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Organic Matter and the Moon, by Carl Sagan (1961)

Chapter: VIII. SUMMARY

« Previous: VII. BIOLOGICAL CONTAMINATION OF THE MOON
Suggested Citation:"VIII. SUMMARY." National Research Council. 1961. Organic Matter and the Moon, by Carl Sagan. Washington, DC: The National Academies Press. doi: 10.17226/18476.
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Page 40
Suggested Citation:"VIII. SUMMARY." National Research Council. 1961. Organic Matter and the Moon, by Carl Sagan. Washington, DC: The National Academies Press. doi: 10.17226/18476.
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Page 41

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VHI. SUMMARY The rate of synthesis of organic molecules by solar ultra- violet radiation in the primitive lunar atmosphere is estimated. The consequent lunar surface density of organic molecules is very high, probably between 1 and 10 gm cm"2. As the lunar atmosphere was dissipated, heat and radiation produced organic molecules of great complexity from the deposited material. Such organic matter would now be situated beneath overlying layers of meteoritic and other surface debris, at a depth of possibly a few tens of meters, although some distribution throughout the dust may be expected. Reports of gas clouds on the lunar surface are discussed and shown to be probably unreliable. However, the observations of Kozyrev, if verified, would be evidence for lunar subsurface or- ganic matter. Kremlin's theory of heat localization by hydrostatic pressure in dust indicates that constant, biologically-optimum temperatures exist at just the level that surviving primitive organic matter is probably localized. Therefore the possibilities of multiplication of terrestrial microorganisms on the Moon and of survival of in- digenous lunar organisms from the early history of the Moon are not as remote as has sometimes been thought. The probability for survival of a terrestrial microorganism, accidentally deposited on the Moon by an impacting lunar probe, is computed. A population of the least radiosensitive dormant anaerobic microorganisms would be totally destroyed in hours if exposed to solar ultraviolet radiation. The resulting organic dissociation products would remain intact for much longer periods of time; 0. 1 to 10 years if the lunar surface magnetic field strength is much less than 10"2 gauss (so that incident solar protons are magnetically deflected), and 104 to 105 years if the field strength exceeds 10"2 gauss. Organisms shielded from solar illumination, perhaps in congealed dust matrix interstices, would survive cosmic radiation and natural radioactivity for 109 years or more. Lunar subsurface temperatures are not too high to impede survival. The possible kinds of lunar biological contamination are then discussed. Because of the small absolute amount of terrestrial organisms and organic matter likely to be deposited by probe, and their separation in depth from indigenous lunar organisms and 40

organic matter, it is improbable that the two will be confused. But the explosive reproduction of only a very small number of terrestrial microorganisms in indigenous organic matter, and the disruption of the ecologies of hypothetical lunar organisms, are remote but non-negligible possibilities. It is recommended that all lunar probes be thoroughly de- contaminated, and that the first soft-landing probes be equipped for chemical analysis and biological plating of subsurface samples. 41

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The immediate future seems to hold both the promise and the responsibility of extensive contact between man-made objects and the Moon.

Current United States plans tentatively call for the soft landing on the Moon of instrumentation designed to detect indigenous organisms or organic matter, possibly in a roving vehicle, by 1964-67 in the Surveyor and Prospector Programs. The Soviet Union apparently has the capability of performing similar experiments at an earlier date. It is clear that positive results would give significant information on such problems as the early history of the Solar System, the chemical composition of matter in the remote past, the origin of life on Earth, and the distribution of life beyond the Earth. By the same token, biological contamination of the Moon would represent an unparalleled scientific disaster, eliminating possible approaches to these problems. Because of the Moon's unique situation as a large unweathered body at an intermediate distance from the Sun, scientific opportunities lost on the Moon may not be recoupable elsewhere.

This monograph is concerned with the possibility of finding indigenous lunar organisms or organic matter, and with the possibility of their contamination by deposited terrestrial organisms or organic matter.

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