Editing Viking 1 (section)

=== Search for life ===
''Viking 1'' carried a biology experiment whose purpose was to look for evidence of life.  The [[Viking lander biological experiments]] weighed 15.5&nbsp;kg (34&nbsp;lbs) and consisted of three subsystems: the [[Viking lander biological experiments#Pyrolytic release|pyrolytic release]] experiment (PR), the labeled release experiment (LR), and the gas exchange experiment (GEX). In addition, independent of the biology experiments, Viking carried a gas chromatograph-mass spectrometer that could measure the composition and abundance of organic compounds in the Martian soil.<ref>{{Cite web|url=http://www.msss.com/http/ps/life/life.html|archive-url=https://web.archive.org/web/20141020034248/http://www.msss.com/http/ps/life/life.html|url-status=dead|title=Life on Mars|archive-date=October 20, 2014|website=www.msss.com}}</ref>  The results were surprising and interesting: the spectrometer gave a negative result; the PR gave a negative result, the GEX gave a negative result, and the LR gave a positive result.<ref>[http://www.spacedaily.com/news/mars-life-00g.html Viking Data May Hide New Evidence For Life.] Barry E. DiGregorio, July 16, 2000.</ref>  Viking scientist Patricia Straat stated in 2009, "Our [LR] experiment was a definite positive response for life, but a lot of people have claimed that it was a false positive for a variety of reasons."<ref>[http://dsc.discovery.com/news/2009/09/28/viking-lander-mars.html Viking 2 Likely Came Close to Finding H2O.] {{webarchive |url=https://web.archive.org/web/20090930025048/http://dsc.discovery.com/news/2009/09/28/viking-lander-mars.html |date=September 30, 2009 }} Irene Klotz, Discovery News, September 28, 2009.</ref>  Most scientists now believe that the data were due to inorganic chemical reactions of the soil; however, this view may be changing after the recent discovery of near-surface ice near the ''Viking'' landing zone.<ref>{{cite journal|last1=Stuurman|first1=C.M.|last2=Osinski|first2=G.R.|last3=Holt|first3=J.W.|last4=Levy|first4=J.S.|last5=Brothers|first5=T.C.|last6=Kerrigan|first6=M.|last7=Campbell|first7=B.A.|title=SHARAD detection and characterization of subsurface water ice deposits in Utopia Planitia, Mars|journal=Geophysical Research Letters|date=September 28, 2016|volume=43|issue=18|pages=9484–9491|doi=10.1002/2016gl070138|bibcode=2016GeoRL..43.9484S|doi-access=free}}</ref>  Some scientists still believe the results were due to living reactions.  No organic chemicals were found in the soil.  However, dry areas of [[Antarctica]] do not have detectable organic compounds either, but they have organisms living in the rocks.<ref>Friedmann, E.  1982.  Endolithic Microorganisms in the Antarctic Cold Desert.  Science: 215. 1045–1052.</ref>  Mars has almost no ozone layer, unlike the Earth, so UV light sterilizes the surface and produces highly reactive chemicals such as peroxides that would oxidize any organic chemicals.<ref>Hartmann, W.  2003.  ''A Traveler's Guide to Mars''.  Workman Publishing.  NY NY.</ref>  The [[Phoenix Lander|''Phoenix'' Lander]] discovered the chemical [[perchlorate]] in the Martian soil. Perchlorate is a strong oxidant so it may have destroyed any organic matter on the surface.<ref>[http://www.planetary.org/news/2008/0806_Alien_Rumors_Quelled_as_NASA_Announces.html Alien Rumors Quelled as NASA Announces Phoenix Perchlorate Discovery.] {{webarchive |url=https://web.archive.org/web/20100904132551/http://www.planetary.org/news/2008/0806_Alien_Rumors_Quelled_as_NASA_Announces.html |date=September 4, 2010 }} A.J.S. Rayl, August 6, 2008.</ref> If it is widespread on Mars, [[carbon-based life]] would be difficult at the soil surface.