Wired Science: Any number of undiscovered near-Earth objects could one day careen into the Earth, and there is a lot of talk at the American Geophysical Union meeting about tracking them. So far, though, only one discovered object has seemed even mildly likely to hit our planet.
That asteroid is Apophis, a 900- foot [275m] asteroid. Calculations released on Christmas Eve 2004 appeared to show that there was a greater than 2 percent chance the asteroid would hit the Earth in 2029. The asteroid appeared ready to give the Earth its closest shave since astronomers began looking for such things. It was judged a 4 on the Torino Impact Hazard Scale for a short time, the highest rating any near-Earth object has received.
As it turned out, more precise observations brought the risk of collision down to just 1 in 250,000, but the scare sparked greater interest and study in the fields of asteroid detection and defense.
Even though the asteroid doesn't look like it's going to h
it Earth, on April 13, 2029, it will come closer to Earth than any other near-Earth object that we know of. It will pass just 18,300 miles [30,000km] above the planet's surface.
