Oct 12, 2008 04:00 PM
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With all the hullabaloo about giant asteroids that could destroy us, we tend to forget the little guy. Luckily, NASA's Catalina Sky Survey has it covered. Last Monday, CSS astronomers caught sight of an incoming object zooming toward the Earth, and by the time of the asteroid's impact on Tuesday, NASA engineers had mapped out its trajectory almost exactly. This is "the first time we were able to discover and predict an impact before the event," announced Donald Yeomans, the manager of NASA/JPL's Near-Earth Object program — and I'm guessing he did it with no small amount of glee.
No one yet has a photo of the fireball that occurred as the asteroid (dubbed 2008 TC3) broke up in the atmosphere, and meteorite fragments will be difficult to find — the impact spot is in northern Sudan near Darfur. But Russian stargazers S. Korotkiy and T. Kryachko, of the Kazan State University Astrotel Observatory, released an animated picture of 2008 TC3's path toward Earth:
Nature reports that NASA was able to give out early warnings of the impact:
On Monday, once Yeomans' office had confirmed the incoming asteroid, he called NASA headquarters in Washington DC, which publicized the impact about seven hours before it occurred. If, however, the incoming object had been 50 to 100 times bigger than it was, the warnings would have been very different. "We would have found out several days sooner," Yeomans says, and arrangements would have been made to get people out of the area of impact.
Alerted of 2008 TC3's proximity and the possibility of seeing a fireball, a Dutch pilot with KLM reported seeing a quick flash in the sky from 1400 kilometers away. An astronomer from Western Ontario even managed to estimate the size of 2008 TC3:
... astronomer Peter Brown of the University of Western Ontario in London, Canada, was able to confirm that the space rock hit the atmosphere at around 02:45 GMT on Tuesday, within minutes of the predicted time and at the predicted location. Brown used data from a Kenya-based array of seven microbarometers, which record atmospheric sound waves to monitor countries' compliance with the Comprehensive Nuclear Test Ban Treaty. The infrasound signals show that the asteroid hit the atmosphere with an energy equivalent to detonating one to two kilotonnes of TNT.
"We can infer from that energy that 2008 TC3 was about three metres in diameter," Brown says.
Though 2008 TC3 was never listed as a potentially hazardous asteroid, its pre-impact discovery and analysis is still an encouraging development for NASA/JPL. Before 2008 TC3 ever entered Earth's atmosphere, astronomers were tracking its progress, and as far as they can tell it burned up just where they said it would. If we can predict the impact of objects this small, it bodes well for our ability to mitigate the imagined disaster scenarios of major impacts.
Great balls of fire [Nature News]
News and information about asteroid impact [Spaceweather.com]
Image from NASA/JPL.
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