Russian meteor blast 'heard' around the world
The shock wave from Friday's (Feb. 15) meteor explosion
above Russia sent subsonic waves through the atmosphere halfway around the
world.
Up to 11 sensors in Greenland, Africa, Russia's Kamchatka
Peninsula and other far-flung regions detected the Russian meteor blast's
infrasound, or low-frequency sound waves. The sensors are part of the global
network of 60 infrasound stations maintained by the Comprehensive Nuclear Test
Ban Treaty Organization (CTBTO).
Infrasound's long wavelengths (about 20 to 0.01 Hertz)
can travel far distances in the atmosphere, at frequencies humans can't hear.
Elephants, whales and even pigeons use infrasound for communication and
navigation, scientists have discovered.
The CTBTO relies on Infrasound arrays to help determine
the location and size of atmospheric explosions. Man-made explosions, such as
bombs, produce a different infrasound pattern than natural fireballs like
shattering meteors.
Based on scrutiny of infrasound records, NASA scientists
concluded the fireball released about 300 kilotons of energy, said Bill Cooke,
lead for the Meteoroid Environments Office at NASA’s Marshall Space Flight
Center in Huntsville, Ala.
That's about 20 to 25 times more powerful than the atomic
bombs dropped in World War II, but still smaller than Siberia's Tunguska meteor
explosion in 1908, which released 10 to 15 megatons of energy (equivalent to
the Castle Bravo device, the most powerful atomic bomb tested by the United
States).
"This was a moderate explosion," said Paul
Chodas, research scientist in the Near Earth Object Program Office at the Jet
Propulsion Laboratory in Pasadena, Calif.
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