To fully understand what Viking may have missed and what it really told us
about the Mars surface, we'll need to look more closely at the experiments done.
There were two missions, Viking 1 and Viking 2, leaving Cape Canaveral, FL on August and September, in 1975. Each consisted of an orbiter and a lander. The orbiters studied the Mars atmosphere and surveyed the land. It also relayed information between Earth and Mars and found a suitable site for the landers. All equipment worked as designed.
The two landers set down on near opposite sides of Mars. Each did similar experiments on the surface. The most important experiments to search for life were: