MARS - Viking: Lab - Exploring The Planets.
"Although Viking life experiments were inconclusive, the search for ancient organisms remains a primary research objective for future spacecraft exploration of Mars. The search for life on Mars was highlighted recently in a study which found what may be ancient organic material in a Mars meteorite (SNC) that was found on Earth."
http://www.nasm.si.edu/research/ceps/etp/mars/viking_lab.html#life

2002-09-05 | MISSIONS
No Place for Life to Hide from Mars Express
"ESA's Mars Express mission is the first attempt to look for direct and indirect evidence of life on the surface of Mars since NASA's Viking biological experiments in 1976. While the Viking mission returned valuable data, results of the biological experiments it performed where inconclusive—proving only that determining what factors constitute a biosignature is no easy task."
http://astrobiology.arc.nasa.gov/news/expandnews.cfm?id=9305

SP-4012 NASA HISTORICAL DATA BOOK: VOLUME III
PROGRAMS AND PROJECTS 1969-1978
CHAPTER THREE
SPACE SCIENCE
INTRODUCTION
"Launched by Titan-Centaur vehicles in the late summer of 1975, Viking I and 2 reached Mars in June and August 1976. The orbiters' high-resolution cameras found a younger, more dynamic planet than earlier Mariners has revealed, and the landing site certification team was forced to look for new safer sites for the two Viking landers. Viking I touched down on the Chryse Plains on July 20, 1976; Viking 2 landed on the Utopia Plains on September 3. The two landers immediately began sending a wealth of imagery and scientific data from the surface (see fig. 3-9), but they did not answer definitively the question of the existence of life on Mars. Biology experiments provided information on the chemical makeup of the samples taken and sensors gave scientists a look at the Martian environment, but the investigations were inconclusive. Scientists could not say that life did not or did exist at the end of the primary mission in November."
http://history.nasa.gov/SP-4012/vol3/ch3.htm

NASA Quest > Archives
"Chris McKay, an astrogeophysicist from NASA Ames described the importance of Mars as a subject of planetary exploration. Mars is interesting in part because its surface shows water channels and other evidence of having an early evolution as a planet similar to earth
"In 1976 the Viking spacecraft investigated the Martian surface. A claw was unilized to sample the surface and a mini-laboratory analyzed the soil for evidence of life. The results were inconclusive, but as Chris pointed out, we had reached across space to another planet and grasped out for understanding its importance as a harbinger of life. This critical event changed his life, and he has worked to understand life's origins here and in space."
http://quest.arc.nasa.gov/marsconf/look/7-18/

Bob Clark