Chelyabinsk meteorite may have had prior collision before impact
Washington: Chelyabinsk meteorite had either earlier collided with another body in the solar system or came too close to the Sun before it fell to Earth, according to a new research.
A team from the Institute of Geology and Mineralogy (IGM) in Novosibirsk have analysed fragments of the meteorite, the main body of which fell to the bottom of the Chebarkul Lake near Chelyabinsk on February 15 this year.
Although all of the fragments are composed of the same minerals, the structure and texture of some fragments show that the meteorite had undergone an intensive melting process before it was subjected to extremely high temperatures on entering the Earth`s atmosphere.
Dr Victor Sharygin from IGM, who is presenting the research at the Goldschmidt conference, said that the meteorite which landed near Chelyabinsk is a type known as an LL5 chondrite and it`s fairly common for these to have undergone a melting process before they fall to Earth.
He said that this almost certainly means that there was a collision between the Chelyabinsk meteorite and another body in the solar system or a near miss with the Sun.
Based on their colour and structure, the IGM researchers divided the meteorite fragments into three types: light, dark and intermediate.
The lighter fragments are the most commonly found, but the dark fragments are found in increasing numbers along the meteorite`s trajectory, with the greatest number found close to where it hit the Earth.
The dark fragments include a large proportion of fine-grained material, and their structure, texture and mineral composition shows they were formed by a very intensive melting process, likely to have been either a collision with another body or proximity to the Sun.
This material is distinct from the `fusion crust` - the thin layer of material on the surface of the meteorite that melts, then solidifies, as it travels through the Earth`s atmosphere.
Sharygin said that of the many fragments we`ve been analysing, only three dark samples show strong evidence of earlier metamorphism and melting.
He asserted that however, many fragments of the meteorite were picked up by members of the public, so it`s impossible to say how large a portion of the meteorite was affected.
Sharygin said that they hoped to find out more once the main body of the meteorite is raised from Chebarkul Lake.
The fine-grained material of the dark fragments also differs from the other samples as it commonly contains spherical `bubbles,` which are either encrusted with perfect crystals of oxides, silicates and metal or filled with metal and sulphide.
The team are only able to identify these elements as an alloy of osmium, iridium and platinum, but its presence is unusual as the fusion crust is formed over too short a time period for these elements to easily accumulate.
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