirmed but scientifically possible.[30]

Interstellar or interplanetary[edit]

Some microbes appear able to survive the planetary protection procedures applied to spacecraft in cleanrooms, intended to prevent accidental planetary contamination.[5][6]

Panspermia can be said to be either interstellar (between star systems) or interplanetary (between planets in the same star system).[31][32]

The major proposed mechanisms for panspermia are radiopanspermia, the propulsion of microbes through space by radiation pressure;[33] lithopanspermia, the transfer of organisms inside rocks, shielded from the space environment;[34] and directed panspermia, managed deliberately to seed planetary systems with life.[35]

Space probes may be a viable transport mechanism for interplanetary cross-pollination within the Solar System. Space agencies have implemented planetary protection procedures to reduce the risk of planetary contamination,[36][37] but microorganisms such as Tersicoccus phoenicis may be resistant to spacecraft assembly cleaning.[5][6]

Origination and distribution of organic molecules: Pseudo-panspermia[edit]

Pseudo-panspermia is the well-supported hypothesis that many of the small organic molecules used for life originated in space, and were distributed to planetary surfaces. Life then emerged on Earth, and perhaps on other planets, by the processes of abiogenesis.[14][15] Evidence for pseudo-panspermia includes the discovery of organic compounds such as sugars, amino acids, and nucleobases in meteorites and other extraterrestrial bodies,[38][39][40][41][42] and the formation of similar compounds in the laboratory under outer space conditions.[43][44][45][46] A prebiotic polyester system has been explored as an example.[47][48]



In 1903, Svante Arrhenius proposed radiopanspermia, that microscopic forms of life can be propagated in space, driven by the radiation pressure from stars.[33][49] Arrhenius argued that particles at a critical size below 1.5 μm would be propelled at high speed by radiation pressure of the Sun. However, because its effectiveness decreases with increasing size of the particle, this mechanism holds for very tiny particles only, such as single bacterial spores.[50]


The main criticism of radiopanspermia came from Iosif Shklovsky and Carl Sagan, who pointed out the evidence for the lethal action of space radiation (UV and X-rays) in the cosmos.[51] Regardless of the evidence, Wallis and Wickramasinghe argued in 2004 that the transport of individual bacteria or clumps of bacteria, is overwhelmingly more important than lithopanspermia in terms of numbers of microbes transferred, even accounting for the death rate of unprotected bacteria in transit.[52]

Data gathered by the orbital experiments ERA, BIOPAN, EXOSTACK and EXPOSE showed that isolated spores, including those of B. subtilis, were rapidly killed if exposed to the full space environment for merely a few seconds, but if shielded against solar UV, the spores were capable of surviving in space for up to six years while embedded in clay or meteorite powder (artificial meteorites).[50][53] Spores would therefore need to be heavily protected against UV radiation: exposure of unprotected DNA to solar UV and cosmic ionizing radiation would break it up into its constituent bases.[54][55][56] Also, exposing DNA to the ultrahigh vacuum of space alone is sufficient to cause DNA damage, so the transport of unprotected DNA or RNA during interplanetary flights powered solely by light pressure is extremely unlikely.[56]

The feasibility of other means of transport for the more massive shielded spores into the outer Solar System—for example, through gravitational capture by comets—is unknown. Rocks at least 1 meter in diameter are required to effectively shield resistant microorganisms, such as bacterial spores against galactic cosmic radiation.[57][58] These results clearly negate the radiopanspermia hypothesis.[50][53]



Lithopanspermia, the transfer of organisms in rocks from one planet to another either through interplanetary or interstellar space, such as in comets or asteroids,[59][60][61][34] remains speculative.[62][63]

A variant would be for organisms to travel between star systems on nomadic exoplanets or exomoons.[64]

The travel of rocks between stars in our galaxy is estimated to take millions of years, which is less than the billions of years that life on Earth has evolved.[65]

Although there is no evidence that lithopanspermia has occurred in the Solar System, the various stages have become amenable to experimental testing.[9]

