Editing Viking lander biological experiments (section)

=== Gas exchange ===
The gas exchange ('''GEX''') experiment (PI: [[Vance Oyama]], NASA Ames) looked for gases given off by an incubated soil sample by first replacing the Martian atmosphere with the inert gas [[helium]].  It applied a liquid complex of organic and inorganic nutrients and supplements to a soil sample, first with just nutrients added, then with water added too.<ref name="Chambers" /> Periodically, the instrument sampled the atmosphere of the incubation chamber and used a [[gas chromatograph]] to measure the concentrations of several gases, including [[oxygen]], CO<sub>2</sub>, [[nitrogen]], [[hydrogen]], and [[methane]].  The scientists hypothesized that metabolizing organisms would either consume or release at least one of the gases being measured.

In early November 1976, it was reported that "on Viking 2, the gas exchange experiment is producing analogous results to those from Viking 1. Again, oxygen disappeared once the nutrient solution came into contact with the soil. Again, carbon dioxide began to appear and still continues to evolve".<ref>{{Cite web | url=https://books.google.com/books?id=JqEhtUjqORIC&pg=PA272 |title = New Scientist| publisher = Reed Business Information|date = 1976-11-04|last1=Burgess|first1=Eric}}</ref>