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METEOR dawn meets social media over Siberia

At Chelyabinsk we have glimpsed the risks that fill our place in the cosmos. They will challenge our species, one way or another, for the rest of our days.

Social media image: Double headed meteor trail over Urals

It may have only packed a punch one thousandth of that of the Tunguska Meteor of 1908, but the double headed meteor dawn that injured hundreds of people at Chelyabinsk in the central Russia Urals yesterday was recorded by hundreds of hand held and automated cameras when it lit up the pre dawn twilight.

Those images, and the supersonic shock wave that broke windows and even collapsed some factory walls, fulfilled, in a comparatively minor way, the prophecy of many astronomers that as humanity spreads itself further across the planet it would eventually get hit by the rolling of the cosmic dice of meteors, and larger earth crossing objects.

An initial assessment by NASA has been reported as follows on Spaceweather.com

NASA scientists have conducted a preliminary analysis of the event. “Here is what we know so far,” says Bill Cooke, head of NASA’s Meteoroid Environment Office. “The asteroid was about 15 meters in diameter and weighed approximately 7000 metric tons. It struck Earth’s atmosphere at 40,000 mph (18 km/s) and broke apart about 12 to 15 miles (20 to 25 km) above Earth’s surface. The energy of the resulting explosion was in the vicinity of 300 kilotons of TNT.” (continued below)

“A shock wave propagated down and struck the city below, causing large numbers of windows to break, some walls to collapse, and minor damage throughout the city,” he continued.

“When you hear about injuries, those are undoubtedly due to the effects of the shock wave, not due to fragments striking the ground. There are undoubtedly fragments on the ground, but as of this time we know of no recovered fragments that we can verify.”

By way of comparison the Tunguska event, which coincided with earth’s annual passage through the debris trail of ‘dead’ Comet Encke , is estimated to have released between 5-30 Megatonnes equivalent of TNT.

Whatever the amount, Chelyabinsk was much less powerful in energy released, with only the shockwave carried energy reaching the ground while the heat that reputedly set fire to a goatherds jacket at a distance of 200 kilometes in 1908 off a far larger meteor caused fireball was absorbed by the stratosphere.

Yet the TNT equivalent of the Hiroshima and Nagasaki atom bombs is usually quoted at 12.5 kilotonnes, making Chelyabinsk much more powerful than those devices, but which were detonated close to the ground, and not at altitudes far higher than cruised by the Concordes.

These social media records, and the physical damage to structures, will allow refined estimates of the force of Chelyabinsk in coming days. One of the most violent of the videos captured multiple very sharp supersonic whip crack overloads over a period of about three seconds, after which the images are full of blurred outlines of people running from falling masonry and fittings.

Some of the other videos are, according to translations, taken from inside taxis using security systems when the early morning peak hour darkness suddenly flares into noon day brilliance as the fireball moves from east to west.

One collection by Alexander Zaytsev includes the fireball as seen from as much as 770 kilometres from ground zero, or 300 kilometres away as shown in this frame:

In another video, where the sky is darker and meteor higher above the horizon the moment of maximum decceleration is captured at the point where the meteor gives up most of its kinetic energy in an expanding and slowing fireball. A space rock is dropping from 18,000 metres per second to ‘only’ a few thousand metres per second, and its kinetic energy is being dissipated mainly into the stratosphere.

However far below it at a snowy intersection the passage of the meteor is like a gigantic spotlight, creating fast moving shadows.

In a school the corridors are crammed full of students bolting for the exists.

Posting on his LiveJournal page, Ilya Varlamov combined some almost artistic photos of the debris trail in the atmosphere with the chaos and panic on the ground.

This truck driver view of damage is on the outskirts of Chelyabinsk.

Also on the the city’s edges, this was the damage inside an office.

If this meteor had been as large and high speed in its intersecting trajectory with earth as the object that exploded over the Tunguska River far to the east of Chelyabinsk almost 105 years ago  we would not have hundreds of reportedly minor injuries, but more than one million dead people and as many more severely burned in what would be a massive crisis in an area suddenly without electricity, heating and fresh water.

And social media would not have been documenting the disaster close up. It would have died with its users, or at best its records been recovered after the event from those devices that were capable of being read and downloaded in the aftermath.

At Chelyabinsk we have glimpsed the risks that fill our place in the cosmos. They will challenge our species, one way or another, for the rest of our days.

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  • 1
    chpowell
    Posted February 16, 2013 at 3:38 pm | Permalink

    Great coverage, Ben, including the Tunguska comparison.

  • 2
    COTOS
    Posted February 17, 2013 at 10:16 pm | Permalink

    yes nicely wordsmithed, and i suppose right now somewhere out there is a large frozen dark rock that eventually will cross our path that no dash cam on the planet will survive, not even inside a Lada, hopefully social media will capture it but this time from a bunker or window of a fleeing spacecraft.

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