As if asteroid 2012 DA14 making a record close pass by the Earth was not enough, a meteor explodes with the force of an atomic bomb near Chelyabinsk, Russia. Wow! What a day for the history books. We are reminded again of the devastation relatively small space rocks can bring.
Asteroid 2012 DA14 is the closest (17,154 miles) object of its size (150 feet) to pass by the Earth. Any time an object comes within the orbit of the Moon it’s a close call. If you missed the live video you can watch it here from several different observatories some of which operated by amateur astronomers.
It will probably be several months before we find out just how lucky we earthlings really were on the Chelyabinsk event. The size of the explosion is estimated to be in the 470 kilotons range. To put that into perspective, that’s thirty times the explosive force of the atomic bomb dropped on Hiroshima. On that morning in August 1945 80,000 people were killed instantly, and another 70,000 were injured as a result of the blast. Anything within a mile of the center of the blast was totally destroyed. If the meteor had exploded over Chelyabinsk the carnage would have been unimaginable. Fortunately the city was far enough away to get only “minimal” blast effects; enough to break windows, and knock people to the ground.
Russia has experienced two other such events. Tunguska was the largest. The recent Chelyabinsk event ranks a far second behind it.
Tunguska, Siberia June 30, 1908 the largest impact or near-earth explosion was recorded. The meteor or comet was estimated to be twice the size (300 feet) of asteroid 2012 DA14. 80,000,000 trees were destroyed over and 800 square mile area. The blast estimates range from 5 to 30 megatons or 300 to 1800 times the Hiroshima bomb. Tunguska is very remote, No one was reported killed, but people 60 miles away were knocked to the ground from the blast.
Sikhote-Alin meteorite blew up on February 12, 1947 near Luchegorsk, Russia some 270 miles northeast of Vladivostok. This was the first time such an impact was observed. The 100 ton meteor hit the atmosphere going over 31,000 miles an hour. A twenty mile smoke trail was observed for several hours. 25 tons of material broke off and impacted the ground as several impact craters. The largest was 85 feet across and 20 feet deep. Fragments of the meteor were found imbedded in trees.
Just how often do these events happen? It’s more often than one may think. Here is a list of meteor air bursts starting in 1899. The probability of another Tunguska/ Chelyabinsk event is about one in hundred years. Over a densely populated area the chances are far more remote. Most will simply go into the ocean.
Wishing you clear skies
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