Just saw this on Bautforum.com:

Viking landers may have missed Martian life.
22:19 23 October 2006
NewScientist.com news service
Mark Buchanan and David L Chandler
"Now, a paper by Rafael Navarro-Gonzalez of the University of Mexico and others demonstrates that the GCMS instrument was incapable of detecting organic compounds even in Mars-like soils from various locations on Earth. This includes Chile's Atacama desert, where other tests prove that living microbes are indeed present.
In some soils – including samples taken from Rio Tinto in Spain, which contain iron compounds similar to those detected in Mars soils by NASA's rover Opportunity, the sensitivity of the GCMS was actually a million times lower than its claimed threshold for detection."
http://www.newscientistspace.com/article.ns?id=dn10361&feedId=online-news_rss20

Bob Clark