  • Planetary ejection – For lithopanspermia to occur, microorganisms must survive ejection from a planetary surface, which involves extreme forces of acceleration and shock with associated temperature excursions. Hypothetical values of shock pressures experienced by ejected rocks are obtained with Martian meteorites, which suggest the shock pressures of approximately 5 to 55 GPa, acceleration of 3 Mm/s2 and jerk of 6 Gm/s3 and post-shock temperature increases of about 1 K to 1000 K. Some organisms appear able to survive these conditions.[66][67]
  • Survival in transit – The survival of microorganisms has been studied extensively using both simulated facilities and in low Earth orbit. A large number of microorganisms have been selected for exposure experiments, both human-borne microbes (significant for future crewed missions) and extremophiles (significant for determining the physiological requirements of survival in space).[9]
  • Atmospheric entry – to test whether microbes on or within rocks could survive hypervelocity entry through Earth's atmosphere.[66] Tests could use sounding rockets and orbital vehicles.[9][66] B. subtilis spores inoculated onto granite domes were twice subjected to hypervelocity atmospheric transit by launch to a ~120 km altitude on an Orion two-stage rocket. The spores survived on the sides of the rock, but not on the forward-facing surface that reached 145 °C.[68] As photosynthetic organisms must be close to the surface of a rock to obtain sufficient light energy, atmospheric transit might act as a filter against them by ablating the surface layers of the rock. Although cyanobacteria can survive the desiccating, freezing conditions of space, the STONE experiment showed that they cannot survive atmospheric entry.[69] Small non-photosynthetic organisms deep within rocks might survive the exit and entry process, including impact survival.[70][71]

Directed panspermia[edit]


Directed panspermia would be the deliberate transport of microorganisms in space, sent to Earth to start life here, or sent from Earth to seed new planetary systems with life by introduced species of microorganisms on lifeless planets.[72][73][74][75] The Nobel prize winner Francis Crick, along with Leslie Orgel proposed that life may have been purposely spread by an advanced extraterrestrial civilization,[35] but considering an early "RNA world" Crick noted later that life may have originated on Earth.[76][57] The astronomer Thomas Gold suggested in 1960 the hypothesis of "Cosmic Garbage", that life on Earth might have originated accidentally from a pile of waste products dumped on Earth long ago by extraterrestrial beings.[77]


Directed panspermia could, in theory, be demonstrated by finding a distinctive 'signature' message had been deliberately implanted into either the genome or the genetic code of the first microorganisms by our hypothetical progenitor, some 4 billion years ago. It has been suggested that the bacteriophage φX174 might represent such a message. However, there is no known mechanism that could prevent mutation and natural selection from removing such a message over long periods of time.[78][79][80][81]


A separate fragment of the Orgueil meteorite (kept in a sealed glass jar since its discovery) was found in 1965 to have a seed capsule embedded in it, while the original glassy layer on the outside remained undisturbed. Despite great initial excitement, the seed was found to be that of a European Juncaceae or rush plant that had been glued into the fragment and camouflaged using coal dust. The outer "fusion layer" was in fact glue. While the perpetrator of this hoax is unknown, it is thought that they sought to influence the 19th-century debate on spontaneous generation—rather than panspermia—by demonstrating the transformation of inorganic to biological matter.[82]

See also[edit]


