Why NASA tracks asteroids

For a while, astronomers thought asteroid TX68 might pass close to Earth; reeeeeally close, like as close as a satellite. Thanks to additional data, they figured out that wasn't likely after all. But TX68 was a good excuse to look at asteroids that do pose a risk of hitting Earth and what we're doing it about it. Read more here. (Relax, the risk is even lower than your odds of winning the lottery).