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Pseudo-panspermia

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Pseudo-panspermia (sometimes called soft panspermia, molecular panspermia or quasi-panspermia) is a well-supported hypothesis for a stage in the origin of life. The theory first asserts that many of the small organic molecules used for life originated in space (for example, being incorporated in the solar nebula, from which the planets condensed). It continues that these organic molecules were distributed to planetary surfaces, where life then emerged on Earth and perhaps on other planets. Pseudo-panspermia differs from the fringe theory of panspermia, which asserts that life arrived on Earth from distant planets.[1]

Background

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Further information: Panspermia
Some stages in the origin of life are well-understood, such as the habitable Earth and the abiotic synthesis of simple molecules, whether in space or on Earth. Later stages remain more speculative.[2]

Theories of the origin of life have been recorded since the 5th century BC, when the Greek philosopher Anaxagoras proposed an initial version of panspermia: life arrived on earth from the heavens.[3] In modern times, full panspermia has little support amongst mainstream scientists.[1] Pseudo-panspermia, in which molecules are formed and transported through space is, however, well-supported.[2]

Extraterrestrial creation of organic molecules

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Interstellar molecules are formed by chemical reactions within very sparse interstellar or circumstellar clouds of dust and gas. Usually this occurs when a molecule becomes ionised, often as the result of an interaction with cosmic rays. This positively charged molecule then draws in a nearby reactant by electrostatic attraction of the neutral molecule's electrons. Molecules can also be generated by reactions between neutral atoms and molecules, although this process is generally slower.[4] The dust plays a critical role of shielding the molecules from the ionizing effect of ultraviolet radiation emitted by stars.[5] The Murchison meteorite contains the organic molecules uracil and xanthine,[6][7] which must therefore already have been present in the early Solar System, where they could have played a role in the origin of life.[8]

Nitriles, key molecular precursors of the RNA World scenario, are among the most abundant chemical families in the universe and have been found in molecular clouds in the center of the Milky Way, protostars of different masses, meteorites and comets, and also in the atmosphere of Titan, the largest moon of Saturn.[9][10]

Evidence for the extraterrestrial creation of organic molecules includes both their discovery in various contexts in space, and their laboratory synthesis under extraterrestrial conditions:

Extraterrestrial organic molecules found in space
Molecule Class Body Notes
Glycine Amino acid Comet NASA, 2009[11]
mixed aromatic-aliphatic compounds Cosmic dust 2011[12][13]
Glycolaldehyde Sugar-related Around a protostar Copenhagen University, 2012[14][15] Precursor of RNA[16]
Cyanomethanimine, Ethanimine Imines Icy particles in interstellar space Precursors of nucleobase adenine, and of amino acid alanine[17]
polycyclic aromatic hydrocarbons (PAHs) widespread, 20% of carbon in universe NASA, 2014[18]
Glycine,
Methylamine,
Ethylamine		 Amino acid, amines Coma of comet 67P/Churyumov-Gerasimenko Rosetta Mission, 2016[19]
Uracil, Niacin Nucleobase, vitamer 162173 Ryugu Hayabusa2, 2023[20][21]
Laboratory syntheses under extraterrestrial conditions
Molecule Class Conditions Notes
Precursors of amino acids and nucleotides Interstellar medium NASA, 2012, starting from polycyclic aromatic hydrocarbons (PAHs)[22][23]
Uracil,
Cytosine,
Thymine		 Nucleobases Pyrimidine, outer space NASA, 2015[24]
Oligoglycines Peptides Low-temperature areas of outer space Initial materials are CO, C, and NH3, common in molecular clouds of the interstellar medium[25][26]

Planetary distribution of organic molecules

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Organic molecules can then be distributed to planets including Earth both when the planets formed and later. If the materials from which planets formed contained organic molecules, and were not destroyed by heat or other processes, then these would be available for abiogenesis on those planets.

Later distribution is by means of bodies such as comets and asteroids. These may fall to the planetary surface as meteorites, releasing any molecules they are carrying as they vaporise on impact or later as they erode. Findings of organic molecules in meteorites include:

Organic molecules found in meteorites
Molecule Class Notes
Adenine,
Guanine		 Nucleobase NASA, 2011[27][28]
Sugars In "primitive meteorites"[29]
Guanine,
Adenine,
Cytosine,
Uracil,
Thymine		 Nucleobases 2022[30]


Large asteroids with ice and organic chemicals
Asteroid Location Notes
24 Themis Asteroid Belt NASA, Jet Propulsion Laboratory,
Near Earth Objects, life on Earth[31]
269 Justitia Asteroid Belt NASA, JPL Small-Body Database[32]