  1. ^ Berera, Arjun (6 November 2017). "Space dust collisions as a planetary escape mechanism". Astrobiology. 17 (12): 1274–1282. arXiv:1711.01895. Bibcode:2017AsBio..17.1274B. doi:10.1089/ast.2017.1662. PMID 29148823. S2CID 126012488.
  2. ^ Chan, Queenie H. S.; et al. (10 January 2018). "Organic matter in extraterrestrial water-bearing salt crystals". Science Advances. 4 (1): eaao3521. Bibcode:2018SciA....4.3521C. doi:10.1126/sciadv.aao3521. PMC 5770164. PMID 29349297.
  3. ^ Wickramasinghe, Chandra (2011). "Bacterial morphologies supporting cometary panspermia: a reappraisal". International Journal of Astrobiology. 10 (1): 25–30. Bibcode:2011IJAsB..10...25W. CiteSeerX doi:10.1017/S1473550410000157. S2CID 7262449.
  4. ^ Rampelotto, P. H. (2010). "Panspermia: A promising field of research" (PDF). Astrobiology Science Conference. 1538: 5224. Bibcode:2010LPICo1538.5224R.
  5. ^ a b c Forward planetary contamination like Tersicoccus phoenicis, that has shown resistance to methods usually used in spacecraft assembly clean rooms: Madhusoodanan, Jyoti (May 19, 2014). "Microbial stowaways to Mars identified". Nature. doi:10.1038/nature.2014.15249. S2CID 87409424.
  6. ^ a b c Webster, Guy (November 6, 2013). "Rare New Microbe Found in Two Distant Clean Rooms". Retrieved November 6, 2013.
  7. ^ Staff – Purdue University (27 February 2018). "Tesla in space could carry bacteria from Earth". Retrieved 28 February 2018.
  8. ^ May, Andrew (2019). Astrobiology: The Search for Life Elsewhere in the Universe. London. ISBN 978-1785783425. OCLC 999440041. Although they were part of the scientific establishment—Hoyle at Cambridge and Wickramasinghe at the University of Wales—their views on the topic were far from mainstream, and panspermia remains a fringe theory{{cite book}}: CS1 maint: location missing publisher (link)
  9. ^ a b c d Olsson-Francis, Karen; Cockell, Charles S. (2010). "Experimental methods for studying microbial survival in extraterrestrial environments". Journal of Microbiological Methods. 80 (1): 1–13. doi:10.1016/j.mimet.2009.10.004. PMID 19854226.
  10. ^ Chotiner, Isaac (8 July 2019). "What If Life Did Not Originate on Earth?". The New Yorker. Retrieved 10 July 2019.
  11. ^ A variation of the panspermia hypothesis is necropanspermia which astronomer Paul Wesson describes as follows: "The vast majority of organisms reach a new home in the Milky Way in a technically dead state … Resurrection may, however, be possible." Grossman, Lisa (2010-11-10). "All Life on Earth Could Have Come From Alien Zombies". Wired. Retrieved 10 November 2010.
  12. ^ Hoyle, F. and Wickramasinghe, N.C. (1981). Evolution from Space. Simon & Schuster, New York, and J.M. Dent and Son, London (1981), ch. 3 pp. 35–49.
  13. ^ Wickramasinghe, J., Wickramasinghe, C. and Napier, W. (2010). Comets and the Origin of Life. World Scientific, Singapore. ch. 6 pp. 137–154. ISBN 978-9812566355
  14. ^ a b c Klyce, Brig (2001). "Panspermia Asks New Questions". Retrieved 25 July 2013.
  15. ^ a b Klyce, Brig (2001). "Panspermia asks new questions". In Kingsley, Stuart A; Bhathal, Ragbir (eds.). The Search for Extraterrestrial Intelligence (SETI) in the Optical Spectrum III. Vol. 4273. pp. 11–14. Bibcode:2001SPIE.4273...11K. doi:10.1117/12.435366. S2CID 122849901. {{cite book}}: |journal= ignored (help)
  16. ^ Hollinger, Maik (2016). "Life from Elsewhere – Early History of the Maverick Theory of Panspermia". Sudhoffs Archiv. 100 (2): 188–205. doi:10.25162/sudhoff-2016-0009. JSTOR 24913787. PMID 29668166. S2CID 4942706.
