Post-Viking Biological Investigations of Mars (1977) / Chapter Skim
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POST-VIKING BIOLOGY STRATEGY FOR MARS
POST-VIKING BIOLOGY STRATEGY FOR MARS
Pages 12-22
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From page 12... ...
It is remarkable, then, that on Mars no carbon has been detected definitively except in the atmosphere and in the winter polar caps, and none has been detected in a form more reduced than CO. The detection of reduced carbon would not prove current or past life (since it could be deposited by carbonaceous chondrites 12
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From page 13... ...
Biological activity modifies the composition of the surrounding gases. The detection of disequilibria between the bulk atmosphere and the occluded gases in a soil sample would not prove the presence of life, but soil samples exhibiting prolonged disequilibria of changing magnitude would certainly be deemed more likely to contain active organisms.
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From page 14... ...
On the other hand, if the results of the current pyrolytic release experiment represent abiogenic organic synthesis, there may be sufficient steady-state quantities of organic compounds below the Martian surface to support heterotrophy or chemical autotrophy. In summary, then, from the biological viewpoint, the prime concern for the next mission to Mars should be exploration of the subsurface in favorable areas containing sediments or layered sequences such as alluvial flows, the margins of polar ice caps, and terrain likely to overlay permafrost.
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From page 15... ...
Instruments. Instruments of the requisite type, sensitivity, and resolution either have flown on the current Viking or appear adaptable to future soft landers without difficulty.
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From page 16... ...
A tremendous gap exists between the topographical features that are resolved and interpretable at orbital altitudes and the surface features that are actually found by landers. It is quite conceivable that a site chosen from orbit for highly interesting topographical features such as fluvial activity would upon landing appear indistinguishable from the VL-1 and VL-2 sites, both at the landing site and for a hundred kilometers around.
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From page 17... ...
If initiated without the prior information, should the delivery mode be penetrators which could sample at uncontrollable depths down to several meters, or should the delivery mode be a mobile soft lander provided at major additional cost with the ability to sample at controllable sites to controllable depths of perhaps several meters?
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From page 18... ...
A soft lander can unquestionably carry the necessary instrumentation to characterize subsurface samples, but there are serious questions as to whether it can reach the areas that are prime candidates for sampling; (2) hard landers can probably reach the areas that are prime candidates for sampling, but there are unresolved questions as to whether *
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From page 19... ...
Whether the samples are characterized by a soft lander or hard lander, the extent to which they possess reduced carbon, water, soluble electrolytes, gas disequilibria, and 13 Cand 3* S depletion should determine the priority accorded to the initiation of a subsequent phase in the biological exploration of Mars, namely, a detailed examination of samples for direct evidence of current or former life.
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From page 20... ...
Furthermore, of necessity, most metabolic experiments tend to be highly geocentric. Thus two of the three current Viking experiments are in fact terrestrial microbial experiments in which soil samples are exposed to terrestrially oriented organic substrates under terrestrial conditions of temperature and water.
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From page 21... ...
Since Martian samples will have been exposed daily to temperatures below 220°K and will have been exposed annually to temperatures as low as 149°K, it is likely that they could be cooled to and maintained at <120°K without significant alteration, temperatures which preclude nearly all thermally driven chemical reactions. These conclusions about the high scientific potential of returning unsterilized Martian samples to Earth reaffirm existing Space Science Board policy1' p'19 and are consistent with the conclusions of several publications, internal reports, and workshops.32"35 The matter of the physical containment of returned unsterilized samples has also been analyzed by these same and other groups.
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From page 22... ...
,4 minimum of one mission then would have to be devoted to the first characterization phase. If the decision based on that first phase were positive, our strategy would dictate that the next mission initiate the detailed biological study, and that it be a Mars Sample Return (MSR)
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