February 15, 2013
Meteor Strikes Like Russian Event Only Occur Once Every 10 To 30 Years
Lawrence LeBlond for redOrbit.com - Your Universe Online
As reports continue to stream in through various media outlets on injuries, damages, and the science behind such events, it seems this morning´s (February 15) meteor strike in Russia´s Ural Mountains region has left a pretty big impression far and wide.
At last count more than 1,200 people (at least 200 children) are believed to have been injured by the meteor, most from broken glass produced by the exploding object's shockwave. As people were starting their day, either heading to work or opening their schoolbooks, an explosion thundered across the region, with the city of Chelyabinsk taking the brunt of the impact.
While the 11-ton meteor exploded more than 18 miles above the Earth and never made a direct impact, debris from the break-up rained down over at least six cities with a large fragment landing in a nearby lake in Chelyabinsk.
Although the morning cosmic visitor left a path of destruction in its wake, thankfully no deaths have been reported as a result of the strike. The thunderous boom, however, sent car alarms going off, disrupted mobile phone networks and may have left some with a sense of fear that the end of the world was upon them.
That fear, if it was truly felt, may have stemmed from anticipation of another event that occurred earlier this afternoon, several hours after the meteor made its appearance. At about 2 p.m. EST this afternoon, asteroid 2012 DA14 made a record approach of Earth as it streaked by about 17,000 miles above the third rock from the sun.
While there was no chance of that asteroid impacting Earth, many may have tied this morning´s event to that one. Professor Alan Fitzsimmons of the Astrophysics Research Center at Queen´s University Belfast, assured citizens of the Earth that there was no connection between the two.
“One reason is that 2012 DA14 is approaching Earth from the south, and this object hit in the northern hemisphere,” he told BBC News. “This is literally a cosmic coincidence, although a spectacular one.”
While there is no chance that 2012 DA14 will impact Earth, one still has to wonder how often events such as this morning´s Russian meteor strike occur.
Professor Edwin Bergin of the University of Michigan´s Department of Astronomy, told redOrbit that a meteor the size of the one that struck this morning “would occur every 10 to 30 years or so “¦ but the really big ones (km-size) are thought to occur once or twice every million years.”
He continued to say that since the Earth is largely covered by ocean, it is likely that many events go unnoticed.
He said smaller and “more porous” objects, such as comets, “might break up high in the atmosphere while other denser rocks such as asteroids would reach deeper in our atmosphere. Whether an object will reach the ground will depend on its size, the trajectory of the impact, and its density.”
For those larger ones that do have the chance to make an impact, it would seem sensible to have people in place combing the night skies picking them out with the latest high-tech equipment.
Bergin said there are telescopes with “CCD arrays” that do hunt out large objects traveling through space, but for the most part these are more likely to be used for tracking much larger objects, such as asteroid 2012 DA14.
He told redOrbit that, typically, objects the size of the Russian meteor go undetected, as astronomers are busy looking for objects out there that “cause much more devastation.”
In particular, the asteroid that rocked Siberia in 1908, known as the Tunguska Event, may have been one that would have been caught by near-earth object-hunting telescopes.
While this morning´s meteor strike may have been reminiscent of the 1908 Tunguska Event, Bergin said it was nowhere near the equivalent of that one. “Estimates right now, and these may change, are hundreds of kilotons of TNT. Tunguska was estimated to be 10 megatons of TNT.”
Still, he noted, this morning´s occurrence “is the biggest explosion or event in recorded history since Tunguska!”