  17. ^ Kolb, Vera M.; Clark III, Benton C. (2020). "10". Astrobiology for a General Reader: A Question and Answers – Panspermia hypothesis. Cambridge Scholars Publishing. p. 47. ISBN 978-1527555020. Retrieved 3 May 2022. The Panspermia hypothesis states that life exists elsewhere in the universe, and could be distributed far and wide. This idea was first introduced by the ancient Greek philosopher Anaxagoras (5th Century BCE), who believed that the universe is made of an infinite number of seeds ("spermata" in Greek). Upon reaching the Earth, these seeds gave rise to life. Anaxagorus introduced the term "Panspermia", which in Greek means literally "seeds everywhere".
  18. ^ Berzelius, J. J. (1834). "Analysis of the Alais meteorite and implications about life in other worlds". Liebigs Annalen der Chemie und Pharmacie. 10: 134–135.
  19. ^ Rothschild, Lynn J.; Lister, Adrian M. (June 2003). Evolution on Planet Earth – The Impact of the Physical Environment. Academic Press. pp. 109–127. ISBN 978-0125986557.
  20. ^ Thomson (Lord Kelvin), W. (1871). "Inaugural Address to the British Association Edinburgh. 'We must regard it as probably to the highest degree that there are countless seed-bearing meteoritic stones moving through space.'". Nature. 4 (92): 261–278 [262]. Bibcode:1871Natur...4..261.. doi:10.1038/004261a0. PMC 2070380.
  21. ^ "The word: Panspermia". New Scientist. No. 2541. 7 March 2006. Retrieved 25 July 2013.
  22. ^ "History of Panspermia". Archived from the original on 13 October 2014. Retrieved 25 July 2013.
  23. ^ Arrhenius, S. (1908). Worlds in the Making: The Evolution of the Universe. New York: Harper & Row.
  24. ^ Napier, W.M. (2007). "Pollination of exoplanets by nebulae". International Journal of Astrobiology. 6 (3): 223–228. Bibcode:2007IJAsB...6..223N. doi:10.1017/S1473550407003710. S2CID 122742509.
  25. ^ Line, M.A. (2007). "Panspermia in the context of the timing of the origin of life and microbial phylogeny". Int. J. Astrobiol. 3. 6 (3): 249–254. Bibcode:2007IJAsB...6..249L. doi:10.1017/S1473550407003813. S2CID 86569201.
  26. ^ Wickramasinghe, D. T.; Allen, D. A. (1980). "The 3.4-µm interstellar absorption feature". Nature. 287 (5782): 518–519. Bibcode:1980Natur.287..518W. doi:10.1038/287518a0. S2CID 4352356.
  27. ^ Allen, D. A.; Wickramasinghe, D. T. (1981). "Diffuse interstellar absorption bands between 2.9 and 4.0 µm". Nature. 294 (5838): 239–240. Bibcode:1981Natur.294..239A. doi:10.1038/294239a0. S2CID 4335356.
  28. ^ Wickramasinghe, D. T.; Allen, D. A. (1983). "Three components of 3–4 μm absorption bands". Astrophysics and Space Science. 97 (2): 369–378. Bibcode:1983Ap&SS..97..369W. doi:10.1007/BF00653492. S2CID 121109158.
  29. ^ Hoyle, Fred; Wickramasinghe, Chandra; Watson, John (1986). Viruses from Space and Related Matters. University College Cardiff Press.
  30. ^ Pickrell, John (4 September 2006). "Top 10: Controversial pieces of evidence for extraterrestrial life". New Scientist. Retrieved 18 February 2011.
  31. ^ Khan, Amina (7 March 2014). "Did two planets around nearby star collide? Toxic gas holds hints". LA Times. Retrieved 9 March 2014.
  32. ^ Dent, W. R. F.; Wyatt, M. C.; Roberge, A.; et al. (6 March 2014). "Molecular Gas Clumps from the Destruction of Icy Bodies in the β Pictoris Debris Disk". Science. 343 (6178): 1490–1492. arXiv:1404.1380. Bibcode:2014Sci...343.1490D. doi:10.1126/science.1248726. PMID 24603151. S2CID 206553853.
  33. ^ a b Arrhenius, Svante (1903). "Die Verbreitung des Lebens im Weltenraum" [The Distribution of Life in Space]. Die Umschau (in German).
  34. ^ a b Mileikowsky, C.; Cucinotta, F. A.; Wilson, J. W. Wilson; et al. (2000). "Risks threatening viable transfer of microbes between bodies in our solar system". Planetary and Space Science. 48 (11): 1107–1115. Bibcode:2000P&SS...48.1107M. doi:10.1016/S0032-0633(00)00085-4.
