It's hard to miss an asteroid the size of a truck exploding with all the force of a nuclear bomb. Such a space rock boiled across the sky near Chelyabinsk in southern Russia on February 15.

Space objects are a constant threat to Earth. In the worst case, the dust cloud from a major impact could shut down photosynthesis. No matter how much carbon dioxide humanity spews into the atmosphere, we may be powerless to prevent a kind of nuclear winter from the impact of an even bigger object, like 2012 DA14 which just passed within 17,200 miles of Earth.

That's closer than some of our Earth-observing satellites.

Big impacts have been trouble for life on Earth since the beginning, perhaps holding back life's first outbreak and pressing the reset button again and again throughout the planet's history. Just as it makes sense to take out an insurance policy against climate change, it makes sense to take out an insurance policy against spaceborne threats by spending a little bit more on the kinds of satellites and telescopes that can spot them.

Of course, the U.S. has been spending less on such observations in recent years. Our inability to adequately see ahead may yet prove our undoing, whether at our own hands or via the kind of massive meteorite that killed the dinosaurs.

—David Biello

[The above text is a transcript of this podcast.]