Based on the Viking tests, astronomers concluded that there probably was no life on Mars. Begley (2006) documents the recent research showing that applying the Viking tests to earth, results in the conclusion that there is no life on earth, either. Once again, Feynman was way ahead of his time:
(p. 204) We like to sit down and talk about how different things could be from what we expected; take the Viking landers on Mars, for example, we were trying to think how many ways there could be life that they couldn’t find with that equipment.
Feynman, Richard P. The Pleasure of Finding Things Out: The Best Short Works of Richard P. Feynman. New York: Perseus Books, 1999.
(Note: italics in original.)
The reference on the Begley article:
Begley, Sharon. "Science Journal; Scientists Revisit Data on Mars with Minds More Open to ‘Life’." The Wall Street Journal (Fri., October 27, 2006): B1.