THE PRESENT-DAY SPACE PROGRAM can be considered an outgrowth of the development of military rocketry during World War II and the decade that followed. It is true that nonmilitary rocket research had taken place earlier. Space exploration would probably have come about eventually, even without this development, but the ready availability of the necessary hardware and engineering technology greatly accelerated the first ventures into space. The logic behind a space program, however, was much more than a desire for a spectacular engineering feat or a matter of political rivalry between major powers, although these may have been significant factors. Earth-bound astronomy had its limitations, and many important scientific questions could be answered only by actual exploration of space. Not the least of these questions concerned biology. Was life restricted only to the planet Earth?
Man had always thought not. The ancients had populated the sky, as had later science fiction writers, exemplified by H.G. Wells in his War of the Worlds. Modern-day biologists speculated on other worlds being populated too, but they thought mainly in terms of microorganisms or simple life forms which would be the first to evolve and would be present whether higher forms evolved or not. They were concerned lest in the rush to enter space their science would suffer. After all, had not the War of the Worlds been won by the bacteria of Earth? Could this conflict not be duplicated, say on Mars, by carelessness in early space ventures before man ever had a chance to look for extraterrestrial life there? Man could do little that would change the geology of the planets, but their biology, if any existed, could be radically changed even within a decade or so. Planetary quarantine arose from these considerations.