Viking gas exchange (GEX) experiment
One of the the three main biological experiments carried aboard each Viking
lander; GEX was developed by Vance Oyama at
NASA Ames Research Center and designed to test for life under two different
conditions. In the first mode, it was assumed that organisms that had been
dormant for a very long time under dry conditions on Mars
would be revived and stimulated back into metabolic activity by the addition
of moisture alone. The effect of any subsequent Martian life processes would
be to alter the composition of the gases (such as carbon dioxide, nitrogen,
and methane) above the sample in a way that would be measurable by the onboard
gas chromatograph. During a 10-day incubation period, the gas composition
was determined five times. In the second, wet nutrient (or "chicken soup")
mode, a rich organic broth (containing 19 amino acids, vitamins, a number
of other organic compounds, and a few inorganic salts) was "fed" to the
sample as a further encouragement to induce metabolism. Again, a change
in the gas mixture might indicate that some kind of organism was stirring
into life.
Related entry
• Viking's
search for life on Mars
Related categories
• MARS
TOPICS
• ASTROBIOLOGY
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