Viking Mission Experiments
Viking performed four major experiments on Mars.
The first was the Gas Chromatograph – Mass Spectrometer experiment in which a device (GCMS) chemically separated vapor components of the Martian soil and read the molecular weight of each chemical in a mass spectrometer. The result showed even less carbon in the soil than was present on the moon.
The Gas Exchange (GEX) experiment replaced the Martian atmosphere in a soil sample with helium in an incubation chamber. Over time the samples were tested to measure the concentrations of the gases. This was designed to see if some form of life was metabolizing the gases.
In the third experiment, known as Labeled Release (LR), a sample of soil was given a drop of nutrient solution containing a radioactive carbon. The experiment monitored the soil to see if the carbon was metabolized. On the first attempt at this experiment, there was immediate results in the form of radioactive gases. However, each subsequent experiment proved inconclusive.
The Pyrolytic Release experiment was designed to be a test of each of the preceding experiments upon success. As none of the others were successful, this one was conducted on its own. A simulated Martian atmosphere, again with radioactive carbon, was created. A soil sample was exposed to the atmosphere, light and water with the goal of identifying photosynthetic organisms. After a period of incubation over several days, the sample was heated to remove the gases and test for radioactivity in the biomass. Again, this experiment showed no results.