Life on Mars - Viking Revisited
by Lee Pullen
for Astrobiology Magazine
Moffett Field CA (SPX) Nov 27, 2007
Mars is often suggested as a good location to search for alien life. Despite many missions to the red planet, it's still a mystery whether life existed there in the distant past or if it is thriving there today. Attempting to answer this question was an aim of the Viking missions of 1976, but the results of those experiments were frustratingly ambiguous.
http://www.marsdaily.com/reports/Life_on_Mars___Viking_Revisited_999.html