Russian meteor was partially formed from hard to spot 'dark asteroid' material Dr Tomas Kohout, fro the University of Helsinki, Finland, and Dr Maria Gritsevich, from the Finnish Geodetic Institute and Russian Academy of Science found the meteor was made from silicate rich chondrites - a stony conglomerate. Around two thirds of the fragments found seemed to be bright grey coloured ordinary chondrites, but a third was a black chondrite material. Dr Kohout said that the black material in the fragments contain signatures of the violent collisions that occurred early in the asteroid's history. He said: "The composition of Chelyabinsk meteorites correspond to so called undifferentiated ordinary chondrites. This material originated early in Solar System around 4.6 billion years ago and did not undergo significant mineralogical changes since its formation. What makes Chelyabinsk meteorites unique is that different fragments of the identical composition experienced various shock levels. Thus we can study how shock - caused by ancient space collisions - is changing properties and appearance of meteorites and asteroid surfaces. The Chelyabinsk parent body collided in ancient history with other planetary object. This collision is responsible for shock darkening. Most likely, the darker material was closer to the impact point than the less shocked brighter material. The scientists also hope that by studying the meteor fragments they may be able to adapt new strategies for spotting and tracking dark asteroids. Currently Nasa's Near Earth Objects Programme is currently tracking 10,303 comets and asteroids, of which 1,425 have been classified as potentially hazardous asteroids to the Earth. Most asteroids are now tracked using radar although some are still spotted using visible light and in a vast area of the sky detecting all objects passing near the Earth can be difficult. Dr Kohout said: "Dark asteroids are harder to detect because they reflect less light. While ordinary stony asteroids similar to bright Chelyabinsk meteor reflect roughly 15-20% of solar light, the dark asteroids reflect around 5% or even less. Thus, it is hard to detect small dark asteroids. Earlier this year scientists announced they had managed to track the origins of the Chelyabinsk meteor as having broken off a 656 feet wide asteroid called 2011 EO40. This large asteroid is a so-called Apollo asteroid, which regularly crosses the path of the Earth as it orbits around the sun, and has been listed as a potentially hazardous asteroid. "Such large asteroids collide with Earth approximately once in 100 years," said Dr Gritsevich. They come usually without any warning and can cause significant local damage. Luckily for the residents of the Chelyabinsk region, the asteroid disintegrated high in the atmosphere, saving the Earth this time from a more catastrophic impact. Dr Kohout and Dr Gritsevich are now to present their latest findings to the American Astronomical Society Division for Planetary Sciences meeting in Denver, Colorado. The results help to shed light on potentially hazardous impacts of asteroids on Earth, but also on more violent space collisions that occurred in the early solar system. "These dark meteorites are exciting rocks to study," said Dr Kohout. Their spectrum and composition is masked by ancient space collisions. There are many dark asteroids with featureless spectra in our solar system. Some people think that they may be formed of rocks rich in carbon and organic matter. But they can be also made of shock-darkened ordinary chondrites similar to the dark Chelyabinsk meteorites. It may explain why we cannot identify the composition of dark asteroids. We need spacecraft to visit asteroids and return samples back to our laboratories.