October 16, 2013
Largest Yet Chelyabinsk Meteorite Fragment Raised From Lakebed
[ Watch the Video: Divers Recover Huge Russian Meteorite Fragment ]
Lawrence LeBlond for redOrbit.com - Your Universe Online
Divers searching Lake Chebarkul in Russia have pulled from the lakebed a massive chunk of the Chelyabinsk meteorite that exploded over the Ural Mountains region earlier this year.
On February 15, 2013 a massive meteor entered Earth’s atmosphere, traveling at speeds in excess of 30,000 mph. As it blazed a trail across the early morning sky, many videos caught the fireball on its journey, before it exploded and sent a massive shockwave over the Earth, shattering thousands of windows and injuring more than 1,500 people.
Once things settled down and experts got a handle on what exactly happened, meteorite hunters began a mad dash to recover fragments and pieces of the space rock that caused the Chelyabinsk region so much mayhem on that cold day in February. The popular consensus was that the bulk of the space rock crashed into Lake Chebarkul after it exploded; with this knowledge in hand, the majority of searches were focused in that area.
In the months that followed, several pieces of meteorite have been discovered, with most fragments weighing just a few ounces to a few pounds, with the largest weighing nearly 25 pounds. However, the newest fragment, pulled from the lake this week, is the single largest specimen yet to be attributed to this event. The fragment was so big that it broke into three sections when experts tried to weigh it. Not being able to get a precise measurement, the scientists estimated that it weighed in the neighborhood of 1,256 pounds (570 kg).
“The preliminary examination... shows that this is really a fraction of the Chelyabinsk meteorite. It’s got thick burn-off, the rust is clearly seen and it’s got a big number of indents. This chunk is most probably one of the top ten biggest meteorite fragments ever found,” said Sergey Zamozdra, associate professor of Chelyabinsk State University, as cited by Interfax news agency.
He noted that it is very important to establish the weight of the meteorite fragment to better understand its qualities as a whole. After being raised from the lakebed, the rock was taken to the regional natural history museum for x-ray and analysis to determine what minerals it consists of.
The fragment was discovered in September, but it has taken experts several attempts to successfully lift it from the bottom of the lake. Early efforts were hampered because the chunk of rock was mired in a thick layer of mud some 70 feet down. It took a team 10 days just to pump out enough mud to allow divers to get to the rock, a task made much more difficult by zero visibility conditions in the muddy waters. A barrage of storms hampered their attempts as well.
Since researchers and divers have descended upon the lake, 12 alleged pieces of meteorite have been raised from the lakebed. So far, only five of them have been confirmed as meteorite fragments.
The latest find was confirmed as a meteorite by Dr. Caroline Smith, curator of meteorites at London’s Natural History Museum.
She said fusion crust and regmaglypt impressions were telltale characteristic features of the fragment.
"Fusion crust forms as the meteoroid is traveling through the atmosphere as a fireball,” she said in an interview with the BBC. "The outer surface gets so hot it melts the rock to form a dark, glassy surface crust which we term a fusion crust. Regmaglypts are the indentations, that look a bit like thumbprints, also seen on the surface of the meteorite."