The Viking Labeled Release Experiment and Life on Mars

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.

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