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1 .This is Scientific American 60-Second Earth. I'm David Biello. Your minute begins now.
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2 .It's hard to miss an asteroid the size of a truck exploding with all the force of a nuclear bomb.
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3 .Such a space rock boiled across the sky near Chelyabinsk in southern Russia on February 15.
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4 .Space objects are a constant threat to Earth.
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5 .In the worst case, the dust cloud from a major impact could shut down photosynthesis.
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6 .No matter how much carbon dioxide humanity spews into the atmosphere,
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7 .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.
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8 .That's closer than some of our Earth-observing satellites.
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9 .Big impacts have been trouble for life on Earth since the beginning,
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10 .perhaps holding back life's first outbreak and pressing the reset button again and again throughout the planet's history.
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11 .Just as it makes sense to take out an insurance policy against climate change,
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12 .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.
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13 .Of course, the U.S.has been spending less on such observations in recent years.
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14 .Our inability to adequately see ahead may yet prove our undoing,
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15 .whether at our own hands or via the kind of massive meteorite that killed the dinosaurs.
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16 .Your minute is up, for Scientific American 60-Second Earth. I'm David Biello.
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