(05.06.2008) it was back in 1969 when two scientists from the University of California at Berkeley, Dr. George C. Pimentel and Dr. Kenneth Herr, announced the discovery of methane and ammonia in the Martian atmosphere using Mariner 7 data.
Guess what: that report was withdrawn one month later due to “the possibililty of misinterpretation of the absorption of similar specral bands by frozen carbon dioxide”, blabla.