The Viking Labeled Release Experiment and Life on Mars

This chemical will oxidize the LR compounds to produce CO2. However relatively strong concentrations (approximately 2%) of H2O2 are required to emulate the amplitude and kinetics of the LR Mars positive responses. The most significant fact countering the H2O2 theory is that H2O2 and any of its proposed derivatives do not approximate the thermal sensitivity of the martian agent causing the LR responses. At 50░C, 90% H2O2 decomposes at only 0.001% per hour39. Of numerous attempts to simulate those results with H2O2, none reported has succeeded under conditions consistent with those on Mars. H2O2, highly sensitive to destruction by solar UV, has an expected lifetime in the martian atmosphere of less than one day. Any deposition of H2O2 from the atmosphere to the soil is likely too small to account for the LR results40. Based on the UV lability of H2O2, it is difficult for it to account for the LR activity. In addition, experiments41,42 reporting the formation of organic matter from simulated sun-irradiated martian atmosphere demonstrated that the organic matter accumulated despite the continuous incidence of the UV light. Evidently, the H2O2 formed under these simulated martian conditions was not made in sufficient quantity or did not survive the UV to oxidize the organic matter as fast as it was synthesized. The lifetime of H2O2 would be further reduced by the catalytic effects of y-Fe2O3 reported43 as likely to be extensive on Mars.

The re-examination of the Mars PR data also has repercussions for the H2O2 theories. The theories propose that there is oxidant in the soil. Why did that oxidant not destroy the organics formed and detected within the PR?

A variant chemical model proposing UV formation of peroxonitrites44 in the soil has been proposed since the review cited above. Aside from its failure to explain the result in the sample taken under the rock, this theory has not demonstrated the thermal sensitivity of the agent detected by the LR. Also, the formation of peroxonitrites would require amounts of nitrogen in the Mars soil in excess of the limit set by the Viking elemental analysis45.

A general question about attributing the failure to find organics on Mars to peroxide is the finding46 of H2O2 in ancient permafrost cores on Earth, where the oxidant did not eliminate organic matter or life. Being nearer to the sun and having more water vapor than Mars does in its upper atmosphere, Earth experiences the formation of H2O2 in amounts greater than does Mars. Yet, H2O2 was not inimicable to the development of life and the accretion of organic matter on Earth. Life developed enzymes to protect against this oxidant, and many species came to utilize it in their energy-producing metabolic processes.

3. No Liquid Water; Extreme Environment: Next to the peroxide theories, the most vigorous defense of the chemical nature of the LR results stems from the beliefs that all life must have access to water in liquid form and that none is available on the surface of Mars. Moreover, it has been stated47 that the atmospheric pressure at the surface of Mars is below the triple point of water and likely has been so for several billion years. This is not supported by data obtained by the Infrared Interferometer Spectrometer (IRIS) experiment48 aboard the Mariner 9 Mars orbiter. It reported that “Extensive regions have been found where the surface pressure exceeds the triple-point pressure of water” and that “under temperature conditions which frequently occur on Mars, liquid water can exist in equilibrium with its vapor.” A recent publication49 of Viking data provides a graph, FIG. 2, showing that, over a full martian year, the surface atmospheric pressures at both Viking landing sites continuously exceeded the triple point pressure for water. Further, inspection of the Viking data shows50 that the temperature of the top several millimeters of soil beneath the Viking Lander 2 sampling head rose to 273░K (the temperature at which ice liquifies) where it remained for at least several minutes. This is evidence for the melting of ice into liquid water. The thermal absorption of the metallic sampling head may have been responsible, but its thermal adsorption is likely equaled, or exceeded, by that of martian rocks. Surface temperatures in the southern latitudes at the start of summer were seen to exceed 273░K for several hours per day. Thermal inertias for large areas of Mars range above 6, and above 30 for bare rocks. Albedos of unfrosted martian ground are as low as 0.095.51 Viking orbital data52 also support the presence of liquid water in the upper few millimeters of the martian surface.

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