Back in late 2004, there was a bit of excitement over asteroid 2004 MN4, which was given the highest rating on the danger scale for hitting Earth. The reason for the high rating is that it's a pretty good sized chunk of rock (400m) and not a lot of observations had been made to predict its orbit precisely. Fortunately, an impact was ruled out, just in time for the new year.
But it seems that old rumors die hard. Dispite having been poo-poo'd almost 2 years ago, sites are still reporting the danger but for a 2039 collision. Apparently they didn't read the article saying 2004 MN4 "poses no other impact probabilities with the Earth through the rest of the 21st century."
The 2004 MN4 scare isn't the only rumor that's persisted. Back in 2003, Mars made its closest approach to Earth in recorded history, giving astronomers, both professional and amateur and unprecedented view.
At that time, an Email began circulating stating that Mars would look "as big as the moon". Common sense should tell you that this is ridiculous. But amazingly enough, people started calling planetariums to find out about this event, disappointed to find out the truth.
But come summer 2004. The Email started circulating again. Snopes.com debunks it.
Summer 2005 and the Email is back!
And it seems that now, in 2006, the three year old Email is apparently still making the rounds. This time Universe Today has tackled the myth.
It seems that some people just don't get the memo. I expect that, until 2039, there will still be people saying that 2004 MN4 is still going to destroy all life on the planet, and that Mars is going to look like the moon.