Talk:Viking lander biological experiments

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Old controversy section[edit source | hide | hide all]

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.[1] This view has been put forward by the designer of the LR experiment, Gilbert Levin, who believes the positive LR results are diagnostic for life on Mars.[2] He and others have conducted ongoing experiments attempting to reproduce the Viking data, either with biological or non-biological materials on Earth.

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.[3][4][5] On 2006, scientist Rafael Navarro demonstrated that the Viking biological experiments likely lacked sensitivity to detect trace amounts of organic compounds.[6] In a paper published in December 2010,[7] 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 biosignatures in the future.[8][9] Results from the current Mars Science Laboratory mission and the under-development ExoMars program, may help settle this controversy.[9]

Critiques[edit source | hide]

James Lovelock 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 not in chemical equilibrium.[10] He concluded that there was enough information about Mars' atmosphere at that time to discount the possibility of life there. Since then, methane has been discovered in Mars' atmosphere at 10ppb, thus reopening this debate. Although in 2013 the Curiosity rover failed to detect methane at its location in levels exceeding 1.3ppb.[11] later in 2013 and in 2014, measurements by Curiosity did detect methane,[12] suggesting a time-variable source. The planned ExoMars Trace Gas Orbiter, launched on March 2016, will implement 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.[13][14] The Mars Orbiter Mission is also 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.[15] That is not a problem for missions which land via an airbag-protected capsule, slowed by parachutes and retrorockets, and dropped from a height that allows rocket exhaust to avoid the surface. Mars Pathfinder's Sojourner rover and the Mars Exploration Rovers each used this landing technique successfully. The Phoenix Scout lander descended to the surface with retro-rockets, however, their fuel was hydrazine, and the end products of the plume (water, nitrogen, and ammonia) were not found to have affected the soils at the landing site.
  1. Cite error: Invalid <ref> tag; no text was provided for refs named Chambers
  2. Spie (2014). "Gilbert Levin: Mars microbes -- proof from the Viking missions?". SPIE Newsroom. doi:10.1117/2.3201403.03. 
  3. Levin, Gilbert (2007). "Analysis of evidence of Mars life". Electroneurobiología. 15 (2): 39–47. ISSN 1850-1826. 
  4. Navarro-González, Rafael; Navarro, Karina F.; de la Rosa, José; Iñiguez, Enrique; Molina, Paola; Miranda, Luis D.; Morales, Pedro; Cienfuegos, Edith; Coll, Patrice; Raulin, François; Amils, Ricardo; McKay, Christopher P. (2006). "The limitations on organic detection in Mars-like soils by thermal volatilization-gas chromatography-MS and their implications for the Viking results". Proceedings of the National Academy of Sciences of the United States of America. 103 (44): 16089–16094. Bibcode:2006PNAS..10316089N. doi:10.1073/pnas.0604210103. PMC 1621051Freely accessible. PMID 17060639. 
  5. Paepe, Ronald (2007). "The Red Soil on Mars as a proof for water and vegetation" (PDF). Geophysical Research Abstracts. 9 (1794). Retrieved 2008-08-14. 
  6. Navarro-González, Rafael; Navarro, Karina F.; de la Rosa, José; Iñiguez, Enrique; Molina, Paola; Miranda, Luis D.; Morales, Pedro; Cienfuegos, Edith; Coll, Patrice; Raulin, François; Amils, Ricardo; McKay, Christopher P. (2006). "The limitations on organic detection in Mars-like soils by thermal volatilization–gas chromatography–MS and their implications for the Viking results". Proc. Natl. Acad. Sci. 103 (44): 16089–16094. Bibcode:2006PNAS..10316089N. doi:10.1073/pnas.0604210103. PMC 1621051Freely accessible. PMID 17060639. 
  7. Cite error: Invalid <ref> tag; no text was provided for refs named reanalysis
  8. Cite error: Invalid <ref> tag; no text was provided for refs named Webster
  9. 9.09.1 Wall, Mike (2011-01-06). "Life's Building Blocks May Have Been Found on Mars, Research Finds". Space.com. Archived from the original on 2011-01-09. Retrieved 2011-01-07. 
  10. Joseph, Lawrence E. (2000-08-17). "James Lovelock, Gaia's grand old man". Salon. Archived from the original on 2009-04-08. Retrieved 2009-02-10. 
  11. Webster, Christopher R.; Mahaffy, Paul R.; Atreya, Sushil K.; Flesch, Gregory J.; Farley, Kenneth A. (2013-09-13). "Low Upper Limit to Methane Abundance on Mars". Science. 342 (6156): 355–357. Bibcode:2013Sci...342..355W. doi:10.1126/science.1242902. PMID 24051245. Retrieved 2013-09-19. 
  12. NASA, Curiosity Detects Methane Spike on Mars, Dec. 16, 2014 (accessed 25 Oct. 2016)
  13. Rincon, Paul (2009-07-09). "Agencies outline Mars initiative". BBC News. BBC. Retrieved 2009-07-26. 
  14. "NASA orbiter to hunt for source of Martian methane in 2016". Thaindian News. 2009-03-06. Retrieved 2009-07-26. 
  15. Borenstein, Seth (2007-01-07). "Did probes find Martian life ... or kill it off?". Associated Press via MSNBC. Retrieved 2007-05-31.