It's always an event when a large asteroid comes anywhere near Earth. We've all seen enough disaster movies to know what would happen when asteroids and the Earth collide.
That's why NASA tries to keep track of any large objects headed in Earth's direction, even though it's a tough job given how large space is and how relatively small asteroids are (find out how you can help). That's why even when NASA picks up an object, it can sometimes get the details wrong.
That's what happened with the approaching asteroid 2013 TX68. It's throwing off a lot of glare from the sun, and is only the size of a blue whale, so it's a bit hard to see exactly what it's doing.
Originally, NASA predicted it would shoot past Earth on Saturday, March 5. As it's gotten closer, however, NASA has revised its estimate to Tuesday, March 8.
As for how close the asteroid is going to get, NASA still isn't sure. It could be as close as 15,000 miles, which is much closer than the 22,300 miles where our GPS and other satellites hang out, or it could be 40 times farther away than the moon. NASA says there's no chance of it hitting Earth - this time.
However, when it comes by again next year, it has a chance of hitting Earth. If it did, it would explode in the atmosphere and the energy it released would be on the order of a nuclear explosion. Fortunately, the odds are only 1 in 250 million, so no one is really that concerned.
As the asteroid goes past, NASA should be able to lock down its orbit with much more accuracy for better future predictions.
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