The Earth will narrowly avoid a big collision next week. NASA says that asteroid DA14 will come within 17,000 miles of us Feb. 15. That may sound like plenty of breathing room, but the asteroid will actually sweep closer than some weather satellites do.
So what would happen if that asteroid actually did hit us? Happily, we can calculate that! Jay Melosh, an atmospheric scientist at Purdue, has created a nifty little “impact calculator” that lets you figure out the consequences of a large asteroid hitting the Earth.
In this case, DA14 is about 45 meters wide, weighing roughly 130 million kilograms. If that asteroid plopped into a nearby ocean — say, 100 kilometers away — then nearby cities would be fine. According to the calculator, we'd barely notice the resulting waves, though the sound of the asteroid exploding in the air would be loud enough to hear for hundreds of miles around.
And what if DA14 hit land? The calculator notes that the asteroid would begin to break up in the air — by the time they hit land, the fragments likely wouldn't be big enough to form a deep crater in the Earth, although you certainly wouldn't want to be standing under one of the chunks:
Still, DA14 is a relatively small asteroid. Consider instead YU55, which wandered close to the Earth back in 2011 and was much bigger, 400 meters in diameter. That would have caused much more damage, according to the Purdue team: "Sixty miles away from the impact site the heat from the fireball would cause extensive first-degree burns. The seismic shaking would knock down chimneys and the blast wave would shatter glass windows.” If YU55 had landed in the ocean, it’d create tsunami waves 60 feet high.
The Purdue site also has a list of famous asteroid impacts from the Earth's past. The big Meteor Crater out in the Arizona desert was caused by an object that was roughly the same size as DA14, but made of a different material and considerably more dense. That asteroid would have been much more noticeable to any humans standing nearby.
In any case, DA14 isn't going to hit the Earth next week — and, in fact, it's not likely to collide with us for at least the next century as it meanders around the sun. But other surprises could still be in store. As my colleague Brian Vastag reports, NASA has identified about 95 percent of the large asteroids lying in our path but only about 1 percent of the smaller asteroids, like DA14, that could conceivably hit Earth.