A theme in movies about space travel, and in particular about visitors from outer space, is the dangerous microbe that arrives, against which there is no human immunity. For those who wish the populace to keep aliens at arms length, this seems a perfect scare tactic. To test the response, both to the physical reaction to various substances that were candidates for such scare tactics and of the psychological reaction to such substances arriving from the sky, several small and isolated towns were selected at random as guinea pigs. As it was to be clear that the infecting substance came from outer space, it was dropped in a rather dramatic fashion from above, the result of a sky shot that burst and splattered when it reached a certain altitude. CIA plants in the town, postured as transients or lurking in bushes with listening devices, watched and recorded the resulting reactions.
To the dismay of the cooks, the brew did not result in the panic and fear of the unknown that was expected. To the contrary, the townsfolk in all the towns so subjected to this experiment refused to do anything but scrutinize the gelatin substance that was dropped on them from the sky. They hired scientists, and elicited free examinations, and probed and questioned. As with most scams, they only succeed when such scrutiny is prevented, as inevitably there is evidence that points to the truth. In order to infect humans, germs of some sort that grow in human tissue had to be involved, and thus human tissue to support these germs until they could reach a new host were required. Thus, the alien glop proved to have human cells present, a dead giveaway to the origin of the infecting gelatin. And since the reaction of the public was so alarming, these particular experiments are not likely to be repeated.