Remains of the Chelyabinsk meteor
The Chelyabinsk meteorite (Russian: Челябинский метеорит, "Chelyabinskii meteorit") is the fragmented remains of the large Chelyabinsk meteor of 15 February 2013 which reached the ground after the meteor's passage through the atmosphere. The descent of the meteor, visible as a brilliant superbolide in the morning sky, caused a series of shock waves that shattered windows, damaged approximately 7,200 buildings and left 1,491 people injured. The resulting fragments were scattered over a wide area.
The largest fragment raised from the bottom of Lake Chebarkul on 16 October 2013 had a mass of and the total mass of other 7 meteorite fragments found nearby was .
Naming.
The meteor and meteorite are named after Chelyabinsk Oblast, over which the meteor exploded. An initial proposal was to name the meteorite after Lake Chebarkul, where one of its major fragments impacted and made a hole in the frozen lake surface.
Composition and classification.
The meteorite has been classified as an LL5 ordinary chondrite. First estimates of its composition indicate about 10% of meteoric iron, as well as olivine and sulfides.
Asteroid.
The impacting asteroid started to brighten up in the general direction of the Pegasus constellation, close to the East horizon where the Sun was starting to rise. The impactor belonged to the Apollo group of near-Earth asteroids.
The asteroid had an approximate size of and a mass of about before it entered the denser parts of Earth's atmosphere and started to ablate. At an altitude of about 23.3 km (14.5 miles) the body exploded in a meteor air burst. Meteorite fragments of the body landed on the ground.
Analysis of three fragments using optical microscopy, electron microscopy, Raman spectroscopy, and isotopic composition techniques used to date Solar System objects, showed the isotopic clocks in the asteroids (rubidium and strontium ratios, argon isotope ratios) appear to have partially or totally reset in past collisions. The isotopic clock resets may result from thermal effects changing isotopic ratios, and changes due to cosmic radiation exposure. The asteroid appears to have had eight major collisions, around 4.53, 4.45, 3.73, 2.81, and 1.46 billion years ago, then at 852, 312, and 27 million years ago.
Meteorite.
Scientists collected 53 samples from near a hole in the ice of Lake Chebarkul, thought to be the result of a single meteorite fragment impact. The specimens are of various sizes, with the largest being , and initial laboratory analysis confirmed their meteoric origin.
In June 2013, Russian scientists reported that further investigation by magnetic imaging below the location of the ice hole in Lake Chebarkul had identified a meteorite buried in the mud at the bottom of the lake. An operation to recover it from the lake began on 10 September 2013, and concluded on 16 October 2013, with the raising of the rock with the mass of . It was examined by scientists and handed over to the local authorities, who put it on display at the Chelyabinsk State Museum of Local Lore.
In the aftermath of the superbolide air burst, a large number of small meteorite fragments fell on areas west of Chelyabinsk, including Deputatskoye, generally at terminal velocity, about the speed of a piece of gravel dropped from a skyscraper. Local residents and schoolchildren located and picked up some of the meteorites, many located in snowdrifts, by following a visible hole that had been left in the outer surface of the snow. Speculators became active in the informal market for meteorite fragments that rapidly emerged.
References.
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