June 28, 2013
Russian Meteor Produced A Shockwave That Traveled The Globe Twice
Lawrence LeBlond for redOrbit.com - Your Universe Online
The Chelyabinsk meteor that blazed a trail across the morning sky in Russia this past February left a shocking impact on not just the Ural Mountains region, but the entire world.A new report published in the journal Geophysical Research Letters states the shockwave from the meteoric explosion on the morning of February 15, 2013 traveled around the globe -- not once, but twice.
Scientists, led by Alexis Le Pichon of the French Atomic Energy Commission, found that tremors produced by the explosion of the 10,000-ton object were recorded at 20 infrasonic monitoring stations around the world. The scientists said this is the first time these stations, which were designed to detect nuclear weapons testing, had detected "multiple arrivals involving waves that travelled twice round the globe [sic]."
The data was pulled from the International Monitoring System (IMS) network, which is operated by the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). While the IMS stations are designed to detect the ultra-low frequency acoustic waves from nuclear explosions, they are also capable of picking up explosions from other sources -- in this case, the blast from the Chelyabinsk meteor.
Pichon and colleagues wrote that the explosive energy of the meteor was the equivalent of 507,000 tons of TNT. In contrast, the force of the Hiroshima bomb dropped during WWII was only about 17,500 tons. February's meteor explosion rivaled that of the 1908 Tunguska meteor that exploded over Siberia, decimating tens of millions of trees over nearly 1,200 square miles.
The Tunguska meteor event is the subject of another investigation published in the journal Planetary and Space Science.
Researchers believe the 1908 meteoric event was caused by an iron-rich meteorite. The air blast has been estimated to have been the equivalent of 3 to 5.5 megatons (millions of tons) of TNT, hundreds of times more powerful than the Hiroshima explosion and still nearly ten times as powerful as the 2013 Russian meteor event.
Researchers, led by Victor Kvasnystya of Ukraine's National Academy of Sciences, studied microscopic samples of mineral debris from the Siberia impact zone that were trapped in peat and collected during the 1970s and 80s.
High-resolution imaging and spectroscopy revealed the presence of carbon minerals such as diamond, lonsdaleite and graphite. Lonsdaleite is typically found in carbon-rich material subjected to a shockwave, and is typically formed during meteorite impacts, said the researchers.
The lonsdaleite fragments also contained smaller inclusions of iron sulphides and iron-nickel alloys, as well as troilite and taenite, all commonly found in meteorite samples.
The minerals and ores found in the samples led the team to associate the Tunguska event with a meteorite source, especially since the composition is nearly identical to minerals found in the Canyon Diablo meteor that created Meteor Crater in Arizona.
The findings would make it implausible that the Tunguska event was associated with the Comet Encke, which is responsible for the Beta Taurids meteor shower. The Beta Taurids rain down on the Earth's atmosphere in late June and July, about the same time when the Tunguska event occurred.
As for the Chelyabinsk meteor, the National Science Foundation (NSF) reported in March that a network of seismographic stations recorded the blast wave as it crossed the United States. Those stations, which are used to detect earthquakes, were sensitive enough to also pick up and record the shockwave left by the meteor blast.
"The NSF-supported Global Seismic Network and EarthScope Transportable Array made spectacular recordings of the Chelyabinsk meteor's impact," said Greg Anderson, program director in NSF's Division of Earth Sciences.
"These recordings of seismic waves through the Earth, and sound waves through the atmosphere, are good examples of how these facilities can help global organizations better monitor earthquakes, clandestine nuclear tests and other threats," he added.