References

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  1. ^ a b May, Andrew (2019). Astrobiology: The Search for Life Elsewhere in the Universe. London: Icon Books. ISBN 978-1-78578-342-5. 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
  2. ^ a b Walker, Sara I.; Packard, N.; Cody, G. D. (13 November 2017). "Re-conceptualizing the origins of life". Philosophical Transactions of the Royal Society A. 375 (2109): 20160337. Bibcode:2017RSPTA.37560337W. doi:10.1098/rsta.2016.0337. PMC 5686397. PMID 29133439.
  3. ^ 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.
  4. ^ Dalgarno, A. (2006). "The galactic cosmic ray ionization rate". Proceedings of the National Academy of Sciences. 103 (33): 12269–73. Bibcode:2006PNAS..10312269D. doi:10.1073/pnas.0602117103. PMC 1567869. PMID 16894166.
  5. ^ Brown, Laurie M.; Pais, Abraham; Pippard, A. B. (1995). "The physics of the interstellar medium". Twentieth Century Physics (2nd ed.). CRC Press. p. 1765. ISBN 978-0-7503-0310-1.
  6. ^ Martins, Zita; Botta, Oliver; Fogel, Marilyn L.; Sephton, Mark A.; Glavin, Daniel P.; Watson, Jonathan S.; Dworkin, Jason P.; Schwartz, Alan W.; Ehrenfreund, Pascale (2008). "Extraterrestrial nucleobases in the Murchison meteorite". Earth and Planetary Science Letters. 270 (1–2): 130–36. arXiv:0806.2286. Bibcode:2008E&PSL.270..130M. doi:10.1016/j.epsl.2008.03.026. S2CID 14309508.
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  14. ^ Than, Ker (August 29, 2012). "Sugar Found In Space". National Geographic. Archived from the original on September 1, 2012. Retrieved August 31, 2012.
  15. ^ "Sweet! Astronomers spot sugar molecule near star". AP News. August 29, 2012. Retrieved August 31, 2012.
  16. ^ Jørgensen, Jes K.; Favre, Cécile; Bisschop, Suzanne E.; Bourke, Tyler L.; et al. (2012). "Detection of the Simplest Sugar, Glycolaldehyde, in a Solar-Type Protostar with Alma". The Astrophysical Journal. 757 (1): L4. arXiv:1208.5498. Bibcode:2012ApJ...757L...4J. doi:10.1088/2041-8205/757/1/L4. S2CID 14205612.
  17. ^ Loomis, Ryan A.; Zaleski, Daniel P.; Steber, Amanda L.; et al. (2013). "The Detection of Interstellar Ethanimine (CH3CHNH) from Observations Taken During the GBT PRIMOS Survey". The Astrophysical Journal. 765 (1): L9. arXiv:1302.1121. Bibcode:2013ApJ...765L...9L. doi:10.1088/2041-8205/765/1/L9. S2CID 118522676.
  18. ^ Hoover, Rachel (February 21, 2014). "Need to Track Organic Nano-Particles Across the Universe? NASA's Got an App for That". NASA. Retrieved 22 February 2014.
  19. ^ "Prebiotic chemicals – amino acid and phosphorus – in the coma of comet 67P/Churyumov-Gerasimenko".
  20. ^ Strickland, Ashley (2023-03-21). "RNA compound and vitamin B3 found in samples from near-Earth asteroid". CNN. Retrieved 2023-03-24.
  21. ^ Oba, Yasuhiro; Koga, Toshiki; Takano, Yoshinori; Ogawa, Nanako O.; Ohkouchi, Naohiko; Sasaki, Kazunori; Sato, Hajime; Glavin, Daniel P.; Dworkin, Jason P.; Naraoka, Hiroshi; Tachibana, Shogo; Yurimoto, Hisayoshi; Nakamura, Tomoki; Noguchi, Takaaki; Okazaki, Ryuji (2023-03-21). "Uracil in the carbonaceous asteroid (162173) Ryugu". Nature Communications. 14 (1): 1292. Bibcode:2023NatCo..14.1292O. doi:10.1038/s41467-023-36904-3. ISSN 2041-1723. PMC 10030641. PMID 36944653.
  22. ^ "NASA Cooks Up Icy Organics to Mimic Life's Origins". Space.com. September 20, 2012. Retrieved September 22, 2012.
  23. ^ Gudipati, Murthy S.; Yang, Rui (2012). "In-Situ Probing of Radiation-Induced Processing of Organics in Astrophysical Ice Analogs – Novel Laser Desorption Laser Ionization Time-Of-Flight Mass Spectroscopic Studies". The Astrophysical Journal. 756 (1): L24. Bibcode:2012ApJ...756L..24G. doi:10.1088/2041-8205/756/1/L24. S2CID 5541727.
  24. ^ Marlaire, Ruth (3 March 2015). "NASA Ames Reproduces the Building Blocks of Life in Laboratory". NASA. Retrieved 5 March 2015.
  25. ^ 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.
  26. ^ Krasnokutski, Serge A.; Jäger, Cornelia; Henning, Thomas; Geffroy, Claude; Remaury, Quentin B.; Poinot, Pauline (2024-04-19). "Formation of extraterrestrial peptides and their derivatives". Science Advances. 10 (16): eadj7179. arXiv:2405.00744. Bibcode:2024SciA...10J7179K. doi:10.1126/sciadv.adj7179. ISSN 2375-2548. PMC 11023503. PMID 38630826.
  27. ^ Callahan, M. P.; Smith, K. E.; Cleaves, H. J.; et al. (2011). "Carbonaceous meteorites contain a wide range of extraterrestrial nucleobases". Proceedings of the National Academy of Sciences. 108 (34): 13995–98. Bibcode:2011PNAS..10813995C. doi:10.1073/pnas.1106493108. PMC 3161613. PMID 21836052.
  28. ^ Steigerwald, John (8 August 2011). "NASA Researchers: DNA Building Blocks Can Be Made in Space". NASA. Retrieved 10 August 2011.
  29. ^ 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): 24440–45. Bibcode:2019PNAS..11624440F. doi:10.1073/pnas.1907169116. PMC 6900709. PMID 31740594.
  30. ^ Oba, Yasuhiro; et al. (26 April 2022). "Identifying the wide diversity of extraterrestrial purine and pyrimidine nucleobases in carbonaceous meteorites". Nature Communications. 13 (2008): 2008. Bibcode:2022NatCo..13.2008O. doi:10.1038/s41467-022-29612-x. PMC 9042847. PMID 35473908.
  31. ^ "Life On Earth". NASA-JPL. JPL. Retrieved 14 September 2022.
  32. ^ "NASA Open Data Portal". NASA dot gov. NASA. Retrieved 14 September 2022.
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