[Blue Fire]

On even further reflection, I'm thinking that a comet display visible even in daylight would get the most positive attention to astronomy. More folks would be likely to look up more often (and possibly ponder longer) and have a greater appreciation of "the heavens" in general. But the comet wouldn't necessarily carry any notions of threat with it except to those people that didn't understand what they were seeing. Of course I think there would be an awful lot of people that would panic at first, not understanding what they were seeing with a sort of "War Of The Worlds" mentality. So maybe that effect itself would bring greater awarness of both the beauty of astronomy and the possible threats to Earth by extraterrestrial objects and other astronomical phenomena like Coronal Mass Ejections and lethal radiation.

The asteroid passing harmlessly between Earth and Moon, at this point seems to have the least potential impact on humanity especially if not observed by the majority of the public. But then, on the other hand, once the media got it's hands on this event, a Very near miss might just have a huge positive impact on humanity in terms of programs out there to identify and deal with threats like this. It might just have the Best positive impact in terms of the future preparedness of the human race to deal with and survive these kinds of threats.