Perhaps most significant in the long, tortuous history seeking to determine what the Viking LR detected on Mars is that no condition or property inimical to the existence of life, or, indeed, even inimical to the survival and growth of some forms of terrestrial microorganisms, has been reported to exist on Mars.
Over the thirty years since the landing of Viking, more than forty attempts have been made to explain the LR results abiologically. To this date, no experiment has duplicated or realistically approximated the Mars LR positive and control results except when using living microorganisms.
Science is not a democratic process, and paradigm-breaking discoveries have always been subject to skepticism and years of delay before acceptance by the scientific community. With the failure of all proposed alternative explanations of the Viking LR results, the time for accepting life on Mars may be on hand. The credibility of the LR results has been significantly advanced by what has been learned about life since Viking. Life is no longer constrained to the thin, fragile film on, above, and below the surface of the Earth, as we were taught before Viking. We now know there is a "Biologic Imperative" on Earth. It has pervaded our planet's surface, depth and atmosphere, everywhere, including environments as hostile as some on Mars; with, perhaps, the only exception being red hot magma. Even if life never originated on Mars, we now know it could have been safely deposited there from Earth and/or other sources. Since testing of the constraints on viable interplanetary transport between Earth and Mars, it has become more difficult to imagine a sterile Mars than a living one. In fact, it is becoming apparent that Earth and Mars may be part of the same biosphere.