The Chelyabinsk meteor explosion that occurred last year in Russia validated what many scientists knew: that a meteorite of even modest size can wreak havoc on the planet.
Their theories, formulated through the observation of the evidence left behind at the Tunguska site, where a larger meteorite exploded more than a century ago devastating any arboreal life for 2,150 square miles, showed that if the meteorite at Tunguska had struck in a populated place instead of the far reaches of the Siberian steppes, the death toll would have been enormous. That meteorite is believed to have been between 200 to 620 feet in length. But the meteorite at Tunguska, just like the one at Chelyabinsk, did not effect such extensive damage because of an impact with the earth, but rather from the 30 megaton blast that occurred about 5 miles in the Russian sky, a force 1000 times greater than the Hiroshima bomb.
The Chelyabinsk event reminded scientists that meteorite strikes such as the recent one, and the larger one at Tunguska, are not relegated to the past, and that what we have learned from the latest event should warn us of other possible, and likely larger, events of the same nature.
While the 500 kiloton explosion over Chelyabinsk was modest compared to Tunguska, it is a glimpse of what could be coming down the proverbial pike. There is a pattern to the arrival of these meteorites and how they explode upon entry into the atmosphere. More importantly, it offered clues on its path, origin and the power and damage of the so called airbust, the event that caused the explosive outburst that shattered building windows and doors for miles, and illuminated the sky like a giant fireball.
What is most interesting to scientists at this point, is to figure out what is the average frequency of these events. Theoretical mathematical models could predict some of the events early enough to mitigate the possible impact on the population.
Using the positions of the stars, the authors determined from night shots, that the Chelyabinsk meteorite originated in the Asteroid Belt that circulates between Mars' and Jupiter's orbits. A similar trajectory was observed in a previous meteor in 1999, denoted as 860389, that took trajectory close to Earth's space.
Scientists now believe that the 1999 meteor and the Chelyabinsk object may have been one and the same, with the Chealybinsk object being the remnant of the larger 1999 one. That meteor was almost 2.2 km in diameter, which, if it had entered the atmosphere intact, would have had a catastrophic effect.
Of that very large meteor, called a superbolide, of 1999, the Chelyabinsk remnant was a minute 19 metres in diameter, which immediately gives a measure of what devastation a larger object could wreak.
What is however, of concern, is that there might be more of the 1999 meteor fragments that are orbiting the Earth in a freefall trajectory. Small objects such as the Chelyabinsk meteorite are very difficult to track via telescopes, because of their small size in the vatness of space.
The Chelyabinsk event, although modest in comparison to prehistoric events, or possible future ones, also offered a glimpse on what the additional effects of the airburst had on the planet. One of the interesting observations during the event was that the airburst sent a 'ringing' sound all across the globe, that was registered by instruments that are placed in the ground to detect covert nuclear explosions, some of them as far as 6000 km away from Chelyabinsk.
One of the ways scientists are now trying to predict the possibility of further events is by measuring how the energy outburst from Chelyabinsk can be a predictor of future events. In a way, the meteorite's fast moving track dispersed the explosive energy released along a narrow and stretched out path, which diminished its potency. That is good news for future events, but what is not good news, is that the number of meteorites or fragments that are possibly going to strike Earth is much larger than previously estimated from data that did not inlcude real events like Chelyabinsk.
Source : 11.07.13
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