  35. ^ a b Crick, F. H.; Orgel, L. E. (1973). "Directed Panspermia". Icarus. 19 (3): 341–348. Bibcode:1973Icar...19..341C. CiteSeerX doi:10.1016/0019-1035(73)90110-3.
  36. ^ "Studies Focus On Spacecraft Sterilization". The Aerospace Corporation. July 30, 2000. Archived from the original on 2006-05-02.
  37. ^ "Dry heat sterilisation process to high temperatures". European Space Agency. 22 May 2006. Archived from the original on 2012-02-01.
  38. ^ Steigerwald, Bill; Jones, Nancy; Furukawa, Yoshihiro (18 November 2019). "First Detection of Sugars in Meteorites Gives Clues to Origin of Life". NASA. Retrieved 18 November 2019.
  39. ^ Furukawa, Yoshihiro; et al. (18 November 2019). "Extraterrestrial ribose and other sugars in primitive meteorites". Proceedings of the National Academy of Sciences of the United States of America. 116 (49): 24440–24445. Bibcode:2019PNAS..11624440F. doi:10.1073/pnas.1907169116. PMC 6900709. PMID 31740594.
  40. ^ Furukawa, Yoshihiro; Chikaraishi, Yoshito; Ohkouchi, Naohiko; et al. (13 November 2019). "Extraterrestrial ribose and other sugars in primitive meteorites". Proceedings of the National Academy of Sciences. 116 (49): 24440–24445. Bibcode:2019PNAS..11624440F. doi:10.1073/pnas.1907169116. PMC 6900709. PMID 31740594.
  41. ^ Martins, Zita; Botta, Oliver; Fogel, Marilyn L.; et al. (2008). "Extraterrestrial nucleobases in the Murchison meteorite". Earth and Planetary Science Letters. 270 (1–2): 130–136. arXiv:0806.2286. Bibcode:2008E&PSL.270..130M. doi:10.1016/j.epsl.2008.03.026. S2CID 14309508.
  42. ^ Rivilla, Víctor M.; Jiménez-Serra, Izaskun; Martín-Pintado, Jesús; Colzi, Laura; Tercero, Belén; de Vicente, Pablo; Zeng, Shaoshan; Martín, Sergio; García de la Concepción, Juan; Bizzocchi, Luca; Melosso, Mattia (2022). "Molecular Precursors of the RNA-World in Space: New Nitriles in the G+0.693−0.027 Molecular Cloud". Frontiers in Astronomy and Space Sciences. 9: 876870. arXiv:2206.01053. Bibcode:2022FrASS...9.6870R. doi:10.3389/fspas.2022.876870. ISSN 2296-987X.
  43. ^ Marlaire, Ruth (3 March 2015). "NASA Ames Reproduces the Building Blocks of Life in Laboratory". NASA. Retrieved 5 March 2015.
  44. ^ Krasnokutski, S.A.; Chuang, K. J.; Jäger, C.; et al. (2022). "A pathway to peptides in space through the condensation of atomic carbon". Nature Astronomy. 6 (3): 381–386. arXiv:2202.12170. Bibcode:2022NatAs...6..381K. doi:10.1038/s41550-021-01577-9. S2CID 246768607.
  45. ^ Sithamparam, Mahendran; Satthiyasilan, Nirmell; Chen, Chen; Jia, Tony Z.; Chandru, Kuhan (2022-02-11). "A material‐based panspermia hypothesis: The potential of polymer gels and membraneless droplets". Biopolymers. 113 (5): e23486. arXiv:2201.06732. doi:10.1002/bip.23486. PMID 35148427. S2CID 246016331.
  46. ^ Comte, Denis; Lavy, Léo; Bertier, Paul; Calvo, Florent; Daniel, Isabelle; Farizon, Bernadette; Farizon, Michel; Märk, Tilmann D. (2023-01-26). "Glycine Peptide Chain Formation in the Gas Phase via Unimolecular Reactions". The Journal of Physical Chemistry A. 127 (3): 775–780. Bibcode:2023JPCA..127..775C. doi:10.1021/acs.jpca.2c08248. ISSN 1089-5639. PMID 36630603. S2CID 255748895.
  47. ^ Chandru; Mamajanov; Cleaves; Jia (2020-01-19). "Polyesters as a Model System for Building Primitive Biologies from Non-Biological Prebiotic Chemistry". Life. 10 (1): 6. Bibcode:2020Life...10....6C. doi:10.3390/life10010006. PMC 7175156. PMID 31963928.
  48. ^ Jia, Tony Z.; Chandru, Kuhan; Hongo, Yayoi; Afrin, Rehana; Usui, Tomohiro; Myojo, Kunihiro; Cleaves, H. James (2019-08-06). "Membraneless polyester microdroplets as primordial compartments at the origins of life". Proceedings of the National Academy of Sciences. 116 (32): 15830–15835. Bibcode:2019PNAS..11615830J. doi:10.1073/pnas.1902336116. PMC 6690027. PMID 31332006.
