re:The original article explains it, Barry. Much better...
Barry wrote this in his article in IEEE which he hasn't figured out how to make an active link to: "...On board both Viking landers were miniature life detection laboratories, and some of the data they returned could indeed be interpreted as evidence for life on Mars. Yet the majority of the project's scientists became convinced that inorganic oxidants in the soil were responsible for the ambiguous data. The next year, NASA publicly announced its conclusion: that Viking had found no life..."
Well read this article and it explains how they came to these conclusions.
--Chris Vancil