The Viking Labeled Release Experiment and Life on Mars

Of particular interest are the results obtained when lichen were tested by the LR. The lichen responded very vigorously upon initial contact with the aqueous nutrient, but the rate of evolution quickly decreased and essentially ceased after only 24 hours. A comparison of the lichen incremental responses with those of the Mars LR is presented in FIG. 8. This suggests the possibility that too much water could have been a factor in both experiments. The above cited publication argues that increased gas evolution upon the second injection would have supported the biological nature of the response. However, had a second evolution of gas occurred, might not the argument have been made that water had become the limiting factor following the first injection, and that its resupply allowed a chemical reaction to continue?

6. No Visual Evidence: It was reported78 that a study made by the Viking Lander cameras showed no evidence for macro or micro forms of life. However, a detailed analysis of all the Viking Lander images79 revealed colored spots on many of the rocks and colored areas of the surface ranging from ochre to yellow to olive and green. A digital spectral analysis of the spots on the rocks as seen in six imaging channels (RBG and three near-IR) comported closely to that of images of lichen-bearing rocks. These rocks were viewed by the Viking cameras in the simulated Viking 1 Lander site and processed through the Viking Imaging System. The greenest objects in both fields of view were spots on the martian and Earth rocks. The respective digital numbers for hue, saturation and color for the spots in both images were similar. Subsequently, the greenish colors were independently confirmed80,81 with the additional observation that the green spots on the rocks were elevated by 0.1 to 1 mm above the background surface of the rock. While unusual weathering might account for the elevation of the spots and the changes observed, it has been suggested82 that lichen, or similar colonial microorganisms, could more readily satisfy the observations. Called “the pioneers of vegetation”, lichen are the first life forms to appear on bare rock. Lichen have also been reported83 to subsist when the only source of water is atmospheric vapor. The atmosphere at both Viking Lander sites was at or near water vapor saturation diurnally, and frost was seen in many of the morning images.

FIG. 9 is an image of three near-field rocks at Viking site 1 which were selected for study. The image was calibrated by the Viking Imaging System to provide the truest Mars colors. FIG. 10 is a heretofore unpublished set of 3 images encompassing most of the same area and taken at intervals of one martian year (two Earth years). All three images are treated identically, and closely approximate the calibration of FIG 9. The pictures are taken within several degrees of the same sunangle in order to permit comparison without mistaking light or shadow effects for true differences between successive images. The field of view was limited because of power conservation during the later portion of the extended mission. It is apparent that changes have occurred over time. Some of the near-field differences between the first two images were caused by sampling of the soil that occurred after the first image was taken. However, changes in both the near and distant fields cannot be associated with the sampling activity. A comparison of the same near-field fine surface structures among the three images shows that aeolian effects were essentially nil (the only apparent changes being from slumping that occurred around the dug hole). In particular, attention is directed at the foreground rock, which exhibits a major change in its patterned colored areas, and to the distant background where extensive pattern and color changes are evident. In several ways, then, the Viking Lander images provide evidence consistent with a biological interpretation of the LR data.

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