Picture this: A 10-meter wide asteroid hits Earth and explodes in the atmosphere with the energy of a small atomic bomb. Frightened by thunderous sounds and shaking walls, people rush out of their homes, thinking that an earthquake is in progress. All they see is a twisting trail of debris in the mid-day sky:
This really happened on Oct. 8th around 11 am local time in the coastal town of Bone, Indonesia. The Earth-shaking blast received remarkably little coverage in Western press, but meteor scientists have given it their full attention. "The explosion triggered infrasound sensors of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) more than 10,000 km away," report researchers Elizabeth Silber and Peter Brown of the Univ. of Western Ontario in an Oct. 19th press release. Their analysis of the infrasound data revealed an explosion at coordinates 4.5S, 120E (close to Bone) with a yield of about 50 kton of TNT. That's two to three times more powerful than World War II-era atomic bombs.
The asteroid that caused the blast was not known before it hit and took astronomers completely by surprise. According to statistical studies of the near-Earth asteroid population, such objects are expected to collide with Earth on average every 2 to 12 years. "Follow-on observations from other instruments or ground recovery efforts would be very valuable in further refining this unique event," say Silber and Brown.