Today’s meteor explosion over Chelyabinsk is a reminder that the Earth orbits the Sun in a shooting gallery of asteroids, and that these asteroids sometimes hit the Earth. Later today, a separate and larger asteroid, 2012 DA14, will narrowly miss the Earth passing beneath the orbits of our communications satellites. We have the technology to deflect asteroids, but we cannot do anything about the objects we don’t know exist.

Discovered just one year ago by an amateur citizen observer, 2012 DA14 will fly only 17 thousand miles above Earth — the distance the Earth travels in just 15 minutes, and not much longer than many people travel on common air flights. So this truly is a close shave. In fact, 2012 DA14 will pass underneath our communications satellites as it flies by Earth.

This particular object is not large for an asteroid; it is about 160 feet across or roughly the size of an office building. It is not going to hit us on February 15, but it should serve as a wake-up call for planetary defense. Consider that just 105 years ago, an asteroid slightly smaller than this struck Earth in Siberia near Tunguska and completely flattened a forested area of 1000 square miles, an expanse larger than New York City or Washington D.C.

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