7. UV Light: This early hypothesis sought to explain both the LR active response and the lack of organics reported by the GCMS. An experiment at Viking Landing Site 2 eliminated this possibility. Before dawn, the sampling arm moved a rock before the sun’s rays could strike it. A sample of soil that had underlain the rock and thus was protected from UV for eons was taken and promptly delivered to the instrument. Despite the absence of any UV exposure, the sample produced a positive LR response, essentially identical in kinetics and in magnitude to those of the Viking Lander 1 positive response seen in FIG. 1. This direct experiment carried out on Mars eliminated the possibility that UV light was the cause of the activity detected by the LR experiment on Mars.
8. Clays: It was proposed84,85,86 that clays on Mars reacted with the LR nutrient to produce labeled CO2 . Various clays were proposed in sequence as experiments detected deficiencies in duplicating the LR results. The clays, in turn, ranged from montmorillonite to nontronite to palagonite to smectites. The experiments suffered from basic problems87 including the failure to sterilize the samples tested or to use sterile procedures in the experiment in order to exclude biological effects from microorganisms in the clays. Extreme pHs were imposed to obtain responses and the responses did not have the kinetics of the LR positive responses. Data replicating the thermal sensitivities of the LR active agent at the lower levels of 50░C and 10░C were not forthcoming. Perhaps most important to the interpretations was the fact that the responses were not normalized to those from the Viking LR instrument. The counting efficiency used on the clays was 75% compared to 3% for the LR. Hence all responses for the clays should have been reduced by a factor of 25, which would have placed them in the control or noise levels. In the last work cited above, the claims of replicating the LR data were reduced to state that “iron-enriched smectites . . . were shown . . . to simulate many of the findings of the Viking Labeled Release Experiments on Mars.” Considering that there is no direct evidence for clays on Mars, and the flawed nature of the experiments, the possibility that clays explain the LR Mars data seems vanishingly small.
9. Complexities of Independent Origin of Life: While listed last, this is really the penultimate reason responsible for discounting the LR Mars data as evidence for life. The origin of life is so poorly understood that the complexity posed by it alone would make the application of Ockham’s Razor favor a non-biological explanation of the LR data. However, the presumed evidence of microbial life in the two martian meteorites raises the possibility that an independent origin of life on Mars was not necessary for life to exist on that planet. If the biological fossils are confirmed, the principle of panspermia will be established. EETA79001 is only 600,000 years old, in effect, of the “modern” era on Mars. The environmental changes deemed by many as inhospitable to life already had occurred. Were microorganisms alive so recently, their survival to the present would be readily inferred.
The presence of microorganism fossils in the martian meteorites would also make a case against the oases theory88 which proposes that microorganisms may currently exist only in pools of liquid water postulated deep beneath the surface. Analysis89 of the physics of ejection of planetary material by meteoric impact concludes that materials escaping planetary gravity originate from, or near, the surface of the impact area. Thus, any fossils with the meteorites that fell on Earth could not be from deep oases. Furthermore, were there deep sites of living microorganisms, it is likely that volcanic action, frost heaving, or other mechanisms would eject such material to the surface. There any microorganisms could be widely distributed by the winds. The microorganisms might adapt to or become lyophilized by the surface conditions. Either way, they might still respond in the manner detected in the LR instrument upon being moistened with liquid nutrient under benign conditions. Regardless, the meteorites provide a now plausible vehicle for ejection into space, lyophilization by the space environment, survival of re-entry, and thus, interplanetary transportation of living microorganisms. The independent origin of life on Mars is no longer a barrier to acceptance of the LR data as evidence for life.
3. CONCLUSION
Many hypotheses have been advanced and tested in attempts to account for the well-characterized activity detected in the surface material of Mars by the LR experiment. As shown above, these hypotheses have themselves been found wanting. The demonstrated success of the LR and the exquisite sensitivity with which it has detected microorganisms during its extensive test program with its record of no false positives can no longer be denied. No non-biological approach published, or known to the author, has duplicated the LR Mars data. Some laboratory experiments have produced positive responses, but the detailed thermal sensitivity exhibited by the variety of controls conducted on Mars has remained elusive in all such tests compatible with martian conditions. On the other hand, a combination of known properties of microorganisms, perhaps even those possessed by single species, could reproduce all aspects of the LR data. The biological interpretation of the Mars LR results is left standing alone. Recent discoveries of life forms thriving in extraordinarily severe environments on Earth strongly indicate that any alien organisms arriving on Mars might well and widely adapt to their new home. Application of the scientific principle leads to a conclusion: the Viking LR experiment detected living microorganisms in the soil of Mars.
4. RECOMMENDATIONS
1. Add Life Detection Tests to Planned Missions. The above conclusion will require independent experimental confirmation before achieving general acceptance. No life detection experiments are planned for the NASA’s 10 Mars landers scheduled over the next decade. However, it is still possible to add life detection capability to them within the new NASA paradigm of “cheaper, smaller, faster.” Even without a dedicated life detection experiment, it is possible that confirmation of extant life may be achieved.