  49. ^ Nicholson, Wayne L. (2009). "Ancient micronauts: Interplanetary transport of microbes by cosmic impacts". Trends in Microbiology. 17 (6): 243–250. doi:10.1016/j.tim.2009.03.004. PMID 19464895.
  50. ^ a b c Horneck, G.; Klaus, D. M.; Mancinelli, R. L. (2010). "Space Microbiology". Microbiology and Molecular Biology Reviews. 74 (1): 121–156. Bibcode:2010MMBR...74..121H. doi:10.1128/MMBR.00016-09. PMC 2832349. PMID 20197502.
  51. ^ Shklovskii, I. S.; Sagan, Carl (1966). Intelligent Life in the Universe. Emerson-Adams Press. ISBN 978-1892803023.[page needed]
  52. ^ Wickramasinghe, M.K.; Wickramasinghe, C. (2004). "Interstellar transfer of planetary microbiota". Monthly Notices of the Royal Astronomical Society. 348 (1): 52–57. Bibcode:2004MNRAS.348...52W. doi:10.1111/j.1365-2966.2004.07355.x.
  53. ^ a b Horneck, G.; Rettberg, P.; Reitz, G.; et al. (2001). "Protection of bacterial spores in space, a contribution to the discussion on panspermia". Origins of Life and Evolution of the Biosphere. 31 (6): 527–547. Bibcode:2002ESASP.518..105R. doi:10.1023/A:1012746130771. PMID 11770260. S2CID 24304433.
  54. ^ Rahn, R.O.; Hosszu, J.L. (1969). "Influence of relative humidity on the photochemistry of DNA films". Biochim. Biophys. Acta. 190 (1): 126–131. doi:10.1016/0005-2787(69)90161-0. PMID 4898489.
  55. ^ Patrick, M.H.; Gray, D.M. (1976). "Independence of photproduct formation on DNA conformation". Photochem. Photobiol. 24 (6): 507–513. doi:10.1111/j.1751-1097.1976.tb06867.x. PMID 1019243. S2CID 12711656.
  56. ^ a b Nicholson, Wayne L.; Schuerger, Andrew C.; Setlow, Peter (21 January 2005). "The solar UV environment and bacterial spore UV resistance: considerations for Earth-to-Mars transport by natural processes and human spaceflight" (PDF). Mutation Research. 571 (1–2): 249–264. doi:10.1016/j.mrfmmm.2004.10.012. PMID 15748651. Archived from the original (PDF) on 28 December 2013. Retrieved 2 August 2013.
  57. ^ a b Clark, Benton C. (February 2001). "Planetary Interchange of Bioactive Material: Probability Factors and Implications". Origins of Life and Evolution of the Biosphere. 31 (1–2): 185–197. Bibcode:2001OLEB...31..185C. doi:10.1023/A:1006757011007. PMID 11296521. S2CID 12580294.
  58. ^ Mileikowsky, C.; Cucinotta, F.A.; Wilson, J.W.; et al. (2000). "Natural transfer of microbes in space, part I: from Mars to Earth and Earth to Mars". Icarus. 145 (2): 391–427. Bibcode:2000Icar..145..391M. doi:10.1006/icar.1999.6317. PMID 11543506.
  59. ^ Wall, Mike. "Comet Impacts May Have Jump-Started Life on Earth". Retrieved 1 August 2013.
  60. ^ Weber, P; Greenberg, J. M. (1985). "Can spores survive in interstellar space?". Nature. 316 (6027): 403–407. Bibcode:1985Natur.316..403W. doi:10.1038/316403a0. S2CID 4351813.
  61. ^ Melosh, H. J. (1988). "The rocky road to panspermia". Nature. 332 (6166): 687–688. Bibcode:1988Natur.332..687M. doi:10.1038/332687a0. PMID 11536601. S2CID 30762112.
  62. ^ Belbruno, Edward; Moro-Martı´n, Amaya; Malhotra, Renu; et al. (2012). "Chaotic Exchange of Solid Material between Planetary". Astrobiology. 12 (8): 754–774. arXiv:1205.1059. Bibcode:2012AsBio..12..754B. doi:10.1089/ast.2012.0825. PMC 3440031. PMID 22897115.
  63. ^ Kelly, Morgan (September 24, 2012). "Slow-moving rocks better odds that life crashed to Earth from space". Princeton University.
  64. ^ Sadlok, Grzegorz (2020-02-07). "On A Hypothetical Mechanism of Interstellar Life Transfer Trough Nomadic Objects". Origins of Life and Evolution of Biospheres. 50 (1–2): 87–96. Bibcode:2020OLEB...50...87S. doi:10.1007/s11084-020-09591-z. PMID 32034615.
