Also, as a followup, what were the US' plans if they came into contact with extraterrestrial life?
If by "hostile extraterrestrial life" you mean little green men, they had no weapons, although I'd hate to get whacked in the head by one of those geologist's hammers.
However if you mean microorganisms then they did take precautions. After they returned to earth the astronauts were put into quarantine. The practice was dropped after Apollo 14.