Viking lander biological experiments: Difference between revisions

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In short, the findings are intriguing but there is no consensus yet on whether the correct interpretation is biological or chemical. Most scientists still favour the chemical explanation, though a few scientists have recently shown renewed interest in a possible biological explanation.
 
== Critiques ==
[[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.<ref>{{cite web |url=http://archive.salon.com/people/feature/2000/08/17/lovelock/ |title=James Lovelock, Gaia's grand old man |last=Joseph |first=Lawrence E. |date=2000-08-17 |publisher=Salon |accessdate=2009-02-10 |deadurl=yes |archiveurl=https://web.archive.org/web/20090408145043/http://archive.salon.com/people/feature/2000/08/17/lovelock/ |archivedate=2009-04-08 |df= }}</ref> He concluded that there was enough information about Mars' atmosphere at that time to discount the possibility of life there. Since then, [[Atmosphere of Mars#Methane|methane has been discovered in Mars]]' atmosphere at 10ppb, thus reopening this debate. Although [[Climate of Mars#Methane presence|in 2013 the Curiosity rover failed to detect methane]] at its location in levels exceeding 1.3ppb.<ref name="SJ-20130919">{{cite journal |last=Webster |first=Christopher R. |last2=Mahaffy |first2=Paul R. |last3=Atreya |first3=Sushil K. |last4=Flesch |first4=Gregory J. |last5=Farley |first5=Kenneth A. |title=Low Upper Limit to Methane Abundance on Mars |url=http://www.sciencemag.org/content/early/2013/09/18/science.1242902.abstract |date=2013-09-13 |journal=[[Science (journal)|Science]] |doi=10.1126/science.1242902 |accessdate=2013-09-19 |volume=342 |issue=6156 |pages=355–357|bibcode = 2013Sci...342..355W |pmid=24051245}}</ref> later in 2013 and in 2014, measurements by Curiosity did detect methane,<ref>NASA, [https://science.nasa.gov/science-news/science-at-nasa/2014/16dec_methanespike Curiosity Detects Methane Spike on Mars], Dec. 16, 2014 (accessed 25 Oct. 2016)</ref> 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.<ref>{{cite news |first=Paul |last=Rincon |title=Agencies outline Mars initiative |date=2009-07-09 |publisher=BBC |url=http://news.bbc.co.uk/2/hi/science/nature/8130393.stm |work=BBC News |accessdate=2009-07-26 }}</ref><ref>{{cite news |title=NASA orbiter to hunt for source of Martian methane in 2016 |date=2009-03-06 |url=http://www.thaindian.com/newsportal/health/nasa-orbiter-to-hunt-for-source-of-martian-methane-in-2016_100163335.html |work=Thaindian News |accessdate=2009-07-26 }}</ref> 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.<ref name="viking killers">{{cite web |title=Did probes find Martian life ... or kill it off? |url=http://www.msnbc.msn.com/id/16516952/ |last=Borenstein |first=Seth |publisher=Associated Press via MSNBC |date=2007-01-07 |accessdate=2007-05-31 }}</ref> 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 Rover]]s each used this landing technique successfully. The [[Phoenix (spacecraft)|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.
 
== Future missions ==
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* [[Viking 2]]
*[[Europa Lander (NASA)]] (The next NASA mission with primary science life detection)
*[[Gillevinia straata]]
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