Space rock fires a warning shot
Courtesy of Science/AAAS
When a known asteroid passed within 28,000 kilometers of Earth on February 15, astronomers hoped it would serve as a wake-up call about the danger of meteorite impacts. As it turned out, astronomers got more than they had bargained for. On that same day, a 19-meter-wide space rock plowed through the atmosphere and exploded over southwestern Russia near Chelyabinsk, shattering windows and causing more than 1,600 injuries. The largest recorded meteor since 1908 spurred scientists and government officials to reevaluate impact risks and increase monitoring and preparation for future events.
In November, researchers led by planetary scientist Peter Brown of Canada’s University of Western Ontario analyzed the last two decades of impact data and concluded that rocks the size of the one responsible for the Russian meteor probably strike Earth once every 30 years or so (SN: 11/30/13, p. 6). The previous estimate, based on ground-based telescope surveys that count up nearby space rocks of various sizes, was once every 120 years. Ground-based telescopes can spot giant, civilization-threatening asteroids in Earth’s orbital neighborhood but identify only a tiny fraction of rocks tens of meters wide.
Scientists hope a series of new ventures will increase their understanding of impact threats. In August, NASA announced that it would revive a decommissioned space probe, the Wide-field Infrared Survey Explorer, to conduct a three-year survey of near-Earth objects. Meanwhile, the private B612 Foundation plans to launch a telescope by 2017 that would spot nearby asteroids as small as 30 meters across. And in October the United Nations approved an International Asteroid Warning Network to keep a census of potentially dangerous rocks and a Space Missions Planning Advisory group to consider ways to deflect an incoming asteroid.
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