Carbon Assimilation
This experiment was designed to test for Martian organisms which would
utilize CO2 or CO. The lander brought with it
specially 'tagged'
Carbon, having a unique isotopic ratio. They exposed the soil, both with
and without water, to see if anything took in the tagged Carbon.
Later the soil sample was heated to release any organics created.
Tagged Carbon was taken up by the soil! However, at very low levels.
Further tests at much higher temperatures gave a continued positive
response, long after biota would have been killed. The tagged Carbon
was being taken in to form carbonate minerals or polymers in the soil,
but not by organisms. Conclusion: Probably No Life
Release Experiment
In this test, specially tagged (again with a unique isotopic ratio)
organic materials (i.e. nutrients) were introduced into the soil,
such as lactate, glucose, etc., in water. Included were both
right-handed and left-handed sugars! If the organisms `ate'
the nutrients, they would expel waste gases containing the tagged
isotopic species. Scientists saw an increasing level of
this tagged gas (as the organisms ate the nutrients), leveling off (as
as the nutrients were `used up'). Furthermore, heating the sample
reduced the signal, and when it reached 160C the signal was lost
(killing the organisms). This was precisely the
signal behavior expected from biological organisms! However,
it could also be explained by chemical reactions (oxidation, etc).
Conclusion: Maybe Life
Gas Exchange Experiment
Again, the soil was exposed to a mixture of nutrients (amino acids,
salts, vitamins, etc), then the gas was continually sampled for
changing levels in H2, CH4, etc. This
experiment was run in both wet and humid mode. Oxygen was given off
as soon as the soil was exposed! However.. again, this could have
been due to oxidation reactions (non-biological activity).
Conclusion: Probably No Life
Interestingly enough, all three biological experiments showed positive results, as expected for biological life. However, all three results were also inconclusive because each result could also be explained by non-biological activity. Sounds like some poorly designed experiments, if they get their predicted results and still can't determine if life exists!