Chelyabinsk meteorite parent body collided with asteroid before hitting Earth
Several fragments of Chelyabinsk meteorite found in Russia last year show a clear evidence for an intense impact event to its parent body. This impact might have separated Chelyabinsk asteroid and point it in our direction.
On February 15, 2013, a 17 – 20 meters wide asteroid entered the Earth's atmosphere and exploded about 30 km above the Chelyabinsk city, Russia. The blast caused significant damage in the city, breaking thousands of windows and injuring more than 1 000 people. It is the second largest asteroid airburst in our recorded history. The first one is Tunguska event of 1908.
According to a new analysis of Chelyabinsk meteorite fragments, published in Nature on May 22, 2014, an impactor larger than 0.15 – 0.19 km in diameter collided with the Chelyabinsk parent body at a speed of at least 0.4 – 1.5 km/s.
"In orbital evolution of an asteroid, collision with other asteroids is a key process. Here, we show the existence of a high-pressure mineral jadeite in shock-melt veins of Chelyabinsk meteorite. Based on the mineral assemblage and calculated solidification time of the shock-melt veins, the equilibrium shock pressure and its duration were estimated to be at least 3–12 GPa and longer than 70 ms, respectively…
Shock-melt veins are formed by localized melting of materials during an impact due to concentration of stress, compaction of pores, or frictional heating. In shock-melt veins, both high-pressure and high-temperature conditions can be achieved simultaneously under shock, where constituent minerals can transform to their high-pressure polymorphs."
In this study, we carefully examined several fragments of Chelyabinsk meteorite containing shock-melt veins in order to clarify the magnitude of the impact event occurred on its parent asteroid. We found a clear evidence for an intense impact event: the existence of a high-pressure mineral jadeite in Chelyabinsk meteorite.
Back-scattered electron images of Chelyabinsk meteorite samples
(a) The host-rock showing an equilibrated chondrite texture. (b) A shock-melt vein cutting through the host-rock. The two white dotted lines represent the boundaries between them. (c) Coarse-grained fragments and fine-grained matrix in a shock-melt vein. (d) Enlarged view of the area shown by the white rectangular in (c). Needle-like and skeletal-rhombic crystals of jadeite occur with feldspathic glass. Ol = olivine, En = enstatite, Di = diopside, Fsp = albitic feldspar, Me = Fe–Ni metal, Tro = troilite, Chr = chromite, SMV = shock-melt vein, Mtx = matrix of shock-melt vein, Jd = jadeite, Gl = feldspathic glass. Figure 1. – Nature / Jadeite in Chelyabinsk meteorite and the nature of an impact event on its parent body
The Russian meteor's infrasound signal was was the strongest ever detected by the CTBTO network whose purpose is to monitor nuclear explosions. The furthest station to record the sub-audible sound was 15 000 km away in Antarctica.
Reference:
"Jadeite in Chelyabinsk meteorite and the nature of an impact event on its parent body" – OPEN ACCESS – Authors: Shin Ozawa, Masaaki Miyahara, Eiji Ohtani, Olga N. Koroleva, Yoshinori Ito, Konstantin D. Litasov & Nikolay P. Pokhilenko – Nature – Scientific Reports 4, Article number: 503 3- doi:10.1038/srep05033
Featured image: Chelyabinsk meteor on February 15, 2013.
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