Space: Is the Earth Safe From Lunar Contamination?

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Fortunately, the possibility that living organisms exist on the moon is remote. But if they do exist, and in turn infect the astronauts, the Apollo 11 flight may indeed be an historic event.

With that ironic understatement, a doctor at the Manned Spacecraft Center in Houston last week summarized an increasing concern among some scientists that returning astronauts may contaminate the earth with strange and perhaps dangerous bugs. His statement added fuel to a controversy that broke into the open last month when it was revealed that NASA had relaxed its elaborate quarantine plans for the Apollo 11 crew (TIME, May 16).

Most scientists agree that there is little chance of any life existing on the moon. But they differ widely on the possible consequences to earth if there are lunar organisriis and any of them hitch a ride with the returning astronauts. University of Chicago Chemist Edward Anders and several of his colleagues are so unconcerned about the danger of contamination that they have volunteered to expose themselves "in every medically reasonable way" to any rocks that the Apollo 11 mission manages to bring back from the moon. They would be willing, they say, to swallow small samples to prove their point.

Escaped Fragments. The apparent boldness displayed by Anders and others stems from their strong doubts that lunar life exists and their conviction that quantities of lunar debris have been falling on the earth's surface for billions of years. Thus, they reason, even if there are lunar organisms, terrestrial life has long been exposed to them without any catastrophic results. According to their theory, meteors often strike the moon with enough momentum to knock lunar fragments loose at escape velocities. Most such fragments captured by the earth's gravitational pull would be incinerated as they plunge through the atmosphere. But those in a certain size range, the scientists say, would drift down and arrive on earth relatively unscathed, safely delivering any organisms they might contain.

Others are more concerned. Although he agrees that organisms might survive a moon fragment's entry into the earth's atmosphere, Cornell Exobiologist Carl Sagan is less confident that they could live through the heat generated by a meteor impact on the moon. For that reason he has doubts that lunar organisms have ever reached the earth and that terrestrial life has already proved its immunity. Sagan, like most other scientists, believes that the odds are high against life existing on the moon. But he cautions that there is "an exceedingly small risk of possibly great harm" in not maintaining strict quarantine procedures for the returning Apollo 11 astronauts. "Maybe it's sure to 99% that Apollo 11 will not bring back lunar organisms," he says, "but even that one percent of uncertainty is too large to be complacent about."

Inadequate Quarantine. University of Rochester Biochemist Wolf Vishniac is not particularly concerned about the Apollo 11 mission, which will bring back only surface samples. But Vishniac is convinced that more elaborate quarantine precautions should be taken thereafter. On later missions, he points out, astronauts will dig for samples from below the surface, where radiation and temperature variations are less severe and the prospects of life more likely.

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