In the novel and movie versions of "War of the Worlds," the aliens can't be stopped, except for one thing, and that's Earth pathogens. Our stupid invaders never considered the potential dangers, and therefore didn't take steps to make sure they were protected, evidently. And what about alien pathogens and how they'd impact Earthlings, which apparently weren't considered?
And as we continue to explore other worlds, we have to consider what we bring with us:
If we want to go to Mars, we have to watch out for Earth microbes
And as we continue to explore other worlds, we have to consider what we bring with us:
If we want to go to Mars, we have to watch out for Earth microbes