Post-Viking Biological Investigations of Mars (1977) / Chapter Skim
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SUMMARY OF VIKING FINDINGS RELEVANT TO MARTIAN BIOLOGY
SUMMARY OF VIKING FINDINGS RELEVANT TO MARTIAN BIOLOGY
Pages 3-11
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From page 3... ...
The relative humidity at the surface is unknown except in the North Polar region where orbital observations and calculations indicate saturation.4 2. The residual North Polar cap has been shown to be water ice, probably 1 to 1000 m or more thick.4'5 3.
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From page 4... ...
on Viking has detected 0.1 to 1.0 percent (w/w) water in regolith samples heated to 350°C or 500°C, but with one exception much less than 0.1 percent water in samples heated to 200°C.8 The results are consistent with the water being that in mineral hydrates of moderate thermal stability (perhaps hydrates of MgSO43)
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From page 5... ...
Liquid water adsorbed to the soil ought to have been detectable in the 200°C pyrolysis in the GCMS, but less than 0.1 percent was detected (several tenths percent in the subrock sample) , and that could represent mineral hydrate water of moderate or low thermal stability.8 The detailed measurements of surface temperatures and atmospheric pressures continue to preclude the existence of pure bulk water under equilibrium conditions.
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From page 6... ...
Instruments with the same characteristics as the flight instrument have invariably detected organic compounds in all terrestrial soil samples tested, including antarctic soils with few living organisms. The concentrations of organics, if present in Martian samples, appear less than the concentration of organics in lunar samples.13 The concentrations are less than those expected from the influx of carbonaceous chondrites (assuming the regolith is mixed to a depth of 100 m or less8)
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From page 7... ...
Thus, the ratio of organic carbon in living microorganisms to that in humus is about 1 percent, and the ratio of organic carbon in living microorganisms to the total organic and elemental carbon in oil, gas, coal, oil shale, humus, and in the oceans is estimated to be 0.0001 percent to 0.001 percent.2''6 If Martian surface samples in fact contain living microbes, one must assume that mechanisms exist which permit their existence, while at the same time preventing the buildup of their organic detritus to levels detectable in the GCMS. There are possibilities such as (a)
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From page 8... ...
In the LR experiment, the production of 14CO2 when regolith samples were initially moistened with a nutrient medium is consistent with biological activity.17 So also is the synthesis in the PR experiment of picomole quantities of organic matter during the 120-h incubation of samples in the light.15 (However, although statistically significant, the amount synthesized in the PR experiment is only about one-tenth that synthesized by terrestrial soils that give the minimal observed response, i.e., antarctic soils.18'19) In both the LR and PR experiments, the activity was abolished or appreciably reduced when the regolith samples were preheated to 170°C to 180°C for 3 h.
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From page 9... ...
Wydeven and his colleagues203 have also obtained oxygen evolution in amounts and at a rate comparable to that observed in GEX on Mars by exposing soil samples in a GEX experiment on Earth to a gas mixture obtained by passage of oxygen through a radio frequency glow discharge. The RF treatment produces active species of oxygen similar to those expected to be generated at the Martian surface by solar uv radiation.
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From page 10... ...
is to emphasize that conditions at the regolith-atmosphere interface on Mars are vastly different from those at the soil-atmosphere interface on Earth. This vast and incompletely characterized difference makes it inordinately difficult to conclude that experimental results, which are unambiguously ascribable to biological activity on Earth, are unambiguously ascribable to biological activity on Mars.
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From page 11... ...
the ability to account, at least qualitatively, for the results of GEX and LR by nonbiological reactions; (5) the prior demonstration that abiological organic synthesis can occur under conditions analogous to those in the p R experiment except for the wavelength of the incident radiation; and (6)
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