Asteroid Exploded in Earth's Atmosphere

A small asteroid exploded over Africa this week following what astronomers said was the first firm prediction of an incoming space rock.

It did not strike Earth.

The asteroid was about the size of kitchen table, astronomers estimated, and they think the explosion (caused by the pressures of slamming into the atmosphere) left nothing but perhaps a few small bits to fall to the surface.

No photographs of the explosion have been reported, owing to the remote location of the object's path over Sudan. But the explosion was recorded by an infrasound array in Kenya. Peter Brown at the University of Western Ontario estimated, based on the infrasound data, that the asteroid exploded at 0243 UT with an energy of somewhere between 1.1 and 2.1 kilotons of TNT.

On Monday, NASA researchers and other scientists announced that the space rock, named 8TA9D69, would enter the air at 10:46 p.m. ET (0246 UT) on Oct. 7 over northern Sudan. Such events occur a few times every year, but never before had one been predicted. The object was expected to create a very bright fireball that, for anyone who might have seen it, would have been far more dramatic than the typical shooting star resulting when small debris streaks through Earth's atmosphere.

"A typical meteor comes from an object the size of a grain of sand," Gareth Williams of the Minor Planet Center explained just before the highly anticipated event. "This meteor will be a real humdinger in comparison!"

There has been one visual confirmation of the exploding fireball, according to Jacob Kuiper, a general aviation meteorologist at the National Weather Service in The Netherlands, told pilots to keep an eye out.

"I have received confirmation that a KLM airliner, roughly 750 nautical miles southwest of the predicted atmospheric impact position, has observed a short flash just before the expected impact time 0246 UTC," Kuiper said. "Because of the distance it was not a very large phenomenon, but still a confirmation that some bright meteor has been seen in the predicted direction."

The rock was discovered by an ongoing survey at Mt. Lemmon run by the University of Arizona as part of the NASA-funded Catalina Sky Survey for near-Earth objects.


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