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. Pathfinder is now enroute to Mars for a July 4, 1997 landing.
Its lander is equipped with a camera having better color and spatial
resolutions than did Viking's. It is possible that a close-up picture of a
rock might show clear evidence of biological colonies. A search for such
evidence should be a Pathfinder priority.
2. Use Hubble Telescope. The Hubble Telescope
should be used to seek evidence of large areal changes in the color and
patterns of the martian surface and seek to correlate them with
atmospheric water vapor and climatic seasons. Useful images that already
may exist in the Hubble files should be compared.
3. Seek Chirality in Mars Samples. Perhaps the
surest robotic means for unequivocal distinction of biological from
chemical reactions is a test for chiral activity. For some yet unknown
reason, or by chance, when the first living cells came into existence
their enzymes were chiral specific. They catalyzed protein-building
reactions with L-amino acids only. They had a similar preference for
L-carbohydrates over D-forms. Throughout the evolution of all living
forms, these preferences have been genetically transmitted. This
peculiarity of living systems provides a ready means of distinguishing
them from chemical reactions. Chemical reactions, without the intervention
of man, cannot distinguish between L- and D-isomers. On the other hand,
all known life forms utilize and make virtually only the L-form of amino
acids.
