Apollo Project Missions to the Moon

NASA's human-crewed Apollo Project missions to the Moon (1969-72) stimulated a great deal of debate about forward and back contamination. Early in the 1960s, scientists began to speculate in earnest: Is there life on the Moon? Some of the bitterest technical exchanges during the Apollo Project concerned this particular question. If there was life, no matter how primitive or microscopic, scientists wanted to examine it carefully and compare it with life-forms of terrestrial origin. This careful search for microscopic lunar life would, however, be very difficult and expensive because of the forward-contamination problem. For example, all equipment and materials landed on the Moon would need rigorous sterilization and decontamination procedures. There was also the glaring uncertainty about back contamination. If microscopic life did indeed exist on the Moon, scientists wondered whether such possible microscopic lunar life-forms would represent a serious hazard to the terrestrial biosphere. Because of the potential extraterrestrial-contamination problem, some members of the scientific community urged time-consuming and expensive quarantine procedures.

On the other side of this early 1960s contamination argument were those scientists (including the first generation of exobiologists) who emphasized the suspected extremely harsh lunar conditions: virtually no atmosphere; probably no water; extremes of temperature ranging from 248°F (120°C) at lunar noon to -238°F (-150°C) during the long, frigid lunar night; and unrelenting exposure to lethal doses of ultraviolet, charged particle, and X-ray radiations from the Sun, as well as very energetic cosmic rays from throughout the universe. No life-form, they argued, could possibly exist under such extremely hostile conditions.

This line of reasoning was countered by other scientists, who hypothesized that trapped water and moderate temperatures below the lunar surface might sustain very primitive life-forms. And so the great extraterrestrial-contamination debate raged back and forth until finally the Apollo 11 expedition departed on the first lunar-landing mission. As a compromise, the Apollo 11 mission flew to the Moon with careful precautions against back contamination but with only a very limited effort to protect the Moon from forward contamination by terrestrial organisms.

The Lunar Receiving Laboratory (LRL) at the Johnson Space Center in Houston provided quarantine facilities for two years after the first lunar landing. What scientists learned during its operation serves as a useful starting point for planning new Earth-based or space-based quarantine facilities. In the future, advanced quarantine facilities will be needed to accept, handle, and test extraterrestrial materials from Mars and other solar-system bodies of interest in our search for alien life-forms (present or past).

During the Apollo Project, no evidence was discovered that native alien life was then present or had ever existed on the Moon. Scientists at the Lunar Receiving Laboratory performed a careful search for carbon, since terrestrial life is carbon based. Found in the lunar samples were 100 to 200 parts per million of carbon. Of this amount, only a few tens of parts per million are considered indigenous to the lunar material, while the bulk amount of carbon has been deposited by the solar wind. Exobiologists and lunar scientists have concluded that none of this carbon appears derived from biological activity. In fact, after the first few Apollo expeditions to the lunar surface, even back-contamination quarantine procedures of isolating the Apollo astronauts for a period of time were dropped after the Apollo 14 mission.

Has the life-on-the-Moon debate ended? Quite possibly it has not because of discoveries made within the last decade or so. The suspected presence of lunar water ice in permanently shadowed craters found in the polar regions of the Moon may revive some very modest portion of the "microscopic lunar life" debate of the early 1960s. Furthermore, here on Earth, scientists have discovered various extremophiles—very hardy microorganisms that are capable of living in extremely harsh environmental conditions. If these hardy life-forms have been discovered in the strangest places on Earth, what about elsewhere in the solar system in places where there is water?

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