A growing realization that it might be necessary to protect the planetary bodies from contamination led, in 1964, to the publication by COSPAR of a set of planetary quarantine requirements (PQR), which were subsequently adopted by the United States. They were ostensibly more scientific than the CETEX code of conduct in that they were based on an attempt to establish the probability of contamination by a given mission. Appropriate precautions, such as decontamination or sterilization, were taken as a result of the statistical analysis,20 a practice followed until 1982.18

Indeed, the possibility of contamination was considered from the very early days of the lunar exploration program. Research undertaken by the Rand Corporation had suggested that germs carried by a spacecraft from Earth could contaminate the lunar surface and invalidate any future searches for life. As a result, when America made its first attempt to send a spacecraft towards the Moon in August 1958, each section of the Pioneer spacecraft was sterilized with ultraviolet light before being assembled in a weather-tight room at the top of its launch gantry by technicians dressed in surgical gowns, gloves, and masks.

However, some questioned the need for sterilization. Dr. Harold Urey, one of the California Institute of Technology's most respected lunar scientists, thought that even if a square kilometer of the Moon were contaminated, some 30 million km ² would remain untouched for future research. Besides, he argued, the harsh thermal and radiation environment would kill any microbes attached to the...