One of
the surest methods of preserving bacteria indefinitely is to freeze-dry
(lyophilize) them under conditions similar to those on Mars. Recovery from
the resting cell state can be extremely rapid. An Oscillatoria
strain subjected to drying in a desiccator above silica gel showed
instantaneous recovery of photosynthesis upon resuscitation, with 100
percent viability.73
During the development of the Mars Oxidant Experiment
(MOx)74, a test75 was conducted in which a
California soil was dried to constant weight at 70░C. The end of an
optical fiber was dipped into a glucose solution and dried, then was put
into the dried soil and monitored for changes in reflectivity of the
coated end to laser pulses sent through it as evidence for reaction. FIG.
5 shows the very rapid response showing that the glucose was being
removed. A separate portion of the same soil pre-heated to 130░C produced
no change in reflectivity confirming that the glucose had been removed by
microorganisms. (A duplicate glucose-coated fiber put into solid potassium
superoxide produced no reaction.) These results are reminiscent of the
Viking LR data. The possibility exists that martian organisms may
metabolize under present conditions or, long dormant, may have been
resuscitated by the LR experiment.
4. "Too Much Too Soon": When the first positive
result from the LR was obtained, it was stated that the response was "too
much too soon" for microorganisms living under the extreme conditions of
Mars. The Mars response was erroneously portrayed as exceeding the LR
responses obtained from terrestrial soils and, therefore, indicative of
chemistry. Were microorganisms present on Mars, the reasoning ran, they
would be in far lesser numbers than in terrestrial soils. Hence, their
response would be less, especially considering the harsh Mars environment.
Furthermore, it was said that the response kinetics were indicative of
chemistry, not biology. FIG. 6 compiles data directly comparing LR
responses from a variety of terrestrial soils to the VL1 positive LR Mars
response. The LR Mars response is seen to be near the lower end of the
range, close to the Antarctic responses and to that from the Aiken soil in
an LR flight instrument sealed within a chamber under the martian
experiment conditions. The kinetics are seen to be similar. Thus, the "too
much too soon" reason against acceptance of the LR response as biological
is not supported by the relevant data.
5. 2nd Injection: LR tests with terrestrial
soils generally show that, after a plateau in gas evolution has been
reached, a second injection of the labeled nutrient produces a sharp
renewal in gas evolution. While this was not one of the criteria for a
determination of life on Mars, it would have lent support to such a
determination. As seen in FIG. 7, when a second injection of nutrient was
applied following the standard eight-day test cycle on Mars, approximately
20% of the gas previously evolved disappeared from the headspace of the
instrument. This happened at both Viking sites. The gas slowly re-evolved
to its eight-day level after approximately two months. A recent
publication76 cites the lack of a vigorous evolution of gas
following the second injection as the reason the LR results could not be
from microorganisms. The second injection results seem to be the simple
reabsorption of gas by the soil when wetted. In a laboratory
simulation77, a Viking-type LR instrument containing sterilized
Mars analog soil reproduced the reabsorption of approximately 20% of the
headspace gas, FIG. 7 (shown with FIG. 1 for comparison). Furthermore, a
search of the Viking development files revealed active soils which
demonstrated the same lack of response, or slight reabsorption of gas,
upon a second injection. Apparently, the microorganisms died during the
test and the addition of water promoted reabsorption of the CO2
evolved after the first injection.