  65. ^ Wallis, Max W.; Wickramasinghe, N.C. (February 2004). "Interstellar transfer of planetary microbiota". Monthly Notices of the Royal Astronomical Society. 348 (1): 52–61. Bibcode:2004MNRAS.348...52W. doi:10.1111/j.1365-2966.2004.07355.x.
  66. ^ a b c Cockell, Charles S. (2007). "The Interplanetary Exchange of Photosynthesis". Origins of Life and Evolution of Biospheres. 38 (1): 87–104. Bibcode:2008OLEB...38...87C. doi:10.1007/s11084-007-9112-3. PMID 17906941. S2CID 5720456.
  67. ^ Horneck, Gerda; Stöffler, Dieter; Ott, Sieglinde; et al. (2008). "Microbial Rock Inhabitants Survive Hypervelocity Impacts on Mars-Like Host Planets: First Phase of Lithopanspermia Experimentally Tested". Astrobiology. 8 (1): 17–44. Bibcode:2008AsBio...8...17H. doi:10.1089/ast.2007.0134. PMID 18237257.
  68. ^ Fajardo-Cavazos, Patricia; Link, Lindsey; Melosh, H. Jay; Nicholson, Wayne L. (2005). "Bacillus subtilis Spores on Artificial Meteorites Survive Hypervelocity Atmospheric Entry: Implications for Lithopanspermia". Astrobiology. 5 (6): 726–736. Bibcode:2005AsBio...5..726F. doi:10.1089/ast.2005.5.726. PMID 16379527.
  69. ^ Cockell, Charles S.; Brack, André; Wynn-Williams, David D.; Baglioni, Pietro; et al. (2007). "Interplanetary Transfer of Photosynthesis: An Experimental Demonstration of a Selective Dispersal Filter in Planetary Island Biogeography". Astrobiology. 7 (1): 1–9. Bibcode:2007AsBio...7....1C. doi:10.1089/ast.2006.0038. PMID 17407400.
  70. ^ "Could Life Have Survived a Fall to Earth?". EPSC. 12 September 2013. Retrieved 2015-04-21.
  71. ^ Boyle, Rebecca (2017-05-16). "Microbes might thrive after crash-landing on board a meteorite". New Scientist. Retrieved 2019-12-11.
  72. ^ Mautner, Michael N. (2000). Seeding the Universe with Life: Securing Our Cosmological Future (PDF). Washington, DC. ISBN 978-0476003309.{{cite book}}: CS1 maint: location missing publisher (link)
  73. ^ Mautner, M; Matloff, G. (1979). "Directed panspermia: A technical evaluation of seeding nearby planetary systems" (PDF). Journal of the British Interplanetary Society. 32: 419. Bibcode:1979JBIS...32..419M.
  74. ^ Mautner, M. N. (1997). "Directed panspermia. 3. Strategies and motivation for seeding star-forming clouds" (PDF). Journal of the British Interplanetary Society. 50: 93–102. Bibcode:1997JBIS...50...93M.
  75. ^ "Impacts 'more likely' to have spread life from Earth". BBC. 23 August 2011. Retrieved 24 August 2011.
  76. ^ Orgel, Leslie E.; Crick, Francis H. (January 1993). "Anticipating an RNA world. Some past speculations on the origin of life: where are they today?". The FASEB Journal. 7 (1): 238–239. doi:10.1096/fasebj.7.1.7678564. PMID 7678564. S2CID 11314345.
  77. ^ Gold, Thomas (May 1960). "Cosmic Garbage". Air Force and Space Digest. 43 (5): 65.
  78. ^ Marx, G. (1979). "Message through time". Acta Astronautica. 6 (1–2): 221–225. Bibcode:1979AcAau...6..221M. doi:10.1016/0094-5765(79)90158-9.
  79. ^ Yokoo, H.; Oshima, T. (1979). "Is bacteriophage φX174 DNA a message from an extraterrestrial intelligence?". Icarus. 38 (1): 148–153. Bibcode:1979Icar...38..148Y. doi:10.1016/0019-1035(79)90094-0.
  80. ^ Overbye, Dennis (26 June 2007). "Human DNA, the Ultimate Spot for Secret Messages (Are Some There Now?)". The New York Times. Retrieved 2014-10-09.
  81. ^ Davies, Paul C.W. (2010). The Eerie Silence: Renewing Our Search for Alien Intelligence. Boston: Houghton Mifflin Harcourt. ISBN 978-0547133249.[page needed]
  82. ^ Anders, E.; Dufresne, E. R.; Hayatsu, R.; Cavaille, A.; Dufresne, A.; Fitch, F. W. (1964). "Contaminated Meteorite". Science. 146 (3648): 1157–1161. Bibcode:1964Sci...146.1157A. doi:10.1126/science.146.3648.1157. PMID 17832241. S2CID 38428960.

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