Did I Mention an Asteroid May Kill You?
Planet killers are the biggest worry, obviously, followed by city killers. One way you can tell the science of asteroid risk is young is that it has not yet developed bureaucratic-sounding euphemisms. Planet killers are exactly what they sound like. Sixty-five million years ago, a planet-killer asteroid a little bigger than Mount Everest crashed into the Gulf of Mexico near Mexico’s Yucatán peninsula, creating the Chicxulub crater. Seventy percent of all living species (plants and animals) were wiped out, including the dinosaurs. The impact on human beings was zero because we had the good sense not to exist (and would not until 300,000 years ago). Within the past million years, according to James Garvin, chief scientist at NASA’s Goddard Space Flight Center, four half-mile objects slammed into Nicaragua, Bolivia, Ghana, and Kazakhstan. We don’t know the consequences, exactly, but Garvin said, “It would be in the range of serious crap happening.” Oscar Fuentes-Muñoz from the University of Colorado, Boulder, says we’re probably good for 1,000 years, based on NASA’s cataloging of the 1,000 planet killers that we know are out there. Scientists believe these represent 95 percent of all the planet killers in the general vicinity. Thursday’s planet-killer near-miss, for instance, has been anticipated since 2011.
City killers are more of a problem. There are people still living (not a lot) who were alive at the time of the last one on June 30, 1908, when an asteroid the size of a 13-story building exploded six miles above the Podkamennaya Tunguska River in a remote corner of Siberia. The force of the explosion knocked over or set fire to trees for miles around and killed scores of reindeer. Fortunately, only about 30 people (mostly reindeer-herders) lived near the blast, of whom a reported three were killed. Word of the collision traveled slowly; our information about the event is sketchy because two decades passed before scientists appeared on the scene. What’s certain is that, had this been a populated area—as many more places on earth are, 116 years later—the death toll would have been catastrophic.
Scientists have been able to locate only about 40 percent of the 30,000 or so city-killer asteroids they believe to reside in earth’s vicinity. The European Space Agency keeps a list of 1,624 city killers that pose a “non-zero” risk of colliding with the Earth over the next century. But keep in mind that city killers often take astrophysicists by surprise; the one passing near Earth June 29 was first spotted only last year.
